Note: Descriptions are shown in the official language in which they were submitted.
CA 02349017 2001-06-12
FORI<IULATIONS AND 1~IETfiODS FOR PROVIDING
PROLONGED LOCAL ANES1'IiESIA
BACKGROUND OF TfIE INVENTION
The present invention is related to biodegradable controlled release formula-
s tions for the administration of locally active drugs, in particular, local
anesthetics
and compositions and methods for augmenting the potency and duration of the
same.
While compounds utilized as general anesthetics reduce pain by producing a
loss of consciousness, local anesthetics act by producing a loss of sensation
in the
localized area of administration in the body. The mechanism by which local
anesthetics induce their effect, while not having been determined
definitively, is
generally thought to be based upon the ability to interfere with the
initiation and
transmission of the nen-e impulse. The duration of action of a local
anesthetics is
proportional to the time d~rring which it is in actual contact with the
nervous tissues.
Consequently, procedures or formulatior» that maintain localization of the
drug at
the nerve greatly prolong anesthesia.
All local anesthetics acre toxic, i.e., potentially toxic, and therefore it is
of
great importance that the choice of drug, concentration, rate and site of
administration, as well as other factors, be considered in their use. On the
other
hand, a local anesthetic must remain at the site long enough to allow
sufFrcient time
for the localized pain to subside.
Different devices and formulations are known in the art for administration of
local anesthetics. For example, U.S. Patent Nos. 4,x25,442 and 4,622,219
(Haynes) are directed to microdroplets of methoxyflurane-containing
microdroplets
coated with a phospholipid prepared by sonication, which are suitable for
intradermal or intravenous injection into a patient for inducing local
anesthesia.
Such microdroplets are said to cause long-term local anesthesia when injected
intradermally, giving a dur~rtion of anesthesia considerably longer t',ran the
longest
acting conventional local anesthetic (bupivacaine).
CA 02349017 2001-06-12
U.S. Patent No. 5,188,8;7 (Domb) relates to a microsuspension system
containing lipospheres havinf; a layer of a phospholipid imbedded on their
surface.
The core of the liposphere is a solid substance to be delivered, or the
substance to
be delivered is dispersed in an inert vehicle. The substance to be delivered
can be,
e.g., nonsteroidal anti-inflammatory compounds, local anesthetics, water
insoluble
chemotherapeutic agents and. steroids.
Other formulations directed to injectable microcapsules, etc. are known.
For example, U.S. Patent No. 5,061,492 related to prolonged release
microcapsules
of a water-soluble drug in a biodegradable polymer matrix which is composed of
a
to copolymer ofglycolic acid and a lactic acid. The microcapsules are prepared
as an
injectable preparation in a pharmaceutically acceptable vehicle. The particles
of
water soluble drug are retained in a drug-retaining substance dispersed in a
matrix
of the lactic/glycolic acid copolymer in a ratio of 100/1 to SO/SO and an
average
molecular weight of 5,000-200,000. The injectable preparation is made by
preparing a water-in-oil ennulsion of aqueous layer of drug and drug retaining
substance and an oil layer of the polymer, thickening and then water-drying.
U.S. Patent No. 4,M'9.3,539 (Ludwig, et al.) is directed to controlled release
formulations comprised of a microbial agent dispersed throughout a copolymer
derived from lactic acid and p~lycolic acid. The copolymer is derived from 60-
95%
lactic acid and 40-5% glycolic acid by weight, and has a molecular weight of
6,000-
35,000. An effective amount of the copolymeric formulation is administered by
subcutaneous or intramuscular administration.
WO 94/05265 describes improved biodegradable controlled release systems
consisting of a polymeric matrix incorporating a local anesthetic for the
prolonged
administration of the local anesthetic agent. The devices are selected on the
basis of
their degradation profiles: release of the topical anesthetic in a linear,
controlled
manner over the period of preferably two weeks and degradation in vivo with a
half life of less than six nu~nths, more preferably two weeks, to avoid
localized
inflammation. The disclosure states that an anti-inflammatory can be
incorporated
CA 02349017 2001-06-12
3
into the polymer with the local anesthetic to reduce encapsulation for optimal
access of drug to its site of action. The anti-inflammatories that are said to
be
useful include steroids su<;h as dexamethasone, cortisone, prednisone, and
others
routinely administered orally or by injection.
Several non-glucocorticoids have been reported to prolong the action of
local anesthetics. Epinepluine in immediate release form is art known to
briefly
prolong the action of immediate release local anesthetics by inducing
vasoconstriction adjacent to the site of injection. However, the duration of
prolongation provided by immediate release epinephrine is on the order of
about an
hour, at best, in a highly vasc:ularized tissue. This strategy is also
severely limited
by the risk of gangs ene due to prolonged impairment of blood flow to local
tissues.
Dextrans and alkalinizing agents have also been suggested as local anesthesia
prolonging agents, but have heretofore been reported to be ineffective for
this
purpose (Bonica et al., 1990, ''Regional Analgesia With Local Anesthetics" THE
MA.'~AGEMENT OF PATH, Second Edition, Volume II, Published, Lea & Febiger,
Chapter 94, pages I890-1892)
Colchicine has been shown to suppress injury-induced ectopic nerve
discharge in a model system of chronic pain utilizing injured nerve (Wall et
al.
(Eds), 1995, Textbook of Lain, Third Edition, Publ., Churchill Livingston,
pages
94-98; Devol et al., 1991, .A Group Report: Mechanisms of neuropathic pain
folfowin~ peripheral iniurv. l:n: l3asbaume A I, et al (eds). TowARDS A NEw
Pt-~.RMACO'I~-IERA.~Y OF P~IrJ, Dahlem Konferenzen, ~Viley, Chichester pp 417-
440; Devor et al., 1985, Pain, 22:127-137 at 128 and Devor, 1983, Pain. 16:73-
86).
It has been reported in one study that colchicine was given for the treatment
of low-
back pain, although oral cctlchicine has been shown to be ineffective for the
same
indication (Schnebel et al., 1988, Spine 13(3):354-7). However, it has not
heretofore been known to use Colchicine to prolong local anesthesia.
CA 02349017 2001-06-12
4 --
Thus, it has not previously been known to combine or otherwise administer both
a
controlled release local anesthetic and a non-glucocorticosteroid agent for
augmenting
the duration of local anesthesia.
SUMrMARY OF TI-IE INVENTION
The present invention provides a biodegradable controlled release dosage form
for
providing prolonged local anesthetic treatment of localized areas in humans
and animals.
More particularly, the invention provides a local anesthetic in a
biocompatible,
biodegradable controlled release farm which provides a prolonged local
anesthesia.
The invention provides a formulation for inducing sustained regional local
anesthesia or analgesia in a patient comprising:
a plurality of substrates in a pharmaceutically acceptable medium for
injection,
said substrates comprising a local anesthetic and an effective amount of a
biocompatible,
biodegradable controlled release material comprising a polymer selected from
the group
consisting of polyanhydrides, copolymers of lactic acid and glycolic acid,
poly(lactic)
acid, poly(glycolic) acid, polyesters, po(yorthoesters, proteins,
polysaccharides and
combinations thereof, said biocompatible, biodegradable controlled release
material
being capable of degrading at iea.st fifty percent in less than two years
following
implantation or injection into the patient and prolonging the release of said
local
anesthetic from said substrates in-vitro, said substrates being included in
said
formulation in an amount sufficient to obtain reversible local numbness or
analgesia
when said formulation is implanted or injected in a patient, and an augmenting
agent
selected from the following:
(i) a vasoconstricting agent selected from the group consisting of
catecholamines, alpha-1 and alpha-2 adrenergic agonists, analogs thereof,
active
metabolites thereof, and mixtures thereof, said vasoconstricting agent being
effective to
prolong the duration of said local anesthesia for a time period longer than
that obtainable
from said substrates without said vasoconstricting agent and included in a
ratio from
about 10:1 to about 20,000:1 relative to said local anesthetic, or
(ii) a modulator of ionic transport across cell membranes; or
(iii) a tubulin binding agent; or
(iv) a sodium/potassium ATPase inhibitor; or
CA 02349017 2001-06-12
4a
(v) a neuroactive steroid
said augmenting agent being; (i) incorporated into or onto said substrates; or
(ii)
incorporated into said pharmace:u~~~:ically acceptable medium for injection,
or (iii)
incorporated into said substrates and also incorporated into said
pharmaceutically
acceptable medium for injection.
Further, the present invention provides a method for prolonging the effect of
a
local anesthetic agent at a desired site of treatment which is save,
effective, and which
effectively controls post-operative; pain. Still further, the invention
prolongs the duration
of the local anesthesia produced by administering an augmenting agent, before,
during
or after administration of a local .anesthetic according to the invention, to
a topical site
or after infiltration, injection or implantation of the compositions according
to the
invention
In accordance with the above-mentioned aspects and others, the invention is
related to biodegradable and/or biaerodable controlled release formulations
for the
administration of a local anesthetic agent capable of providing a prolonged
effect in
vivo, in combination with a pharmaceutically acceptable augmenting agent which
is
effective to prolong the duration of the local anesthetic effect for a time
period greater
than that possible by the use of the local anesthetic in controlled release
form by itself
(without the augmenting agent) and methods for the manufacture thereof are
disclosed.
The controlled release formulation can be formed into slabs, rods, pellets,
microparticles, (e.g., microspheres, microcapsules), spheroids and pastes.
Preferably,
the formulation is in a form suitable for suspension in isotonic saline,
physiological
buffer or other solution acceptable for injection into a patient.
CA 02349017 2001-06-12
The invention further provides methods for inducing localized anesthesia by
implanting, inserting or injecting a controlled release formulation, e.g., in
the form
of injectable microspheres loaded with a local anesthetic in sustained release
form,
into a site at or adjacent to a nerve or nerves innervating a body region to
provide
5 local anesthesia. Thus, the controlled release formulation according to the
invention must be applied, injected, infiltrated or implanted at a site in a
patient
where the local anesthetic agent is to be released.
Further aspects of the invention are directed to a method of treating a
patient in need of a surgical procedure, comprising placing a local anesthetic
in
controlled release form in proximity to a nerve or nerves at a site to be
anesthetized,
e.g., a surgical site, and previously, simultaneously and/or subsequently
administering the aforementioned augmenting agent to substantially the same
site to
attain a prolongation of local anesthesia otherwise unattainable via the use
of the
local anesthetic alone.
The invention also provides for a unit dosage of the controlled release
formulation comprising, in a container, a sufficient amount of the formulation
to
induce and/or prolong local anesthesia in at least one patient. In one
embodiment,
the unit dosages are sterile and lyophilized. Alternatively, the unit dosages
are
sterile and prepared as a suspension in a solution acceptable for injection
into a
2 0 patient.
The invention is further directed in part to novel formulations for providing
local anesthesia, comprising a pharmaceutically-acceptable local anesthetic
agent or
a mixture of multiple difFerent local anesthetic agents, in controlled release
form,
said formulation being capa.bl~~ of being placed in proximity to a nerve which
is to
2 5 be anesthetized, and an effect ive amount of a augmenting agent capable of
prolonging the localized anesthetic effect provided by the local anesthetic in
controlled release form. Tlre augmenting agent may be incorporated with the
local
anesthetic in controlled release form, or alternatively, at least part of the
dose of the
augmenting agent may be administered separately but in proximity to the same
CA 02349017 2001-06-12
location as the local anesthetic. At least a pan of such a separate dose may
be
administered later in time than the local anesthetic, to provide additional
augmentation of the extent and/or duration of the local anesthetic effect. A
portion
of the local anesthetic can be administered to the desired site in immediate
release
form as long as a portion of the: local anesthetic is also administered in
controlled
release form. On the other hand, the augmenting agent can be administered to
substantially the same site at the same time as the local anesthetic, at a
later time
than the local anesthetic, or both, so long as the nerve blockade effect of
the local
anesthetic is substantially prolonged as compared to that which would be
obtained
with the local anesthetic alone.
In certain preferred embodiments of the invention, the local anesthetic is
prepared in matrices of biodegradable controlled release injectable
microspheres.
Optionally, the augmenting agent is incorporated into these matrices along
with the
local anesthetic.
In further embodiments, the invention is directed to a suspension comprising
a plurality of biocompatible, k~iod~gradable controlled release microspheres
comprising a local anesthetic agent, together with an augmenting agent which
is
incorporated in the controlled rf:lease microspheres, or dissolved or
suspended in
the suspension of microsphercs. 1'he suspension is, for example, suitable for
2 0 administering the microspheres lby injection.
In yet additional embodiments of the present invention, the local anesthetic
is incorporated into a controlled release matrix having the augmenting agent
coated
on the surface thereof
In yet additional embodiments of the invention, the formulation comprises a
2 5 local anesthetic core; an augmenting agent present in the core in an
amount
effective to prolong the effect oi~the local anesthetic in an environment of
use, and a
biocompatible, biodegradable coating on the core providing a slow release of
the
local anesthetic and/or augmenting agent in an environment of use.
CA 02349017 2001-06-12
7
In further embodiments, a portion or all of the local anesthetic is
incorporated onto an outer surface of the coated substrate and a portion or
al( of
the augmenting agent is optionally incorporated in the core, so that, e.g.,
augmenting agent continues to be released after the local anesthetic has
dispersed
from the controlled release material.
Where the local ancathetic is applied topically to epidermal and/or mucosal
surfaces, the augmenting agent may also be topically applied before, after or
simultaneously with the focal anesthetic.
The augmenting agent may be systemically administered by injection or
infiltration, instillation, oral dosing or other method to obtain the desired
prolongation of effect. Systemic administration, (e.g., oral or intravenous)
while
effective, will require a higher total dose of an augmentation agent tha.~
with local
administration in proximity to the local anesthetic.
The controlled release local anesthetic dosage form may be injected or
infiltrated, with or W thout an augmenting agent, at the site where the
anesthetic is
to be released. This can be prior to surgery, at the tine of surgery, or
following
removal (discontinuatiory) or reversal of a syste;nic anesthetic.
In one preferred embodiment, the formulation is prepared in the form of
microspheres. The micros;pheres may be prepared as a homogenous matrix of a
local anesthetic with a biodegradable controlled release material, with the
augmenting agent optionally incorporated therein. The microspheres are
preferably
prepared in sizes suitable fir infiltration and/or injection, and injected at
the site
where the anesthetic is to be released before surgery, during the time of
surgery, or
following removal or reversal of systemic anesthetic.
2 5 Augmenting agent<.; according to the present invention are
pharmaceutically
acceptable agents and include, for example, alkalinizing agents, non-
glucocorticoid
steroids such as neuroactive steroids, modulators of gamma amino butyric acid
receptors, modulators of ionic transport across cell membranes, antipyretic
agents,
adrenergic receptor agonis,ts or antagonists, tubulin binding agents, osmotic
CA 02349017 2001-06-12
8
polysaccharides, agonists and antagonists of potassium ATP channels, Na, K-
ATPase inhibitors and enhanc:ers, neurokinin antagonists, phosphatidylinositol-
specific phospholipase C ("PL.C") inhibitors, inhibitors of leukocyte glucose
metabolism, anti-conwlsants, analeptics, a tranquilizing agent,
antidepressant, an
conwlsant, leukotriene and prostaglandin agonists and inhibitors,
phosphodiesterase agonists and inhibitors, vasoconstrictive agents in
sustained
release form and combinations of any of the foregoing.
Examples demonstrate; prolongation of the duration of local anesthesia with
the greater prolongation bein~; provided by the combination of a local
anesthetic
l0 with a non-glucocorticoid augmenting agent.
DE'TAII,ED DESCRIPTION
Accordingly, the present invention provides for pharmaceutically acceptable
augmenting agent or agents in conjunction with a local anesthetic in
controlled
release form that significantly increases the time period of local anesthesia
when
administered at a site in a patif:nt. The augmentation of efficacy provided by
the use
of the augmenting agent cannot be predicted based on in vitro release
(dissolution)
of the local anesthetic in controlled release form: the inclusion of the
augmenting
agent within the controlled release formulations of the invention does not
2 o substantially alter or prolong tlhe in vitro dissolution rate of the local
anesthetic
agent from the formulation; yet, the same formulation when administered in
vivo
provides a significant increase in the time period of local anesthesia at the
site of
administration. The augmenting agents disclosed herein are non-glucocorticoid
agents and can be administered prior to, along with, or after administration,
e.g.,
application, infiltration and/car injection of the local anesthetic agent in
controlled
release form, in each case with a substantial prolongation of local anesthesia
in vivo.
The augmenting agent can be compounded in the same controlled release
formulation as a local anesthetic agent or agents, in a separate controlled
release
formulation, e.g., dii~'erent injectable microspheres, or in a non-controlled
release,
CA 02349017 2001-06-12
9
i.e, immediate release formulation. The augmenting agent may be administered
before, simultaneously with, or after injection or infiltration, implantation
or
insertion of the controlled release local anesthetic formulation at the
desired site.
In those embodinn ents of the invention directed to formulations where the
augmenting agent is included in the formulation with the local anesthetic, the
augmenting agent may be included in controlled release form or in immediate
release form. The augmenting agent may be incorporated into any
pharmaceutically
acceptable carrier and preferably a carrier providing controlled release,
including,
e.g., a controlled release matrix along with the local anesthetic;
incorporated into a
l0 controlled release coating on a controlled release device or formulation;
or
incorporated as an immediate release layer coating the local anesthetic
formulation.
On the other hand, the augmenting agent may be incorporated into a
pharmaceutically acceptable aqueous medium suitable for infiltration or
injection,
either in controlled release firm or in immediate release form.
Definitions
The controlled release formulations and methods of the invention may be
used in conjunction with any system for application, infiltration,
implantation,
insertion, or injection known in the art, including but not limited to
microparticles,
2~ e.g., microspheres or microcapsules, gels, pastes, implantable rods,
pellets, plates or
fibers, and the like (generically referred to as "substrates").
As used herein, the terms, "sustained release" and "controlled release" are
well understood in the art and are intended to be interchangeable.
As used herein, the terrr:= "local anesthetic agent" or "local anesthetic"
means any drug which pro~~~ide s local numbness anU'or analgesia. The term
also
includes, but is not limited to, any drug which, when locally administered,
e.g"
topically or by infiltration or injection, provides localized full or partial
inhibition of
sensory perception and/or motor function Under either definition, the
localized
condition so induced is also referred to herein as "local anesthesia". Local
CA 02349017 2001-06-12
anesthetic agents which can be used include, simply by way of example,
bupivacaine, ropivacaine, dibuc:aine, procaine, chloroprocaine, prilocaine,
mepivacaine, etidocaine, tetrac,aine, lidocaine, and xylacaine, as well as
anesthetically active derivatives, analogs and mixtures thereof. The local
anesthetic
5 can be in the form of a salt, fir example, the hydrochloride, bromide,
acetate,
citrate, carbonate or sulfate. I~lfore preferably, the local anesthetic agent
is in the
form of a free base. The free base provides a slower initial release and
avoids an
early "dumping" of the local anesthetic at the injection site. Preferred local
anesthetic agents include, e.g., bupivacaine. Local anesthetic agents
typically
10 administered systematically nnay also be used in those cases where the
means of
administration results only in a local effect, rather than systemic. The term
"local
anesthetic" may also encompass, pursuant to the definitions provided herein, a
drug
of a different class than those traditionally associated with local anesthetic
properties, including but not Limited to morphine, fentanyl, and agents which,
for
example, can provide regional blockade of nociceptive pathways (afferent
and/or
efferent).
As used herein, the term "patient" broadly refers to any anima! that is to be
treated with the compositions and by the methods herein disclosed. The
disclosed
local anesthetic dosage form can provide localized pain blockade to any
animal,
e.g., any vertebrate, which it is desired to so anesthetize. In particular,
the
disclosed methods and compositions will find use in veterinary practice and
animal
husbandry for, e.g., birds and mammals, wherever prolonged local anesthesia is
convenient or desirable. In a preferred embodiment, the term includes humans
in
need of or desiring prolonged local anesthesia.
t~tlbmentina Agents
Augmenting agents according to the invention are compositions or
compounds that prolong the duration of local anesthesia and/or enhance the
effectiveness of local anesthetic agents when delivered to the site of local
anesthetic
CA 02349017 2001-06-12
11
administration before, simultaneously with or after the local anesthetic is
administered. The augmenting agents are not glucocorticosteroid agents.
In one embodiment, the augmenting agents include an alkalinizing agent.
The alkalinizing augmenting agents used herein preferably raise the pH of the
medium in which the local anesthetic agents in controlled release form are
present
(e.g., either an injection medium or the environment at the site of injection)
to
provide a pH from about 5.0 to about 8.5, preferably from about 7.5 to about
8.5.
Preferably, the alkalinizing agent may be, for example, a carbonate buffer
such as
sodium carbonate. Of course, any other alkalinizing agent that is
pharmaceutically
acceptable for localized injection or infiltration may also be effectively
employed.
The augmenting agents also include non-glu:.ocorticoid steroids such as
e.g., androgens, such as testosterone and its active derivatives, analogs and
metabolites; estrogens, such. as estradiol and its active derivatives, analogs
and
metabolites and progestins, such as progesterone and its active derivatives,
analogs
and metabolites and mirtare~s of any of these.
In another embodiment, the augmenting agents are neuroactive steroids,
such as, e.g., one or more of the class of anesthetic steroids. Neuroactive
steroids
useful as augmenting agents according to the invention also include those
which
modulate GABA receptor's. Preferred neuroactive steroids include, simply by
way
of example, althesin and its main component, alphaxalone and active analogs,
derivatives and mixtures thereof, as well as 5-alpha-pregnane-3 alpha-21-diol-
20-
one (tetrahydro-deoxycorticosterone or THDOC) and/or allotetrahydrocortisone
(the 17-beta configuratiort); and dehydroepiandrosterone ("DHE") and active
analogs, derivatives and roi:~tures thereof. Preferably, the neuroactive
steroids are
present as an additive in the vehicle carrying the microspheres in a
concentration
ranging from about 0.01 to about 1 percent by weight, and most preferably from
abe:~t 0.05 to about 0.5 percent by weight.
The augmenting agents also include non-steroidal modulators of GABA
receptors, including those that are capable of potentiating the inhibitory
effects of
CA 02349017 2001-06-12
12
GABA on those receptors. Preferably, these include the benzodiapenes, e.g.,
diazepam as well as its active clerivatives, analogs and metabolites and
mixtures
thereof More preferably, t''#re diazepam is present as an additive in the
vehicle in a
concentration ranging from about 0.01 to about 1 percent by weight, and most
preferably from about 0.05 to .about 0.5 percent by weight. Of course, the
artisan
will appreciate that the potency of benzodiazapenes varies widely, and will
adjust
these concentration ranges accordingly for other benzoldiazapenes, relative to
the
potency of diazepam.
In yet another aspect of the invention, the augmenting agent is a modulator
to of ionic transport across cell membranes. Monovalent and multivalent metal
ion
transport can be modulated. Agents include, e.g., sodium, potassium and
calcium
channel modulators (e.g., nifedipine, nitrendipine, verapamil, etc.). In
preferred
embodiments, these also include, but are not limited to, aminopyridine,
benzamil,
diazoxide, 5,5 diphenylhydantoin, minoxidil, tetrethylammonium and valproic
acid.
Preferably, the ion transporr modulating agent is present as an additive in
the
vehicle carrying the microspheres in a concentration ranging from about 0.01
to
about 5 percent by weight, and most preferably from about 0.05 to about 1.5
percent by weight.
Augmenting agents also include, e.g., antipyretic agents such as
aminopyrine, phenazone, dipyrone, apazone, phenylbutazone and derivatives and
analogs thereof Aminopyrine is preferably included in the vehicle containing
the
microspheres in a concentration ranging from about 0.01 to about 0.5 percent
and
in a more preferred embodiment the concentration ranges from about 0.05 to
about
0.~ percent, by weight.
Other preferred augmenting agents include, e.g., adrenergic receptor
modulators, such as a2 receptor agonists, can also be used as augmenting
agents.
Simply by way of example. the a? receptor agonist clonidine provides useful
augmentation of local anesthesia, although any other art known a2 receptor
modulators capable of augmenting local anesthesia according to the invention
may
CA 02349017 2001-06-12
13
be used. Clonidine is preferably included in the vehicle containing the
microspheres
in a concentration ranging from about 0.01 to about 0.5 percent and in a more
preferred embodiment the concentration ranges from about 0.05 to about I.0
percent, by weight.
Tubulin binding agents that are capable of promoting the formation or
disruption of cytoplasmic microtubules are may be employed as augmenting
agents
according to the invention. Such agents include, for example, colchicine and
the
vinca alkaloids (vincristine and vinblastine) as well as active derivatives,
analogs
metabolites and mixtures thereof. Of course, some agents may be classified in
more
than one category, thus, for example, colchicine is also known to inhibit
glucose
metabolism in leukocytes. Colchicine is preferably included in the vehicle
containing the microspheres in a concemration ranging from about 0.01 to about
1.0 percent and in a mc>re~ preferred embodiment the concentration ranges from
about 0.05 to about 0. ~ percent, by weight
Osmotic polysaccharides are also able to be used as augmenting agents. In
a one preferred embodiment, the osmotic polysaccharide includes dextran. More
preferably, the dextran augmenting agents according to the invention have a
molecular weight ranging from 20 kDa through 200 kDa, or greater. A solution
containing dextran in a form suitable for injection or infiltration into a
desired site in
a patient is preferably buffered to a pH ranging from 3.0 to 8.5, but in a
preferred
aspect is buffered to a pH ranging from 7.0 to 8.5.
Other preferred embodiments of the invention provide for potassium-ATP
channel agonists for use as augmenting agents. A preferred potassium-ATP
channel
agonist is, e.g., diazoxide, as well as its active derivatives, analogs,
metabolites and
mixtures thereof are useful as augmenting agents
S~dium/potassiunn ATPase inhibitors are also preferred as augmenting
agents according to the invention. Preferably, the sodium/potassium ATPase
inhibitors are cardiac glycosides that are effective to augment local
anesthesia.
Cardiac glycosides than are useful according to the im~ention include, e.g.,
oubaine,
CA 02349017 2001-06-12
14
digoxin, digitoxin and active derivatives, analogs and metabolites and
mixtures of
any of these.
Additionally, augmenting agents according to the invention include, e.g.,
neurokinin antagonists, such as, e.g., spantide and other peptide inhibitors
of
substance P receptors that are well known to the art, e.g., as are listed in
Receptor
and Ion Channel Nomenclature Supplement, Trends in Pharmacological Sciences
18:64-65.
PLC inhibitors such as, e.g., 1-[6-[[17-beta-3-methoxyestra-1,3,5(10)-triene-
17-
yl]amino]hexl]-1-H-pyrrole-2,5-dione, and anti-seizure agents and agents that
stabilize cell membrane potential, such as, e.g., benzodiazepines,
barbiturates,
deoxybarbiturates, carbamazepine, succinamides, valproic acid,
oxazalidienbiones,
phenacemide and active derivatives, analogs and metabolites and mixtures
thereof.
Preferably, the anti-seizure augmenting agent is phenytoin, and most
preferably is
5,5-diphenylhydantoin.
Surprisingly, locally acting vasoconstrictive agents, also provide effective
augmentation of local anesthesia that is unexpectedly superior to that
provided by
immediate release vasoconstrictive agents. While not wishing to be bound by
any
hypothesis as to how vasconstrictive agents in sustained release form might
greatly
prolong local anesthetic activity, it is believed that sustained release
vasoconstrictor
agents provide a controlled and r~on-toxic vasoconstrictor activity that
reduces the
rate of local anesthetic washout fi-om the treated tissue area to prolong the
presence
of effective concentrations of local anesthetic in the tissue. It is known to
the art
that vasoconstrictors, e.g., epinephrine, prolong local anesthetic activity
for, at best,
about 1 hour and that if excessive amounts of epinephrine or other
vasoconstrictor
is administered in an attempt to further prolong local anesthesia, local
circulation
may be so disrupted as to cause tissue necrosis and gangrene.
Surprisingly, controlled release vasoconstrictor agents can achieve local
tissue concentrations that are safe and effective to provide vasoconstrictor
activity
effective to substantially prolong local anesthesia. Wore surprisingly, the
local
CA 02349017 2001-06-12
circulatory bed, i.e., blood vessels, remain responsive to the vasoconstrictor
agent
for prolonged periods, e.g., receptor desensitization or smooth muscle fatigue
or
tolerance does not prevent the prolongation effect. The gradual release from a
sustained release formulation also serves to greatly reduce the risk of toxic
5 reactions such as, e.g., localized tissue necroses
As for the previously discussed augmenting agents, vasoconstrictive
augmenting agents can be administered before, simultaneously with or after the
administration of local anesthetic. In one embodiment of the invention, at
least a
portion of the vasoconstrictive agent is formulated in a sustained release
10 formulation together with local anesthetic. In another embodiment, the
vasconstrictive agent is prepared in one or separate sustained release
formulations.
It will be appreciated that b:y manipulating the loading of, e.g.,
microspheres
containing vasoconstrictor agent, the artisan can determine the number of
microspheres necessary t~a administer a given dose. Thus, simply by way of
15 example, microspheres loaded with ahout 75 percent by weight of
vasoconstrictor
agent will require half of the microspheres necessary to administer a
predetermined
dose than will microspheres, loaded with about 45 percent by weight of
vasoconstrictor agent.
Vasoconstrictor agents can formulated into, e.g., sustained release
2 0 microspheres including both a local anesthetic, e.g., bupivacaine free
base, and a
vasoconstrictor agent. Vasoconstrictor agents can also be formulated into,
e.g.,
sustained release microspheres including local anesthetic without a
vasoconstrictive
agent.
In one embodiment. local anesthetic and vasoconstrictor agents are
administered simultaneously in the form of, e.g., separate microspheres
suspended
in a single medium suital}le for injection or infiltration, or in separate
microspheres
suitable for injection, e.g., at the same site. In a further embodiment,
simply by way
of example, administration of sustained release microspheres with combined
local
anesthetic and vasoconstrictor agent can also be followed by one or more
additional
CA 02349017 2001-06-12
16
administrations of such combination formulation and/or of microspheres
including
as the active agent only local anesthetic or only vasoconstrictor agent.
Augmenting agents that are vasoconstrictor agents in sustained release form
include, but are not limited to., catecholamines e.g., epinephrine,
norepinephrine
and dopamine as well as, e.g., metaraminol, phenylephrine, methoxamine,
mephentermine, methysergide, ergotamine, ergotoxine, dihydroergotamine,
sumatriptan and analogs, and alpha-1 and alpha-2 adrenergic agonists, such as,
e.g.,
clonidine, guanfacine, guanaben:: and dopa (i.e., dihyrdoxyphenylalanine),
methyldopa, ephedrine, amphetamine, methamphetamine, methylphenidate,
to ethylnorepinephrine ritalin, peenoline and other sympathomimetic agents,
including active metabolites, derivatives and mixtures of any of the
foregoing.
In a more preferred embodiment, at least a portion of any of the augmenting
agents enumerated above are included in the controlled release formulation, in
combination with a local anesthetic agent or agents in a concentration ranging
from
about 0.01 to about 30 percent or more, by weight, relative to the weight
ofthe
formulation.
The artisan will also appreciate that other augmenting agents according to
the invention broadly include any other types and classifications of drugs or
active
agents known to the art. Such augmenting agents are readily identified by
routine
2o screening as discussed hereinbelow using animal sensory and motor
quantitation
protocols well known to the art.
A local anesthetic according to the invention can also be formulated, e.g., in
injectable microspheres, in combination with at least one vasoconstrictor
augmenting agent according to the invention. In one embodiment, the
2 5 vasoconstrictor can be included in the vehicle suitable far injection
carrying the
microspheres. In a further embodiment, at least a portion of the
vasoconstrictor can
also be formulated into a sustainf:d release formulation, e.g., injectable
microspheres, together with the local anesthetic. In a still further
embodiment, at
CA 02349017 2001-06-12
17
least a portion of the vasoconstrictor can be prepared in a separate sustained
release
formulation.
The vasoconstrictcar can be included in either a single or combination
formulation in an amount ranging from about 0.001 percent to about 90 percent,
by
weight relative to the total weight of the formulation. Preferably, the
vasoconstrictor is included in a controlled release formulation in an amount
ranging
from about 0.005 percent to about 20%, and more preferably, from about 0.05
percent to about 5 percent, by weight, relative to the total weight of the
formulation. When a vasoconstrictor is present in the injection vehicle in
immediate
release form, it is present in amounts ranging from about 0 01% to about 5
percent,
or more, by weight, relative to the injection vehicle. The vasoconstrictor can
also
be provided in a ratio of local anesthetic, e.g., bupivacaine to
vasoconstrictor,
ranging from about 10:1 to about 20,000 and preferably from about 100:1 to
about
2000:1 and from about 500: ( to about 1500:1.
Of course, the artisan will appreciate that the amounts of augmenting agent
and local anesthetic will vary depending upon the relative potency of the
agents
selected, the depth and duration of local anesthesia desired.
Of course, the artisan will appreciate that the optimal concentration and/or
quantities or amounts of ar~y particular augmenting agent, whether present in
the
injection vehicle, separately administered before, during or after local
anesthesia is
induced or whether included in the microsphere formulation, may be adjusted to
accommodate variations in the treatment parameters. Such treatment parameters
include the polymer composition of a particular microsphere preparation, the
particular local anesthetic utilized, and the clinical use to which the
preparation is
put, in terms of the site treated for local anesthesia, the type of patient,
e.g., human
or non-human, adult or child, and the type of sensory stimulus to be
anesthetized.
Further, the concentration and/or amount of any particular augmenting
agent for a given formulation may readily identiFed by routine screening in
animals,
e.g, rats, by screening a range of concentration and/or amounts of augmenting
agent
CA 02349017 2001-06-12
18
using the hotplate foot withdrawal assay and/or motor function assay described
hereinbelow. Art known meahods are also available to assay local tissue
concentrations, diffusion rates from microspheres and local blood flow before
and
after administration of local anesthetic formulations according to the
invention.
One such method is microdialysis, as reviewed by T.E. Robinson et al., 1991,
MICRODIALYSIS IN THE NEUROSCIENCES, Techniques, volume 7, Chapter
1, pages I-64. The methods reviewed by Robinson can be applied, in brief, as
follows. A microdialysis looF~ is placed in situ in a test animal. Dialysis
fluid is
pumped through the loop. When microspheres according to the invention are
to injected adjacent to the loon, released drugs, e.g., bupivacaine and
vasoconstrictor
augmenting agents, are collected in the dialysate in proportion to their local
tissue
concentrations. The progress of diffusion of the active agents can be
determined
thereby with suitable calibration procedures using known concentrations of
active
agents. For the vasoconstrictor augmenting agents, decrements and durations of
vasoconstriction effects can bc: measured by clearance rates of marker
substances,
e.g., methylene blue or radialabeled albumen from the local tissue. from the
microspheres, as well as the local blood flow
The optimal concentration of augmenting agent for human clinical use may
also be readily determined by routine animal screening as described
hereinbelow,
2 0 and further adjusted, where indicated, by routine clinical experience.
Formulations
Any pharmaceutically acceptable carrier vehicle or formulation suitable for
local implantation, infiltration or injection in proximity to a nerve that is
able to
2 5 provide a controlled release of a local anesthetic agent and/or augmenting
agent
may be employed to provide for prolonged local anesthesia as needed. Slow
release
formulations known in the art include specially coated pellets, polymer
formulations
or matrices for surgical insertion or as controlled release microparticles,
e.g.,
microspheres or microcapsules, for implantation, insertion or injection,
wherein the
CA 02349017 2001-06-12
19
slow release of the active medicament is brought about through controlled
diffusion
out of the matrix and/or selective breakdown of the coating of the preparation
or
selective breakdown of a polymer matrix. Other formulations or vehicles for
controlled or immediate delivery of an agent to a preferred localized site in
a patient
include, e.g., suspensians, emulsions, liposomes and any other suitable, art
known,
delivery vehicle or formulation.
In a preferred embodiment, the slow release formulation is prepared as
microspheres in a size distril'~ution range suitable for local infiltration or
injection.
The diameter and shape of the microspheres or other particles can be
manipulated
to modify the release characteristics. For example, larger diameter
microspheres
will typically provide slower rates of release and reduced tissue penetration
and
smaller diameters of microspheres will produce the opposite effects, relative
to
microspheres of different mean diameter but of the same composition. In
addition,
other particle shapes, such as, for example, cylindrical shapes, can also
modify
release rates by virtue of the increased ratio of surface area to mass
inherent to such
alternative geometrical shapes, relative to a spherical shape. The diameter of
injectable microspheres are in a size range from, for example, from about 5
microns
to about 200 microns in diameter. In a more preferred embodiment, the
microspheres range in diarneter from about 20 to about 120 microns.
2 0 A wide variety of biodegradable materials may be utilized to provide the
controlled release of the local anesthetic. Any pharmaceutically acceptable
biodegradable polymers known to those skilled in the art may be utilized. It
is
preferred that the biodegradable controlled release material degrade in oivo
over a
period of less than about tv.~,~o years, with at least 50°,'° of
the controlled release
material degrading within about one year, and more preferably six months or
less.
More preferably, the controlled release material will degrade significantly
within one
to three months, with at least 50% of the material degrading into non-tonic
residues
which are removed by the body, and 100% of the drug being released within a
time
period from about two weeks to about two months. The controlled release
material
CA 02349017 2001-06-12
should preferably degrade by hydrolysis, and most preferably by surface
erosion,
rather than by bulk erosion, so that release is not only sustained but also
provides
desirable release rates. However, the pharmacokinetic release profile of these
formulations may be first order, zero order, bi- or multi-phasic, to provide
the
5 desired reversible local anesthetic effect over the desired time period.
The controlled release material should be biocompatible. In the case of
polymeric materials, biocompatibility is enhanced by recrystallization of
either the
monomers forming the polymer and/or the polymer using standard techniques.
Suitable biodegradable; polymers can be utilized as the controlled release
10 material. The polymeric material may comprise a ~olylactide, a
polyglycolide, a
poly(lactide-co-giycolide), a polyanhydride, a polyorthoester,
polycaprolactones,
polyphosphazenes, polysaccharides, proteinaceous polymers, soluble derivatives
of
polysaccharides, soluble derivatives of proteinaceous polymers, polypeptides,
polyesters, and polyorthoesters or mixtures or blends of any of these. The
15 polysaccharides may be poly-1,4-glucans, e.g., starch glycogen, amylose,
amylopectin, and mixtures thereof The biodegradable hydrophilic or hydrophobic
polymer may be a water-soluble derivative of a poly-1,4-glucan, including
hydrolyzed amylopectin, hydroxyalkyl derivatives of hydrolyzed amylopectin
such
as hydroxyethyl starch (HES), hydroxyethyl amylose, dialdehyde starch, and the
20 like. Preferred controlled release materials which are useful in the
formulations of
the invention include the polyanhydrides, co-polymers of lactic acid and
glycoIic
acid wherein the weight ratio of lactic acid to glycolic acid is no more than
4:1 (i.e.,
80% or less lactic acid to 20° o or more glycolic acid by weight), and
polyorthoesters containing a catalyst or degradation enhancing compound, for
2 5 example, containing at least 1 °/~ by weight anhydride catalyst
such as malefic
anhydride. Other useful polymers include protein polymers such as gelatin and
fibrin and polysaccharides such as hyaluronic acid. Since potylactic acid
takes at
least one year to degrade iar viao, this polymer should be utilized by itself
only in
circumstances where such a degradation rate is desirable or acceptable.
CA 02349017 2001-06-12
21
The polymeric material may be prepared by any method known to those
skilled in the art. For example, where the polymeric material is comprised of
a
copolymer of lactic and glycolic acid, this copolymer may be prepared by the
procedure set forth in U.S. Patent No. 4,293,539 (Ludwig, et al.).
In brief, Ludwig prepau-es
such copolymers by condensation of lactic acid and glycolic acid in the
presence of
a readily remoTMble polymerization catalyst (e.g., a strong acid ion-exchange
resin
such as Dowex HCR-W2-:EI). The amount of catalyst is not critical to the
polymerization, but typically is from about 0.01 to about 20 parts by weight
relative
to the total weight of combined lactic acid and glycolic acid. The
polymerization
reaction may be conducted without solvents at a temperature from about
I00° C to
about 250° C for about 48 to about 96 hours, preferably under a reduced
pressure
to facilitate removal of water and by-products. The copolymer is then
recovered by
filtering the molten reaction mixture to remove substantially all of the
catalyst, or by
cooling and then dissolving the reaction mixture in aF~ organic solvent such
as
dichloromethane or acetcme; and then filtering to remove the catalyst.
Pharmaceutically acceptable polyanhydrides which are useful in the present
invention have a water-labile anhydride linkage. The rate of drug release can
be
controlled by the particular polyanhydride polymer utilized and its molecular
weight. The polyanhydride polymer may be branched or linear. Examples of
polymers which are useful in the present invention include homopolymers and
copolymers of poly(lactic acid) and/or poly(glycolic acid), poly[bis(p-
carboxyphenoxy)propane anhydride] (PCPP), poly[bis(p-carboxy)methane
anhydride] (PCPM), polyanhydrides of oligomerized unsaturated aliphatic acids,
polvanhydride polymers prepared from amino acids which are modified to include
an additional carboxylic acid, aromatic polyanhydride compositions, and co-
polymers of polyanhydrides w-itfi other substances, such as fatty acid
terminated
polyanhydrides, e.g., polyanhydrides polymerized from monomers of dimers
and/or
trimers of unsaturated fatty acids or unsaturated aliphatic acids
folyanhydrides
CA 02349017 2001-06-12
22
may be prepared in accordance with the methods set forth in U.S. Patent No.
4,757,128. For example, polyanhydrides may be
synthesized by melt polycondensation of highly pure dicarboxylic acid monomers
converted to the mixed anhydride by reflux in acetic anhydride, isolation and
purification of the isolated prepolymers by recrystallization, and melt
polymerization
under low pressure ( 10'~ mm ) with a dry ice/acetone trap at a temperature
between
140°-250° C. for 10-300 minutes. High molecular weight
polyanhydrides are
obtained by inclusion of a catalyst which increases the rate of anhydride
interchain
exchange, for example, alkaline earth metal oxides such as CaO, Ba0 and CaC03.
Polyorthoester polymers may bf: prepared, e.g., as set forth in U.S. Patent
No.
4,070,347.
Proteinaceous polymers may also be used Proteinaceous polymers and
their soluble derivatives include gelation biodegradable synthetic
polypeptides,
elastin, alkylated collagen, alk:yl;ated elastin, and the like. Biodegradable
synthetic
polypeptides include poly-(N-.hydroxyalkyl)-L-asparagine, poly-(N-
hydroxyalkyl)-
L-glutamine, copolymers of Ti-hydroxyalkyl-L-asparagine and N-hydroxyallyl-L-
glutamine with other amino acids. Suggested amino acids include L-alamine, L-
lysine, L-phenylalanine, L-valine~, L-tyrosine, and the like.
In embodiments whert~ the biodegradable polymer comprises a gel, one such
useful polymer is a thermally gel',ling polymer, e.g., polyethylene oxide,
polypropylene oxide (PEO-PPO) block copolymer such as Pluronic~ F127 from
BASF Wyandotte. In such cases, the local anesthetic formulation may be
injected
via syringe as a free-flowing liquid, which gels rapidly above 30°C
(e.g., when
injected into a patient) The gel system then releases a steady dose of local
anesthetic at the site of administration.
In additional embodiments, the controlled release material, which iri effect
acts as a carrier for the local anesthetic and/or the augmenting agent, can
further
include a bioadhesive polymer such as pectins (polygalacturonic acid),
CA 02349017 2001-06-12
23
mucopolysaccharides (hy~aluronic acid, mucin) or non-toxic lectins or the
polymer
itself may be bioadhesive, e. g., polyanhydride or polysaccharides such as
chitosan.
Definitions or fiarther descriptions of any of the foregoing terminology are
well known in the art and may be found by referring to any standard
biochemistry
reference text such as "Biochemistry" by Albert L. Lehninger, Worth
Publishers,
Inc, and "Biochemistry" by Lubert Stryer, W.H. Freeman and Company.
The aforementionf:d biodegradable hydrophobic and hydrophilic polymers
are particularly suited fc:~r the methods and compositions of the present
invention by
reason of their characteristically low human toxicity and virtually complete
biodegradability.
The substrates of the presently described formulations in certain preferred
embodiments are manufactured using a method that evenly disperses the local
anesthetic throughout the forn~ulation, such as emulsion preparation, solvent
casting, spray drying or hot melt, rather than a method such as compression
molding. A desired release profile can be achieved by using a mixture of
polymers
having different release rages and/or different percent loading of local
anesthetic
and/or augmenting agent, for example, polymers releasing in one day, three
days,
and one week. In addition, a mixture of microspheres having one or more
different
local anesthetic agents, haring the same or different controlled release
profile, can
be utilized to provide the benefits of different potencies and spectrum of
activity
during the course of treatment.
Methods for manufacture of microspheres are well known and are typified in
the following examples. Examples of suitable methods of making microspheres
include solvent evaporation, phase separation and fluidized bed coating.
In solvent evaporation procedures, the local anesthetic agent, if soluble in
organic solvents, may be entrapped in the biodegradable polymer by dissolving
the
polymer in a volatile organic solvent, adding the dn.ig to the organic phase,
emulsifying the organic phase in water which contains less than 2% polwinyl
CA 02349017 2001-06-12
24
alcohol, and finally removinc; tlhe solvent under vacuum to form discrete,
hardened
monolithic microspheres.
Phase separation micro.°ncapsulation procedures are suitable for
entrapping
water-soluble agents in the polsrmer to prepare microcapsules and
microspheres.
Phase separation involves coacervation of the polymer from an organic solvent
by
addition of a nonsolvent such as silicone oil. In a preferred embodiment, the
microspheres may be prepared by the process of Ramstack et al., 1995, in
published international patent application Wp 95/13799.
The Ramstack et al. process essentially provides
for a first phase, including an active agent and a polymer, and a second
phase, that
are pumped through a static mixer into a quench liquid to form microparticles
containing the active agent. T'he first and second phases can optionally be
substantially immiscible and the second phase is preferably free from solvents
for
the polymer and the active agent and includes an aqueous solution of an
emulsifier.
In fluidized bed coatinc;, the drug is dissolved in an organic solvent along
with the polymer. The solution is then processed, e.g., through a Wurster air
suspension coating apparatus to form the final microcapsule product.
The biodegradable controlled release materials may be used in order to
prepare controlled release local anesthetic implants. The implants may be
manufactured, e.g., by compression molding, injection molding, and screw
extrusion, whereby the Local anesthetic agent is loaded into the polymer.
Implantable fibers can be manufactured, e.g., by blending the local anesthetic
agent
with the controlled release material and then extrudins the mixture, e.g.,
under
pressure, to thereby obtain biodegradable fibers. In certain preferred
embodiments,
the augmenting agent may be incorporated into the implant, or may be coated
onto
a surface of the implant.
In other embodiments of'th,e invention, the controlled release material
comprises an artificial lipid vesicle, or liposome. The use of liposomes as
drug
delivery systems is known, and c:ornprehensive review articles on their
properties
CA 02349017 2001-06-12
and clinical applications are available; see, e.g., Barenholz and Amselem, in
"Liposome Technoloev", end ed., G. Gregoriadis, ed., CRC Press, 1992;
Lichtenberg and Barenholz, in Methods for Biochemical Anal sis, 33, D. Glick,
ed.,
1988. A liposome is defined as a structure consisting of one or more
concentric
lipid bilayers separated by water or aqueous buffer compartments. These hollow
structures, which have an internal aqueous compartment, can be prepared with
diameters ranging from 20 nrn to 10 pm. They are classified according to their
final
size and preparation method as: SUV, small unilamellar vesicles (0.5-50 nm);
LUV,
large unilamellar vesicles ( 100 nm); REV, reverse phase evaporation vesicles
(0.5
um); and MLV, large multila:mellar vesicles (2-10 um).
Liposomes as described herein will vary in size. Preferably, the liposomes
have a diameter between I ~:i0 nrn and I 0 microns or greater. A wide variety
of lipid
materials may be used to form the liposomes including natural lecithins, e.g.,
those
derived from egg and soya bean, and synthetic lecithins, the proviso being
that it is
preferred that the lipids are non-immunogenic and bio-degradable. Also, fipid-
based materials formed in combination with polymers may be used, such as those
described in U.S. Patent No. .'i,188,837 to Domb.
Examples of synthetic lecithins which may be used together with their
respective phase transition temperatures, are di-
(tetradecanoy)phosphatidylcholine
(DTPC) (23 ° C), di-(hexadecanoyl)phosphatidylcholine (DHPC) (41
° C) and di-
(octandecanoyl) phosphatidylc:holine (DOPC) (SS ° C). Di-(hexadecanoyl)
phosphatidylcholine is preferred as the sole or major lecithin, optionally
together
with a minor proportion of the di-{octadecanoyl) or the di-(tetradecanoyl)
compound. Other synthetic lecithins which may be used are unsaturated
synthetic
lecithins, for example, di-(oleyl)phosphatidyl-choline and di-
(linoleyl)phosphatidyicholine. In addition to the main liposome-forming lipid
or
lipids, which are usually phospholipids, other lipids (e.g. in a proportion of
S-40%
w/w of the total lipids) may be included, for example, cholesterol or
cholesterol
CA 02349017 2001-06-12
26
stearate, to modify the structure of the liposome membrane, rendering it more
fluid
or more rigid depending on the nature of the main liposome-forming lipid or Ii
ids.
P
In certain embodiments, the augmenting agent is incorporated alon with
g
the local anesthetic agent into the lipid. In other preferred formulations the
li '
pads
containing the local anesthetic agent are dispersed in a pharmaceutically acce
tabl
P a
aqueous medium. The augmenting agent may be incorporated into this aqueous
medium. In a further embodiment, a portion of the dose of the local anesthetic
i
s
incorporated into the aqueous medium in immediate release form. The result
ant
formulation is an aqueous suspension which may comprise the local anestheti
c
and/or augmenting agent partitioned between a free aqueous phase and a li oso
phase. p me
As an even further alternate embodiment, liposomes containing local
anesthetic may be combined in an aqueous phase where liposomes containin the
g
augmenting agent to form an aqueous pharmaceutical suspension useful for
administration at the desired site in the patient to be anesthetized. This ma
be
Y
accomplished via injection or implantation. Liposomes may be prepared by
dissolving an appropriate amount of a phospholipid or mixture or phos holi ids
_
P P
together with any other desired Lipid soluble components (e.g., cholesterol,
cholesterol stearate) flowing in a suitable solvent (e.g., ethanol) and eva
oratin
P g to
dryness. An aqueous solution of the local anesthetic, optionally with au
mentin
g g
agent, may then be added and rni~;ed until a lipid film is dispersed. The
resulting
suspension will contain Iiposomes ranging in size, which may then fractionated
to
remove undesirable sizes, if necessary. This fractionation may be effected by
column gel chromatography, centrilueation, ultracentrifugation or by dialysis,
as
well known in the art.
The above method of preparation of liposomes is representative of a
possible procedure only. Those skilled' in the art will appreciate that there
are man
Y
different methods of preparing liposomes, all of which are deemed to be
encompassed by the present disclosure.
CA 02349017 2001-06-12
27
In additional embodiments of the invention, the substrate comprises a
plurality of microcapsules laden with the local anesthetic agent with or
without the
augmenting agent. Microc:apsules may be prepared, for example, by dissolving
or
dispersing the local anesthetic agent in an organic solvent and dissolving a
wall
forming material (polystyrene, alkylcelluloses, polyesters, polysaccharides,
polycarbonates, poly(meth)acrylic acid ester, cellulose acetate,
hydroxypropylmethylcellulose phthalate, dibutylaminohydroxypropyl ether,
polyvinyl butyral, polyvinyl formal, polyvinylacetal-diethylamino acetate, 2-
methyl-
S-vinyl pyridine methacrylate-methacrylic acid copolymer, polypropylene,
vinylchloride-vinylacetate copolymer, glycerol distearate, etc.) in the
solvent; then
dispersing the solvent containing the local anesthetic agent and wall forming
material in a continuous-phase processing medium, and then evaporating a
portion
of the solvent to obtain microcapsules containing the local anesthetic agent
in
suspension, and finally, extracting the remainder of the solvent from the
microcapsules. This procedure is described in more detail in U.S. Patent Nos.
4,389,330 and 4,530,84().
The controlled release dosage forms of the present invention preferably
provide a sustained actie~n i.n the localized area to be treated. For example,
it would
be desirable that such a formulation provides localized anesthesia to the site
for a
period of one day, two days, three days, or longer. The formulations can
therefore,
of course, be modified in order to obtain such a desired result.
Microspheres and other injectable substrates described herein may be
incorporating an effective amount of the same into a pharmaceutically
acceptable
solution (e.g., water) or ::suspension for injection. The final reconstituted
product
viscosity may be in a range suitable for the route of administration. In
certain
instances, the final reconstituted product viscosity may be, e.g., about 3~
cps.
Administration may be vi.a the subcutaneous or intramuscular route. However,
al-
ternative routes are also contemplated, and the formulations may be applied to
the
localized site in any manner known to those skilled in the art, such that a
localized
CA 02349017 2001-06-12
2a
effect is obtained. The substrata formulations of the invention can be
implanted at
the site to be treated. Thereby, the formulations of the present invention,
when
including a local anesthetic, may be used in the control of post-operative
pain.
The local anesthetic is incorporated into the polymer or other controlled-
release formulation in a percent loading between 0.1% and 90% or more, by
weight, preferably between 5~'0 .and 80%, or more, by weight and more
preferably
between 65 and 80%, or more:, by weight. In an even more preferred embodiment,
the local anesthetic is loaded at about 75% by weight.
It is possible to tailor a system to deliver a specified loading and
subsequent
maintenance dose by manipulating the percent drug incorporated in the polymer
and
the shape of the matrix or fomulation, in addition to the form of local
anesthetic
(e.g., free base versus salt) and the method of production. The amount of drug
released per day increases proportionately with the percentage of drug
incorporated
into the formulation, e.g., matrix: (tor example, from 5 to 10 to 20%). In the
preferred embodiment, polymer matrices or other formulations with about 75%
drug incorporated are utilized, although it is possible to incorporate
substantially
more drug, depending on the dnig, the method used for making and loading the
device, and the polymer.
When the augmenting agent is included in the controlled release substrates
comprising local anesthetic, it has been found that useful loadings of
augmenting
agent are from about 0.001% to about 30% by weight of the substrate or
preferably
from about 0.01% to about 5% by weight of the substrate. When the augmenting
agent is included in controlled release substrates without local anesthetic,
it has
been found that useful loadings of augmenting agent are from about 0.001
percent
to about 90%, or more, by weight of the substrate, or preferably from about
0.001
to about 30% by weight of the substrate or more preferably from about 0.01% to
about 5% by weight of the substrate.
CA 02349017 2001-06-12
29
When the augmenting agent is included as part of the (aqueous) injection
medium, the augmenting agent may be present in a weight percent relative to
the
local anesthetic varying from about 0.01% to about 15%.
The dosage of thc; controlled release microsphere formulations is dependent
upon the kind and amount of the drug to be administered, the recipient animal,
and
the objectives of the treatment. For example, when the local anesthetic
included in
the microspheres of the present invention is bupivacaine, the formulation may
include, e.g., from about t)._'i to about 2 mg/kg body weight. The effective
dose of
bupivacaine, or an amount of another local anesthetic sufficient to provide
proportional potency, care range from about I to 50 mg of bupivacaine injected
or
inserted at each site where the release of a local anesthetic agent is
desired. In
certain preferred embodiments, the dose of bupivacaine in the controlled
release
dosage form of the invention is sufficient to provide a controlled release of
about 1
to 4 mg per day at the release site for at least 1 to 4 days. Since the
formulations of
the present invention are controlled release, it is contemplated that
formulations
may include much more than usual immediate release doses, e.g., as much as 120
mg/kg bupivacaine or more.
In certain preferred embodiments, the controlled release substrate
comprising local anesthetic and/or augmenting agent provides from about 10 to
2 o about 60 percent release of drug, e.g., local anesthetic after 24 hours,
from about
to about 80 percent release after 48 hours and from about 40 to about 100
percent release after 72 hours. More preferably, the controlled release
substrate
comprising local anesthetic pravides from about 2S to about 40 percent release
of
local anesthetic after 24 hc:>urs, from about 40 to about SO percent release
after 24
hours and from about 4S to about SS percent release after 72 hours and 80 to
100
percent cumulative release is provided after a;~out 280 hours.
In order to obtain a local anesthetic effect iu aiao when combined with the
augmenting agent as described herein of at least about 40 hours the augmenting
agent is placed into appro~,:imately the same site in a patient (e.g., human
or
CA 02349017 2001-06-12
veterinary) before, simultaneously with, or after the placement of a local
anesthetic
at that site. The presence of augmenting agent in the controlled release
formulation
does not significantly affect the in vitro release rates of local anesthetic.
In a preferred embodiment the local anesthetic effect is prolonged by the use
of an augmenting agent by at least about 15%, e.g., from about I S% to about
1400% or more preferably from about 300% to about 1000 percent or more and
more preferably from about 300% to about 500%, or more of the duration of the
local anesthetic effect that is obtained from the same formulation without
benefit of
an augmenting agent. The duration of the local anesthetic effect prolonged by
an
to augmenting agent ranges from about 30 minutes to about 150 hours, or more,
and
preferably from 1 hour to about 1 to about 24 hours or more, and more
preferably
from about 1 hour to about 1'? hours, or more.
The rate of release of local anesthetic agent or other drugs incorporated into
the formulation will also depend on the solubility properties of the local
anesthetic
15 or drug. The greater the solubility in water, the more rapid the rate of
release in
tissue, all other parameters bc:in;5 unchanged. For example, those local
anesthetic
agents having pH dependent solubility will be released more rapidly at the
optimum
pH for those compounds. Thus, the formulation may be optimized for the desired
local anesthetic release rate b:~ selecting local anesthetic agents having a
desired
2o water solubility in tissue, e.g., at: tissue pH. Thus, a local anesthetic
agent that is
more soluble at acid pH will have a faster release rate in a relatively acidic
(e.g., pH
less than about 7.2) tissue. For example, in one embodiment, the formulation
will
have released, iir vitro, at least TO percent of a local anesthetic at 48
hours at about
pH 6 and will have released at least 40 percent of a local anesthetic at a pH
ranging
25 from about 7.4 to about 8, at 48 hours. Other combinations are pH
independent in
their release.
The examples demonstrate that the above-described augmenting agents
prolong the duration of local anesthesia iu vioo and do not significantly
alter the
time course of release of bupivacaine in vitro.
CA 02349017 2001-06-12
31
Applications
Potential applications include any condition for which localized nerve
blockade is desirable. This includes both local anesthesia for the relief of
pain and
motor symptoms as well as local anesthesia for other medical purposes. The
formulations and methods according to the invention can be used to provide two
to
five day intercostal blockade: for thoracotomy, or longer term intercostal
blockade
for thoracic post-therapeutic: neuralgia, lumbar sympathetic blockade for
reflex
sympathetic dystrophy, or three-day ilioinguinaUiliohypogastric blockade for
hernia
repair. Other potential applications include obstetrical or gynecological
procedures.
to Yet further potential applications include providing localized temporary
sympathectomy, e.g., bloc:ka.de of sympathetic or parasympathetic ganglia to
treat a
variety of autonomic diseases, including circulatory dysfunction or cardiac
dysrhythmias. The formulations may also be used to treat trigeminal neuralgia
and
other diseases of the cranial nerves as well as to provide a temporary nerve
block to
treat localized muscle spasm and treatment of retrobulbar conditions, e.g.,
eye pain.
Other uses include intra-operative administration in order to reduce pain
during and
after the operative procedure, especially for plastic surgery procedures where
prolonged local anesthesia will enhance the outcome. These systems can also be
used for the management of various forms of persistent pain, such as
postoperative
2 o pain, sympathetically maintained pain, or certain forms of chronic pain
such as the
pain associated with many types of cancer. These systems may also be used for
blockade of nociceptive pathways (afferent and efferent) in patients with
acute
pancreatitis, ileus, or other visceral disorders. These are merely examples,
and
additional uses for both human and veterinary practice are immediately
apparent to
2 5 the artisan.
Methods of Administration
In a preferred method of administration a dosage form, e.g., microspheres,
are administered by injectic7n into a site where local anesthetic agent is to
be
CA 02349017 2001-06-12
32
released. Microspheres may be injected through a syringe or a trochar. Pellets
or
slabs may be surgically placed into a site where release of oral anesthetic
agent is
desired. Controlled release gels, pastes or suspensions, including gels,
pastes or
suspension containing microspheres, may also be administered topically to a
skin or
mucosal surface of the body to obtain topical, localized anesthesia.
As described below, micraspheres according to the invention can be
administered alone or in combination with a solution including a non-
glucocorticosteroid augmenting agent in an amount effective to prolong the
duration of local anesthesia. f~lternatively, the microspheres include an
amount of a
to non-glucocorticosteroid au~;m.ent agent effective to prolong the duration
of local
anesthesia.
In another alternative, one or more augmenting agents can be administered
before, simultaneously with or after administration of the controlled release
local
anesthetic, wherein the augmenting agent is formulated into a separate
microsphere
formulation for controlled release. The controlled release rate for the
augmenting
agents may be the same as c:rr different than the controlled release rate for
the local
anesthetic. The separate microsphere can be administered in a single
injection, i.e.,
in a single injection vehicle, or in separate injections simultaneously or at
dif~'erent
times In a further embodiment, it has been found that additional dose of
augmenting
agent may also be administered as an injectable solution, in an injectable
carrier or
in a controlled release carri~;r to the nerve to be blockaded after the
controlled
release local anesthesia has worn off, in order to reactivate the initial
local
anesthesia without the co-administration of additional local anesthetic.
The microspheres may be prepared from PLGA polymers ranging from, for
example, PLGA in a ratio of :~OI50, 65/35 or 75/25. An optimum composition has
been determined to be PLEA 65/35. The microspheres, formulated with, e.g.,
PLGA 65/35 microspheres are administered in a dose ranging from, for example,
2
through 450 mg of microspheres 7~% (w/w) loaded with a local anesthetic such
as
bupivacaine, per kg of the patient to be treated. In a preferred embodiment
the
CA 02349017 2001-06-12
33
dose ranges from 5 through 450 mg/kg. In a more preferred embodiment the dose
ranges from about 10 to about 150 mg/kg with PLGA 65/35. Certainly, the
artisan
will appreciate the fact that the dose ranges mentioned above are based on the
potency of bupivacaine, and that exact effective dosages will vary with the
particular relative potency ;and pharmacokinetics of each local anesthetic and
will be
able to readily adjust the do>se according to the degree of blockade
experienced by
the patient.
The use of the above-described augmenting agents before, simultaneously
with or after administration of a controlled release local anesthesia, results
in
prolonged anesthesia.
The formulation described herein can also be used to administer local
anesthetic agents that produce modality-specific blockade, as reported by
Schneider, et al., Anes~l~, 74:270-281 ( 1991 ), or that possess physical-
chemical attributes that make them more useful for sustained release then for
single
injection blockade, as reported by Masters, et al., Soc. Neurosci. Abstr.,
18:200
( 1992).
N OF
The following non-limiting examples illustrate the preparation of the. ,
formulations according to the invention and the effects of local anesthetic
and
augmenting agents alone and in combination.
EXA1~1PLES I-3 ~(SOLVEh'T Fwrr~e CZ-jON PR(lr~cc~
-__
In Examples 1-3, bupivacaine microspheres are prepared by dissolving the
bupivacaine base and the polymer in ethyl acetate. The polymer is 50:50 poly
(D,L)
lactic co-glycolic acid which has a mole percent composition of 50% lactide
and
50% glycolide. This dispersef phase is then added to a solution of polyvinyl
alcohol (PVA) in water (the continuous phase) with stirring. The resulting
emulsion is monitored for droplet size, which is in turn controlled by the
rate of
CA 02349017 2001-06-12
34
stimng. The emulsion is then added to water to extract the solvent and to
harden
the microspheres. The mixture is then filtered and the microspheres are dried
under
vacuum at room temperature. The desired particle size fraction is then
collected by
sieving.
Each of Examples I-.3 are prepared such that the microspheres have a
relatively high drug content. In Example 1, the theoretical drug content is
about
60%, and the size of the microspheres range from about 45 to about 90 microns.
In
Example 2, the theoretical druc; content is about 61 %, and the range in the
size of
the microspheres is from about 4~ to about 63 microns. In Example 3, the
theoretical drug content is about 65%, and the range in particle size of the
microspheres is from about 4.5 to about 63 microns.
The microspheres ofExarnples 1-3 are then suspended in a suitable media
for injection, in this case watf;r. Thereafter, the microspheres are subjected
to in-
vitro dissolution testing. An automated dissolution test method is utilized
using the
USP/NF Paddle Method II. ~'he dissolution medium is 900 ml of Tris buffer with
0.05% sodium dodecyl sulfate at plI 7.4 at 37° C with a stirring speed
of about 50
RPM. The surfactant is added in order to prevent the microspheres from
floating _
on the surface of the dissolution medium. Further information concerning these
formulations is presented in Table I below.
TABLE 1
FormulationM-Sphere TheoreticalActual MW of In vitro
Size % Drug % Drub 50:50 Release
Range _ dl-PLGA
. 24 ~s
72
hrs
Ex. I 45-9p~t 6~~~ ___ 47~o I _- 28% 68%
,
Ex.2 45-63~r 61'%--- 56% SOK 52% 91%
Ex. 3
45-63~r 65 / I 59% f SOK ! 22% 46%
From the results set forth in Table I, no correlation between drug content
and release rate can be readily rna.de.
CA 02349017 2001-06-12
It was expected that the formulation of Example 3 would release drug faster
than that of Example 1 because of a higher drug content. However, the in-vitro
release for Example 3 was slower than expected. It is hypothesized that this
is due
to the glass transition temperature of the polymer being lowered (below about
5 37°C) by the high drug content. This situation may or may not be
translated into
in-vivo results.
EXAMPLES 4-9 fSPRAY DRIED)
In Examples 4-9, the bupivacaine base and the polymer utilized in Examples
10 1-3 are once again dissolved in ethyl acetate, but this time the
microspheres are
obtained by spray-drying the solution. Example 4 utilizes a relatively high
drug
content, whereas Example 5 utilizes a relatively low drug content. In Examples
7-
9, microspheres having a substantially similar drug content to Examples 4-5
are
prepared using the solvent e~;traction technique utilized in Examples 1-3.
Details of
15 the formulations are presented in Table 2 below.
TABLE 2
Formulation ~g [onteni
(Theoretical)Yield Process
'
Ex.4 49% 55% Spray-Dried
2 0 Ex. 5 29% 64% Spray-Dried
Ex. 6 45% ~ -- Spray-Dried
Ex. 7 47% - 62ro Solvent Extraction
Ex. 8 28io ~ 74~o Solvent Extraction
Ex. 9 60% 60~o Solvent Extraction
25
With regard to Example 9, the actual percentage of bupivacaine base in the
microspheres is 51%, the molecular weight of the 50:50 dl-PLGA polymer is
18,000, the microspheres were about 45-63 microns, and in-vitro dissolution
CA 02349017 2001-06-12
36
conducted as in Examples 1-3 showed that 61% of the bupivacaine was released
in
22 hours.
The microspheres of Examples 6 and 9 are suspended in a suitable injection
medium (e.g., water) and then subjected to in-vitro dissolution testing via
the
procedures set forth in Examples I-3. The in-vitro dissolution results are
determined for 22 hours.
The in-vitro dissolutions of Examples 4-5 and 7-8 are determined as per the
Examples above, and comparE:d to the dissolution of the bupivacaine free base
and
the bupivacaine hydrochloride salt forms. When compared to pure bupivacaine
l0 base, each of Examples 4-5 and 7-8 showed a distinct retarding effect in
their
dissolution profile. Furthermore, all four examples of the invention displayed
a
small initial burst of drug release which was more pronounced in the
microspheres
prepared by the spray-dried process as compared to the examples prepared by
the
solvent extraction process.
' Scanning electron micrographs of the microspheres for the formulations
prepared by the solvent extracaion and by the spray-dried technique are then
compared. The spray-dried process yields microspheres which are smaller than
with
the solvent extraction process.
Example 10
Local anesthesia Induced by
Controlled Release Microspheres
is Prolonged by Co-Administration
of Dextran Augmenting Agent in the
Infection Solution
Microspheres are prepared which contain 75% bupivacaine, by weight. The
duration of local anesthesia ic~duced by the bupivacaine-loaded microspheres,
prepared from PLGA 65:3 ~, with and without the co-administration of an
augmenting agent, is tested in a rat sciatic nerve model for localized local
anesthesia. In this procedure, groups of rats are selected that demonstrate
normal
CA 02349017 2001-06-12
37
behavior in a leg withdrawal latency test at least a week prior to the
experimental
procedure. The latency test determines the time, in seconds, before a rat
withdraws
its hindpaw from a hotplate set to a safe but uncomfortable temperature
(56°C).
Selected rats are injected with a solution containing a suspension of
bupivacaine-loaded microspheres plus co-administered augmenting agent on one
side and injected with a corn:rol on the contralateral side so that each rat
serves as
its own control. Each injection is adjacent to the sciatic nerve. The controls
are
bupivacaine-loaded microsp:heres without co-administered augmenting agent and
microspheres without any bupivacaine.
A. Sensory Tc.sti~
As previously discussed, the degree of sensory local anesthesia is measured
by determining the time on latency, in seconds, before each rat withdraws its
hindpaw from a hotplate set to a safe but uncomfortable temperature. Maximum
sciatic nerve sensory blockade is defined as having a latency of about 12
seconds or
5 higher.
B. Motor Testing
The degree of motor blockade is measured by scoring the appearance of the
affected foot for the signs of loss of motor tone. The assessment is conducted
as
2 0 follows using a 4-point scale based on visual observation: ( 1 ) normal
appearance,
(2) intact dorsiflexion of fooe with an impaired ability to splay toes when
elevated
by the tail, (3) toes and foot remained plantar flexed with no splaying
ability, and
(4) loss of dorsiflexion, flexion of toes, and impairment of gait.
25 C. Experimental Protocol
Twenty-four rats each receive an injection of bupivacaine-loaded controlled
release microspheres into the left or right side, co-administered with a
dextran
containing injection solution. The contralateral side receive either
bupivacaine-
CA 02349017 2001-06-12
38
loaded microspheres at the same dose, or unloaded microspheres co-administered
with a dextran injection solution.
Sensory hot plate latency is measured from the time of the injections until
the latency declined to under 2 seconds.
Motor blockade is scored until the hind paws of motor blockades rats
returned to a normal appearance.
The dose of bupivacaine contained in each sciatic nerve injection ranges
from 5 to 450 mg/kg of rat or about 1.5 to 50 mg at each injection site.
The tested dextrans has a molecular weight ranging from 20 kDa through
200 kDa. The injection solution containing dextran is buffered to a pH ranging
from7.Oto8.3.
D. Results
On the sides receiving, co-administered dextran augmenting agent show a
significantly longer duration of sensory block and signiFcantly increased
duration of
motor block than do the sides receiving controlled-release bupivacaine-loaded
microspheres without co-administered dextran. Unloaded microspheres with
dextran alone produce no sensory blockade.
Ezam~le 11: Local anesthesia Induced by Controlled
Release Microspheres Is Prolonged
by C:'o--Administration of Alkalinizing
Agents in The Injection Solution
2 5 Preparation of microspheres and testing procedures are as described above.
In this experiment it is shown that co-administration of alkalinizing agents
in the
injection solution serve to significantly prolong the duration of local
anesthesia
induced by the injection of controlled release bupivacaine-loaded microspheres
adjacent to rat sciatic nerve.
CA 02349017 2001-06-12
39
A. Experimental Protocol
Twenty-four rats each receive an injection of bupivacaine-loaded controlled
release microspheres into the left or right side, adjacent to the sciatic
nerve, in
carbonate-buffered injection solution. The contralateral side receives either
bupivacaine-loaded microspheres at the same dose at pH 7.4, or unloaded
microspheres with the same injection buffer as the treatment side. The pH of
the
experimental injection solution ranges from pH 7.0 through pH 8.3.
B. Results
The degree of sensory and motor local anesthesia show a significant increase
in duration proportional to the alkalinity of the carbonate-buffered injection
solution, with the optimum results obtained as the pH approached 8.
Example 12: Local anesthesia Induced by Controlled
Release h~iicrospheres Was Prolonged
by C'.o-Administration Of Agents With
Diverse Pharmacological Activity
In this example, a large number of pharmaceutical agents were tested for
activity in augmenting the duration of local anesthetic activity. Bupivacaine-
containing microspheres at about 75% Loading, by weight, were injected
perineurally into rat sciatic nerve at a dose of 150mg/kg (weight
microspheres/weight rat) to dose of approximately 50 mg/nerve. For the
injections,
needle placement adjacent to tl~e target nerve was optimized by intermittent
electrical a stimulation of the target nerve (via tire injection needle) with
low
amplitude current to produce limb flexion. For the injections, the
microspheres
were suspended in a carrier vehicle suitable for injection. 1~'hile any
pharmaceutically acceptable Carrier vehicle is acceptable, for these
experiments the
TM
carrier vehicle was 1% sodium carboxymethyicellulose and 1% Tween 80 in water.
Compounds to be tested were co-injected with bupivacaine containing
microspheres (i.e., mixed as additives into the carrier vehicle) in a range of
CA 02349017 2001-06-12
concentrations. Results are expressed as percent increase in duration relative
to
non-augmented durations that were obtained in the same animal model.
The duration of anesthi~sia was measured by the hotplate foot withdrawal
method described above in Example 10 and refers to the time necessary for the
animal to recover from maximal nerve latency ( 12 sec) to a latency of 7
seconds,
approximately 50% recovery. The results are tabulated in Table 3 below as
percent
of control.
TABLE 3
Efficacy ofAdditives
to LAB
As Percent of
Control Without
Additive
Addttlve % A,ddttiveDurationPrinciple Pharmacological
AnesthesiaActivity of Additive
CollC.
As Percent
of Control
Allotetrahydrocortisone0.05 100 Steroid, GABA receptor
Allotetrahvdrocortisone0.:~ 117 modulator
Alphaxalone 0.(~3 169 Steroid, GABA receptor
'- modulator and anesthetic
Alphaxalone O..i 123
Aminopyridine 0.05 77 Potassium channel
(4-AP) blocker
Aminopyridine 0.1 1 92
(4-AP)
Amino vridine l.Cl9 131
(4-AP)
Aminopyrine O.C)5 146 Analgesic
Amino urine a 62
0. ~~
Bec>zamil 0.(:X5 83 Sodium channel inhibitor
Benzamil 0.5 154
Clonidine O.CIS 122 Partial a2 adrenergic
agonist
Clonidine 0._' 71 and vasoconstrictor.
CA 02349017 2001-06-12
41
TABLE
3
Efficacy of Additives
to LAB
As Percent of
Control Without
Additive
Colchicine 0.1 677, Microtubule
1308 inhibitor,
Colchicine 1.0 277 inhibitor of
glucose
Colchicine 10 toxic metabolism in
leukocytes
(among other
properties).
Colchicine (Placebo)0.1 0
.
5 Colchicine (no 10 0
LAB)
Dehydroepiandrosteronet0.0~~ Steroid, GABA
receptor
Dehydroe iandrosteronef0.~ modulator
Dextran 3 46-144 Osmotic polysaccharide
Dextran 6 Anesthesia
continued
past
end
of
test
eriod
CA 02349017 2001-06-12
42
TABLE 3
Efficacy of Additives
to LAB
As Percent of
Control Without
Additive
Diazepam 0.0~ 231 Modulates GABA
receptor
Diazepam 0.'.i 203
Diazo~cide 0.05 138 Potassium-ATP channel
-
agonist
Diazoxide O..i 109
5 5,5-diphenylhydantoinO.OS 145, Sodium channel
1 19 inhibitor
5,5-diphenylhydantoin0.11 152
S,5-di hem~lhvd~ntoin1.09 138
Minoxidil O.Oi 54 Potassium channel
agonist
Minoxidil O.:p 218-265
10 Ouabain 0.0~ 154 Na,K-ATPase inhibitor
Ouabain O.p l78
Spantide 0.0~ 1 19 Ncurokinin antagonist
S amide O. i 172
Taxol 0.0~ 188, Microtubule assembly
138
promoter
Ta~ol 0.1 l 104
Taxol 0.~ 82
Tacol 1.09 108
Tetraethylammonium0.0'.i 95 Potassium channel
blocker
Tetraethylammonium0.5 123
r
2 0 U-73, 122' ~ O.O.S l06 "
PLC
inhibitor
U-73, 122' ! 0 1 I S
5
-
-
Valproic Acid 1 ~? Potassium channel
; 0.0~ opener
Val roic Acid 138
O.S
Vinblastine ' 1 ~8 Microtubule iuubitor
0 0~
2 5 Vinblastine ! 37
0 1 1
Vinblastine '4 40
109
t-
CA 02349017 2001-06-12
43
" (1-[6-([17-beta-3-methoxyestra-1,3,5(10)-triene-17-yl]amino]hexl]-1-H-
pyrrole-
2, 5-dione)
EXAMPLE 13 ~EPIi~EPHRINE AS AUGI~IENTII~G AGENT)
Microspheres containing bupivacaine loaded to about 75 percent by weight
with bupivacaine are prepared, with and without added epinephrine, in a
percent
loading of about 0.05 percent, by weight, using the methods described in
l0 EXAMPLES I-3 or EXAIW?L,ES 4-9, above.
Following the protocol set forth in EXAMPLE 10, above, selected rats are
injected adjacent to the sciatic nerve with a solution containing a suspension
of
bupivacaine-loaded microspheres on the right side, and on the left side with a
solution containing a suspension of bupivacaine-loaded microspheres and also
containing 0.05 percent epinephrine.
Sensory and motor testing is conducted according to sections A and B,
respectively, of EXAMPLE I 0, above. Using the experimental protocol of
section
C of EXAMPLE 10, 24 rats are tested.
On the sides receiving a combination of bupivacaine and epinephrine in
2 0 controlled release microspheres, a significantly longer duration of
sensory block and
significantly increased duration of motor block was obtained than with the
sides
receiving controlled-release lbupivacaine-loaded microspheres without
controlled
release epinephrine.
EXAMPLE 14 (A)<I1'FIETAMINE AS AUGMENTING AGENTS)
In experiments conducted according to EXAMPLE 13, above, amphetamine
is substituted for epinephrine, with the same concentrations of each agent. On
the
sides receiving a combination ofbupivacaine and amphetamine containing
controlled release microspheres, a significantly longer duration of sensory
block and
significantly increased duration of motor block was obtained than with the
sides
CA 02349017 2001-06-12
44
receiving controlled-release bupivacaine-loaded microspheres without
controlled
release amphetamine
EXAMPLE 15 (F:PREDRTNE AS AL1G~1ENTING AGENT)
Microspheres containing bupivacaine loaded to about 75 percent by weight
with bupivacaine are prepared, in a percent loading of about 0.05 percent, by
weight, using the methods described in EXAMPLES 1-3 or EXAMPLES 4-9,
above. In addition, microspheres containing added epinephrine, in a percent
loadings of 0.001 percent, 0Ø'i percent and I percent, without bupivacaine,
are also
l0 prepared according to EXAMJ?LES I-3 or EXAMPLES 4-9, above.
Following the protocol set forth in EXAMPLE 10, above, selected rats are
injected adjacent to the sciatic nerve with a solution containing a suspension
of
bupivacaine-loaded microsphe~res on the right side, and on the left side with
a
solution containing a suspension of bupivacaine-loaded microspheres and also
containing epinephrine containing microspheres in each dose level.
Sensory and motor testing is conducted according to sections A and B,
respectively, of EXAMPLE 10, above. Using the experimental protocol of section
C of EXAMPLE 10, 24 rats are tested for each of the three epinephrine dose
levels
by injecting epinephrine-containing microspheres (same number of microspheres
per
rat, adjusted for animal weight) at about the same time as the bupivacaine-
containing microspheres are administered
On the sides receiving a combination of bupivacaine microspheres and
epinephrine microspheres, a si~~nificantly longer duration of sensory block
and
significantly increased duration of motor block was obtained than with the
sides
receiving controlled-release bu,pivacaine-loaded microspheres without
controlled
release epinephrine for each dose level, with the effect showing a dose-
response
curve according to concentration.
As can be appreciated, a substantial range of pharmaceutical agents is
capable of augmenting the duration of local anesthetic activity. In addition,
these
CA 02349017 2001-06-12
45
compounds were tested as additives in the vehicle suspending the microspheres.
Including an augmenting af;ent into the controlled release formulation itself
is
expected to substantially improve the prolongation of Local anesthetic
activity by
prolonging the presence of augmenting agent at the anesthetized site.
The examples provided above are not meant to be exclusive. Many other
variations of the present invention would be obvious to those skilled in the
art, and
are contemplated to be within the scope of the appended claims. Numerous
publications are cited herein, the disclosures of which are incorporated
herein by
reference in their entireties.
