Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
25,16n
'1~4597~i ;
BACKGROUND OF THE INVEN~ION
~ his invention relates to the controlled release of
drugs. The time of release of medicament~ or drugs can be in
part co~trolled by incorporating the drugs i~ a matrix of a~
enzymaticall~ degradable form of polg(N-acetyl-D-glucosami~e)
~o that said form i~ slowly enzymatically degraded over a
period of time by body fluids and the drug i9 released into
the body fluids at the time of use for a longer period than
~he drug would be released without the matrix carrier. ~;
~e prior art shows many efforts over a long period
by many individuals to alter the rate of release of drugs.
Where it is considered that drugs may be administered to many
areas and for man~ different conditions and that various drugs
have different solubilities in both water and oil, and the
period for desired administration may varg from almost i~-
stantly to a long period of up to and including years, it càn
be ~een that there is a wide range of medicaments and a wide
range of conditions to be controlled.
,
DESCRIPTIO ~
U. S. Patent 2,552,027, Bird and Rochow, May 8, 1951,
CAS~ING GELATIN ~AB~E~S, discloses the incorporation of medica-
ments~ particularly vitami~s, into a gelatin-glycerine matrix,
which are "particularly useful for the administration of vita-
~ ins or other pharmaceutical materials which should be released25
in the stomach or digestive tract at comparativel~ slow rates."
In U. S~ Patent 3,604,417, Stolzenberg and Linken-
~; heimer~ September 14, 1971, OSMOTIC FLUID RESERVOIR ~OR OS-
MOTICA3LY AC~IVA~D IO~G-~E~M CO~TINUOUS INJ~CTOR DENICE osmo-
tic pressure i8 used to propel a piston system so that a drug
i8 810wly injected.
Many coating systems have been used on tablets for
enterio release in which various capsules have been coated
-1- ,~ `
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~5~75
either a~ a single tablet or by coating particles in the tab-
lets or capsules so that drugs are released into the stomach
or intestine at a controlled rate and for a longer period tha
would result from the administration Or the medicam~nt without
such coatings.
U. S. Pate~t 3,739,773, Schmitt and Polistina,
June 19, 1973, PO~YG~YCO~IC ACID PROSTH~IC DEVIa~S, in Col-
umn 6~ line 53, refers to polyglycolic acid in combination
with other products as slowly digestible drug release devices.
This patent in Column 7, lines 47 and following, mentions that
d~es, antibiotics, antiseptics, anesthetics, and other ma-
terials may be present in polygl~colic acid devices. ~his
la~t language also appears in Column 3, line 48 and following
o~ U. S. Patent 3,297,033, Schmitt and Polistina, January 10,
1967, SURGIC~L SU~URES.
U. S. Patent 3~435,008, Schmitt, Epstein a~d Poli-
~tina, ~arch 25, 1969, METHOD ~OR PREPARATIO~ 0~ ISOMERI-
CA~LY PURE ~-G~YCO~IDE AND PO~YMERIZA~IO~ M~OD ~OR G~YCOLID~
COMPOSI~ION~ ~MPIOYI~G PARTIAL HYDRO~YZATE 0~ SAID ~-G~YCO~ID~
in Column 7, line 19 and following, discloses glycolide poly-
mers as coatings ror medicaments to alter their digesti~e
characteristics.
U. S. Serial ~o. 179,129~ available through conven-
tion documents in the file o~ Netherlands 7,212,272, in Ex-
ample 14 discloses a bioerodible ocular insert containing -~
pilocarpine using a matrix of polyglycolic acid. Pilocarpi~e
i~ mixed with polyvinyl alcohol and used as a core between
two sheets of polyglycolic acid. tsee page 112). Page 60
discloses polyester~ of lactic a~d glycolic acid as a carrier.
Page 739 line 11, mentions "chitin" among other polysaccha-
rides and plant hydrocolloids. Presumabl~, the reference i~
to the naturall~ occurring form of chitin. ~laim 5 i~ drawn
-2-
; . .
. ~- , . ~, . .
~ `^ ~
~45~7S ~;
to bioerodibility by e~zymatic cleavage. Claim 14 is drawn
to cross-linked gelatin. Claim 50 i9 drawn to polylactic or
polyglycolic release rate controlling materials.
Sterile peanut oil and similar materials have been
used as a repository for penicillin for some time. The peni-
cillin is slo~ly released from the repository. Unfortunately,
the peanut oil or beeswax remains behind and is apt to form
a sterile abscess rather than be absorbed by tissues.
C~rboxymethylchitin is disclosed in Carbohyd. Res.
7, 483-485 (1968), Ralph Trujlllo.
This article mentions the hydrolysis of both chitin
and carboxymethylchitin by lysozyme.
Chitin has been estimated to be the second most
abundant polysaccharide in nature with a synthesis in the
neighborhood of a billion tons a year by marine organisms.
See Chitin, N.V. Tracey, Reviews of Pure and Applied Chemi-
stry, Royal Australian Chemical Institute, Vol. 7, No. 1,
March 1957, Pages 1-14.
` The above patents and articles describe chitin, its
properties and derivatives.
Although it is well recognized that systems for
tha controlled release o~ drugs are very much in demand, the
wide range of requirements is such that useful contributions
are still being sought and major efforts are being made by
many research organiæations to improve drug delivery device$.
SUMMARY OF THE INVENTION
- ~ .
It has now been found that enzymatically degrada-
ble forms of poly(N-acetyl-D-glucosamine) sometimes herein
abbreviated as PAG, are comparatively storage stable and re-
sistent to hydrolytic degradation so that medicaments may be
incorporated and stored in a matrix of such biodegradable form ~4
-- 3 --
~'` ~ ' '
.
, . ~
, .
g7S ,~
PAG, and the medicament then released in the tissue of liv-
ing mammals by the enzymatic degradation of the biodeqrada~
ble form of PAG. The enzyme lysozyme is particularly effec-
tive in the enzymatic degradation of the biodegradable forms
of PAG. Various forms of PAG may have different degradation
rates, and the degradation rate may vary with the location
of the drug release device.
Usually it is desired that the drug release device
be mechanically acceptable at a location of use. For instan-
ce, an ocular insert may be designed to be placed adjacent tothe eyeball inside the eyelid, in the cul-de-sac of the con-
junctiva between the schlera of the eyeball and the lid. An
insert needs to be soft so that it will cause a minimum o
irritation to the eyeball and the degradation products are
preferably such that they may be washed away by the flow of
tears without the necessity for removal of the device after
its drug content has been delivered. For other locations, `~
such as implantation beneath the surface of the skin or in-
sertion in the utuerus as an anti-fertility device, the like- ~ ;
lihood of irritation from the mechanical aspects of the de-
vice are much less. `
Because the requirements ~or use in the eye are `
! among the more rigorous, the present device will be described
particularly in conjunction with the use in the eye although
it is to be understood that the device in its many forms may
be used in other locations.
N-acetyl-D-glucosamine has the formula: ~
~ `
- 4 -
~ .
~5,160
,. ..
.. .
;^ 6
~: 1~* ~
~ ~ 1 or
NHCCH~
'~ 10
HO 4\~
;~s~ HCC~ ~H
~ O
Groups below the plane of the paper are shown b~ a dotted bond.
~i' Pol~ acet~l-DLglucosamine~ has ascribed to it the
formula (ring h~drogens omitted for clarit~)
r, ' . .
6 ~2 ~ ~IO~ I C
~ ~5 ~.~"~
HAC ~ OH
Poly(~-acetyl-D~glucosamine) is a ma~or component of
',l naturally occurring chitin. ~he naturally occurring material
has not only the poly(~-acetyl-D~glucosamine) but also inor-
ganic salts thought to be forms of calcium carbonate and
proteinaceous material, the composition of which is not pre-
3 sently known. The term "chltin" is used herein to refer to
I the various naturally occurring forms of~chitin including
the protein and inorganic carbonate components. ~he term
1l
i ~ '. , ~ ' I
~ ~ . . .. ..
l --
; 25,160
1045~75
"purified chitin" i9 used to refer to chitin after purifica-
tion to remove calcium carbonate and other inorganic salts
and various proteins which may be present and is essentially
poly(N-acetyl-D~glucosamine). Some confusion exist-~ in the
; 5 literature in that the name chitin is used as a name ~or
poly(N-acetyl-D~glucosamine~ without specirging whether it
is a naturally occurring material containing inorganic salts
~ and proteins or whether the term is intended to designate
purified poly(~-acetyl-D-glucosamine) without specifying the
.~ 10 degree of purity or the character o~ the impurities present.
~he term "enzymatically degradable form of poly(~-
-acetyl-D-glucosamine)" refers both to the purified poly(N-
-acet~l-D~glucosamine) from chitin itself as well as the
carboxymethyl, hydroxyethyl, and O-ethyl derivatives, etc.
~he carboxymethyl derivative, properly called `~
poly~N-acetyl-6-0-(carboxgmeth~l)-D~glucosamine] has the `~
:J~ :
I formula ~
~:
~I HO ;
' 20 Q~ oc~ COOH ~ ~ ~c
;' "0~ = ~"`0/
~ ~ ~ELAc C~ OC~ COOH
.i
~he hydroxyethyl derivative, properly called
poly~N-acetyl-6-0-(2'-hydroxyethyl)-DLglucosamine] has the
formula
',,s~
.',
:
i ' ~ .
25,160
"
~ ~04597S
, .
OC~ CH~ 0~ ~0, NHAc ~ ~
o~ o~' ~-
Ac 4 C~2 C~2 CH~ S)E
~he O-ethyl derivative, properly called poly-
~: rN-acetyl-6-O~(ethyl)-DLglucosami~e~ has the formula
~' 10
.` CH~OC~ C~ HO ~ c
~ 15 XO ~ c CE~OC~ CH3
j~ ' III
~he above forms are sometimes hereinafter designated
~ by the Roman Numeral below the ~ormula.
`~ Other similar derivatives which are enz~matically
: 2 degradable, particularly by lysozyme, are included within the
eneric term "enzgmatically degradable form o~ poly(~-acetyl-
_~Lglucosamine)~.
~ ~¢ause o~ the nature of the polgmers~ carboxymethyla-
:~ tion, hydroxyethylation, or ethylation may not be 100%, and
may in part o¢cur on the 3-hydroxyl. Unle~s otherwise speci-
` fied~ under or over-substitution Or the pol~[N-acet~1-6-0-
(carbox~methyl~-D-glucosamine] is to be included as a biode-
: ~ gradable form of PAG. ~he solubilit~ in a specified solvent
:~ is one test of the degree of substitution. ~or example, the
O-ethyl derivative is water ~oluble when the eth~l group to
glucosamine ratio is about 1 and organic soluble when the degree
of ~ubstitution is greater than 1.
,~
~:~ : ~7 I
; . ., .;
~ 5~75
The term "drug" is used to refer to a substance other
than a food intencled to affect the structure or function of
the body of man or other animal. The term is somewhat broad~
er than "medicine" in that the term "medicine" is sometimes
considered to be restricted to an agent which is administered
to affect or control a pathogenic condition. The broader term
"drug" here is also used to include steroids and other fertil- -
~,; ity controlling agents which may be incorporated in an intra~
uterine contraceptive device or other materials which may he -
., , ~
included to affect the fertility of females or males either
~; as an intrauterine device or subcutaneously.
$~ The term "dispensing" is used to designate a method
of administering a drug to man or other animal and includes
the release of the drug to a desired location. This would in-
clude the eye, gastrointestinal tract (alimentary), intrauter-
inely, intramuscularly, subcutaneously, or into the mucosa of
the nose, mouth (sublingual), or rectum, etc. The release
over a prolonged period of time designates any decrease in the
release rate of the drug over that which would be expected if
. ':
. ; 20 the drug were administered alone and would include from the
matter of a few minutes as, for example, in an ocular insert
containing pilocarpine to a duration of six months to a year
which might be desired for the administration of a steroid in
,l an intrauterine contraceptice device. For some conditions,
even a longer period o administration, such as the lifetime
~ of the patient, could be desired but usually a period of a
'~ very few hours up to about six months includes the medically
preferred range. ;;
Because the enzymatically degradable form of poly-
~; 30 (N-acetyl-D-glucosamine) is a solld which can be removed, a
long-acting repository pellet for insertion beneath the skin
~i~ is quite practical as if for any medical reason it is desired
- 8 -
~4~75
to discontin~e administration o~ the drug, the insert with
the remaining drug charge may be removed simply by excision.
The term "enzymatically degradable" refers to a form
of poly(N-acetyl D-glucosamine) or its derivatives which is
broken down into body fluid soluble components and which are
washed out as in tears, or transported elsewhere by tears, or
other body fluid, and later degraded further or metaboliæed
by the body or excreted by the body. The problem of retention
by the body or disposal of the residual matrix is minimal or
non-existent.
While other enzymes may also affect the enzymatic
degradation of the poly(N-acetyl-D-glucosamine) matrix, the
enzyme which is most widely distributed in the body and here
very effective is lysozyme. Lysozyme occurs in practically
all of the body fluids, particularly the tears, and effective-
ly breaks down the polymer chain to water soluble or disposa-
ble components.
Chitosan, which is a common name for the deacylated
form of poly(N-acetyl-D-glucosamine), and which is poly~D-
-glucosamine) is not enzymatically degradable by lysozyme.
By contrast, the present enzymatically degradable
forms of poly(N-acetyl-D-glucosamine) are not readily hydro-
lyzed by water. For instance, I in a phosphate buffer at PH
7.2 at 37C for 24 hours is not hydrolyzed whereas under the
same time and temperature in the presence of lysozyme hydroly-
sis occurs.
It is highly advantageous to have the degradation of
the enzymaticalLy degradable form of poly(N-acetyl-D-glucosa-
mine) occur only by the action of an enzyme as the resistance
to hydrolytic degradation markedly reduces problems of manu-
facture and storage in the presence of ambient moisture, and
ensure a steady smooth surface erosion rather than a
_ 9 _
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~ )4597S
fragmentation process commonl~ experienced b~ pol~mers which
are hydrolyæ sd by smal 1 mol ecul e s .
Any of the drug~ used to treat ~he eye and surround-
ing tissues can be incorporated with the enz~maticall~ de-
5 gradable form of PAG of this invention. Also, it i~ practi-
cal to use the e~e and surrounding tissues as a point of entr~
- for s~stemic drugs that enter circulation in the blood stream
and produce a phaxmacolo~ical response at a site remote from
the point of application o~ drug and the enz~matically de-
gradable ~orm of PAG matrix. ~hus, drugs which will passthrough the e~e or the tissue surrounding the eye to the blood-
stream, but which are not used in therapy of the eye itself,
can be incorporated in the enzymatically degradable PAG matrix.
~uitable drugs for use in therap~ of the eye with
the present insert include, without limitation: Anti-in-
~ectives: such as antibiotics, including tetracycline, chlor-
tetracycline, bacitracin, neomycin, polymyxin, gramicidin,
oxgtetrac~cline, chloramphenicol, and erythromycin; sulfona-
mides, including sulfacetamide, sulfamethazole, and sulfisox-
azole; antivirals5 including idoxuridine; and other anti-
-infectives including nitrofurazons and sodium propionate;
Antiallergenics such as antazoline, methapyrilene, chlor-
pheniramine, p~rilamine and prophenpyridamine; Anti-inflamma-
tories such as h~drocortisone, hydrocortisone acetate, dexa-
methasone, triamcinolone, medr~sone, prednisolone, predniso-
lone 21-phosphate and prednisolone acetate. Decongestants
such as phen~lephrine, naphazoline, and tetrahydrazoline.
Miotics and anticholinesterases such as pilocarpine, eserine
salic~late, carbachol, disopropyl fluorophosphate9 phospholine
iodide, and demecarium bromide; matropinej scopolamine, tropi-
camide, eucatropine, and hydroxyamphetamine and Sypathomine
tics ~uch as epinephrine. Drugs can be in various ~orms,
10-
,
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~ 0~5~7~
~uch as unchanged molecule~, components o~ molecular com-
plexes, or nonirritating, pharmacologically acceptable salts9
such as hydrochloride, hydrobromide, sulfate, phosphate,
nitrate~ borate, acetate, maleate, tartrate, salic~late, etc.
Furthermore, simple derivatives of the drugs (such as ethers,
esters~ amides, etc.) which have desirable retention and re-
lease characterics but which are easily hydrolyzed by body
pH, enzymes, etc. can be employed. The amount of drug in-
corporated in the ocular insert varies widely, depending on
the particular drug, the desired therapeutic effect, and the
time span for which the ocular insert will be used. ~ince
the ocular insert is intended to provide the complete dosage
regime for eye therapy for but a particular time span, such
` as 24 hours, there is no critical upper ~imit on the amount
~ drug incorporated in the device. ~he lower limit will
depend on the activity of the drug and its capability of being
released from the device. ~hus, it is not practical to de~ine
a range for the therapeutically effecti~e amount of drug in-
corporated into the device. However, typically, from 1 micro-
gram to 1 milligram of drug is incorporated in each insert.
In each case~ the pol~meric material used to formthe ocular insert is chosen for its compatibility with a parti-
¢ular drug and its capability of releasing that drug at an
appropriate rate over a prolonged period of time. Specific,
but nonlimiting, examples of combinations of drugs and poly-
mers for use in forming the ocular insert include: poly-
~N-acetyl-6-0-(carboxymethyl)-~gluco~amine] and epinephrine;
poly~-acetyl-6-0-(carboxymethyl)-D~glucosamineJ and mixture
of pilocarpine hydrochloride and epiniphrine; poly[N-acetyl-
-6-0-(2'-hydroxyethyl)-D-glucosamine] and acetRæolamide;
poly[N-acetyl-6-0-(ethyl)-D~glucosamine] a~d phospholine
iodide; poly[N-acetyl-6-0-(carboxymethyl)-DLglucosamine] and
-11-
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, .. . .
....
. .. . . .
.
25, 16~ -
~3L04S~75
triamcinolone~ or in general any of the drugs listed above
and the enzymatically de~radable form Or poly(N-acetyl-D-
-glucosamine), including degrees of substitution greater or
les~ than 1, and related derivatives such as other lower
alkyl derivatives instead of poly[~-acet~1-6-0-(ethyl)-D-
-glucosamine], other carboxyalkyl derivatives, and their esters
and salts, hydroxyalkyl derivatives, etc.
~he degradation rate of the enzymatically degradable
form of poly~-acetyl-D-glucosamine) can be lowered by cross-
linking, if a slower release rate is preferred.
The ocular insert can be fabric~ted in any convenient
shape for comfortable retention in the cul-de-sac. It is im-
portant, however, that the device have no sharp, jagged, or
rough edges which can irritate the sensiti~e tissues of the
eye. ~hus, the marginal outline of the ocular insert can be
ellipsoidal, bean-shaped, rectangular, etc. In cross section,
it can be concavo-convex, rectangular, etc. As the ocular
insert is flexible and, in use, will assume essentially the
configuration of the scleral curvature, the original shape of
the device is not of controlling importance. Dimensions of `
the device can vary widely. ~he lower limit on the size o~
the device is governed by the amount of the particular drug to
be applied to the eye and surrounding tissues to elicit the
desired pharmacological response, as well as by the smallest
sized device which conveniently can be inserted and removed
from the eye. ~he upper limit on the size of the device is
governed by the limited space within the cul-de-sac that
conveniently and comfortably can be filled with an ocular
insert. ~ypically, the ocular insert is 4 to 20 millimeters
in leng~h, 1 to 12 millimeters in width, and 0.1 to 1 milli-
~eter in thickness. Pre~erably, it i8 ellipsoidal in shape ~-~
and about 6 x 4 x 0.5 millimeters in size. ; ~
: ,
;12~ ~
. . .
25,160
lV4~597 ~
While particularly convenient for an insert in the
eye1 the matrix containing the drug of the present invention
can include other drugs for other areas. ~or instance, if
the drug i9 to be taken orally, a tablet of a size and shape
adapted to being swallowed i8 preferred. If it is to be
placed subcutaneously, a tablet or rod such that it may be
placed under the skin in an appropriate location is selected.
~he amount of drug and the time over which it is to be dis-
pensed are controlling i~ the choice of size of the implant.
While the drug may be combined with the enz~mati-
cally degradable form of PAG matrix in any co~venient way, it
i8 particularly convenient to dissolve both in a common sol-
vent which permits casting of the enz~matically degradable
~orm o~ P~G as a matrix containing the drug to be dispersed
therein.
Poly(N-acetyl-DLglucosàmine~ is reported to be in-
~oluble in all solvents except 88% phosphoric acid which badl~
degrades the polymer. Unexpectedly, it has ~ow been found 3
that hexafluoroisopropanol ~XIPA) and hexafluoroacetone ses-
~uihydrate (HFAS) are solvents for the polymer. These are
extremel~ powerful solvents~ and so much so that care must
be used in selecting drugs which are compatible with such
solvents to form solutions ~or casting.
PolyCN-acetyl-6-0-(carboxymethyl~-DLglucosamine], I,
poly~-acetyl-6-0-(2'-hydroxyethyl~-D-glucosamine], II, and
poly~N-acetyl-6-0-(ethyl)-D~glucosamine]~ III, are pre~erred
I because of cosolubility with many drugs in common solvents,
¦ including water. Non~toxic solve~ts are preferred.
I and II are water soluble at the ~% level, and
III is water soluble at the 5% level if the degree of substi-
tution is not more than about 1, and organic solvent soluble
if more than about 1. Organic solvents ma~ be used such as
~,..................................................................... .
-,-- - . ., 1
, : . '. ' ' . . : , .
25,160
:10~5975
alcohol~, chloro~orm, benzene, toluene, mixtures of benzene
and toluene with alcohols and ketones.
Pilocarpine or other drugs can be incorporated into
matrices of these en~ymatically degradable forms of PAG by
hydrogen bonding, covalent bonding, ionic bonding or simple
entrapment. The matrices themselves can be variably cross-
linked with a variety of physical and chemical agents. The~
can be sterilized and when hydrated become quite pliable, while
retaining adeguate strength to resist manipulation.
Present day therapy of topical drug application
consists of drops and ointments. There are several defici-
encies associated with these methods of delivery ~ it is
impossible to achieve 24 hour control of the disease (2) it
i8 wasteful with respect to the amount of drug used (3~ some
people show strong sensitivity to cholinergic and adrenergiG
drop~ (4) many patients fail to apply the medioation as di-
rected resulting in poor control of the disease (5) side ef-
fects result from the drug passi~g through the lachrymal duct
into the circulatory system. The herein described invention
eliminates these problems and provides a means of releasing
medication into the tear films in therapeutic levels con-
; tinuously. ~he device is biodegradable and, hence, it is not
~ecessary to remove from the eye and also capable of deliver-
ing large dosages giving it broad drug applicability. ~his in-
vention constitutes a more efficient means of drug delivery
that prolongs and enhance~ the drug effect.
As the scope of this invention is broad, it is ~1-
lustrated b~ the following typical examples in which tempera-
tures are centigrade, and parts are by weight unless clearl~
, .
I 30 otherwise specified.
,. .
:. . , ' . , - ,' ~ ' ;
25,160 ~~
i0 ~ ~9~5
~ .
Purification 0r Chitin
_
A commercial grade of chitin (Cal-Biochemicals)
was finely ground in a ball mill overnight to pass a 6 mm
screen and be retained by a 1 mm screen. 149 g. of thîs
fi~ely ground material was decalcified by extracting with
825 ml. of 2N HCl at 4C for 48 hours, in a flask stirred
with a magnetic stirrer. The material was collected by
¢entrifugation and washed repea~edly with water until neutral.
~he ash content was 0.4-0.5%. ~he decalcified chitin was then
stirred at room temperature with 1500 ml. of 90% formic acid
overnight. The mixture was centrifuged and the residue re-
peatedly washed with water. The washed chitin was then sus-
pended in 2 1. of 10%NaOH solution and heated at 90-100C.
for 2.5 hours. he solution was filtered, the cake washed
with water until neutral, washed several times with absolute
ethanol and ether, and dried at 40C. under reduced pressure;
I yield 66 g. of poly(N-acetyl-D-glucosamine). Infrared spec-
¦; trum (EBr pellet) shows bands at 3500 cm~l (S), 2900 (W),
1 20 1652 (S), 1619 (S~, 1550 (S), 1~70 (S), 1300 (M), 1070 (Broad).
(S is ~trong, M is medium, W is weak).
E~ample II
Poly~N-acetyl-6-0-~carboxymethyl~-D-glucos~mine]
15 g. 0r the poly(~-acetyl-D-glucosamine) from Ex-
ample 1 was swollen with 100 ml. of dimethylsulfoxide (DMS0).
To this highly swollen suspension was added 400 ml. of 2-pro-
panol and the mixture stirred vigorously under nitrogen while
40 mlO of 300io agueous NaOH was added over an interval of 30
minutes at room temperatureO After stirring for an additional
hour, 18 g. of chloracetic acid dissolved in 40 ml. of water
was added dropwise over a 30 minute period~ The mixture was
then heated at 55C. for 24 hours. The mixture was decanted
-15-
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- . : . . . : . .
,, ,
~5~160 ~
10~975
and to the residue was added 100 ml. of 70~ methanol. ~he
suspension was then neutralized with 5 ml. of 90% acetic acid~
m e mixture was filtered, washed with 70% methanol, absolute
methanol and dried at 40C. in vacuo Yield 24 g. of poly-
~N-acetyl-6-0-(carboxymethyl)-D~glucosamine]~ I. Infrared
(~Br pellet) shows bands at ~00 cm 1. (S), 2900 ~M), 1600
Broad (S), 1400 (M), 1320 (M), 1100 Broad (S) D A sample was
titrated and shown to have 4.03 meg acid/g indicating 100%
o~ the repeating mers were carboxylated. ~ilms easily re-
moYed from glass were cast from water solution and shown to
be transparent, flexible and tough.
Example III
Preparation of pol~(D~ _samine3 ~ ;
,,
A procedure similar to that described by P. Brous-
signoc, Chemie and Industrie, 99 (9) (68~, 1243 was used. ~o
a solution of 180 g. of 96~/o ethanol and 180 g. ethylene gl~col
was added 360 g. ~OE with stirring. ~o this solution was
then added 54 g. of poly(~-acetyl-DLglucosamine) (purified
I~ Chitin) from ~xample I and the mixture heated at 120C. for
¦ 20 6 hours. After cooling an equal volume of water was added
to the mixture. ~he mix~ure was filtered and washed several
times with water until neutral, then twice with acetone, and ~ ;
dried in vaauo. Yield 42~6 g. of poly(DLglucosamine)~ some- ;
times called chitosan. Infrared spectrum (EBr pellet) showed
bands at 3450 cm 1~ (S), 2900 (M), 1620 (S~, 1600 (S), 1370
~tBroad (S)~; 1050 ~Broad (S)]. Upon potentiometric titration
of the sample 81.4~ of the mers were found to be deacylated.
~ he prod~ct is soluble in 3% acetic acid and forms clear,
T~ flexible~ tough films from this solution. It is not enzymati-
cslly biod-gradsble by lysoz~me.
f~
--16
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:` .` : , ,
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D~Glucosamine~Pilocarpine Film
~ o 5 ml. of 3% acetic acid wa~ added 0.25 g. of
p~ly(D-glucosamine~ from Example III~ ~o the solution thus
formed was then added 50 mg. pilocarpine free base and 100 ul
of tritiated pilocarpine, and the mixture was cast a a film
~40 mil wet thickness) on glass. This film was crosslinked
by dipping the film in 37% formaldehyde solution for 5 hours.
æhis film showed zero order release over a period of 3 days at
which time it was still releasing pilocarpine at a zero order
rate. About 70 percent of the pilocarpine remained in the
film matrix after 3 days. ~he use of tritiated pilocarpine
permits the use of a liquid scintillation coun~er to monitor the
j release rate accurately and conveniently. ~adiological hazards
are associated with such tritiated material in the treatment
of human subjects so experimental animals are preferred to
I ~tudy release rates.
Il ~e~Z
.
Pol~[N-Acet~1-6-0-(aarboxymeth~l)-DLGlucosa ine]/Pilocarpine Fil
~o a 5% solution of poly~-acet~1-6-0-carboxymeth~l)-
-DLglucosamine] (0.95 g.) in water was added 50 mg. of pilo-
carpine nitrabe and 100 ul Or tritia~ed pilocarpine. A film
40 mils thi¢k was cast on a glass ~late and allowed to dry.
~he film was crosslinked by dipping into 10% alum for 5 hoursO
Release of pilocarpine ~rom this ~ilm in an agueous solution
approximating human tears is essentially first order, with
90% of the pilocarpine being released within about 5 hours.
~xample VI
Pol~(N-Acetyl-D-Glucosamine) Matrix
Membranes of poly(N-acetyl-D-glucosamine~ were pre-
; pared by dissolving poly(~-acetyl-DLglucosamine) in each of
hexafluoroacetone sesguihydrate (l.4h solution) and hexa-
17
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fluoroisopropanol (2% solution~. The films were tough, tran~-
parent, non-tacky, flexible and were guite pliable when hy~
drated yet retained adequate strength to resist manipulation.
~he membranes showed no hydrolysis after exposure to water ~or
5 days~ In the presence of l~sozyme, however7 the films were
degraded slowly. ~he films eroded release any drug in the
.:
film slowly.
~xample VII
Biodegradability of Pol~[~-Acetyl-6-0-(Carboxymethyl~-D
~Glucosamine~
After 24 hours incubation at 37C. in phosphate , ,
buffer pH 7~2 containing 1500 units/ml of lysozyme, polytN- ~
-acetyl-6-0-(carboxymethyl)-D~glucosamine~ was hydrol~zed to ,~,,
oligomers as deter~ined by Gel Permeation Chromatography. A
control containing no enzyme was not hydrolyzed under the
same condition~.
Example VIII
~1 In Vivo Results Using Poly~N-~cet~1-6-0-(Carboxymeth~l)-D-
l ,-Glucosamine]/Pilocar~ine
~ 20 Membranes of poly[~-acet~1-6-0 (carboxymethyl)-D- ~,
,~ -glucosamine] were evaluated in vivo for sustained pharmacolo- -
gical e~fect and eye irritation. I~ the right eye of each of
.
three rabbits was placed a 1 mm x 10 mm film strip of pol~N-
-acetyl-6-0-(carboxymethyl)-DLgluco~amine~ (0.25 g. polytN-
-acetyl-6-0-(carboxymethyl)-D~glucosamine]/0.64 g. pilocarpine~
I Within 15 minutes after implantation of the film strip a sub-
stantial lowering in pupillary constriction was observed and ;'
lasted approximately,6 hours. ~he membranes were well tolerated ~'
and slowly eroded in the eye. Such a prolonged effect in
rabbits can be extrapolated to a 24 hour effect in humans since
the rabbit metabolizes pilocarpine more rapidly than a human.
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Pol~rN-Acet~1-6-0-(2 ' -Hydrox~eth~l ~-D Glucosamine]
Inko a screw cap bottle was placed 13.6 Es. 0~ puri-
fied PAG milled so that it passes a 1 mm. sieve. ~o the
bottle was added 200 ml. of cold tO-5C. ) aqueous 43% NaOH
a~d the contents stirred for 2 hours u~der nitrogen and then
held at 0-5C. for lO hours. ~he swollen alkali derivative
was then sgueezed to 3 times its original weight in a sintered
glass ~unnel, disintegrated and frozen at -20a. under nitro-
gen for l hour and then thawed at room temperature for l hour.
~he freeze-thaw cycle was repeated 3 times. ~o the alkali ~
derivative was then added 120 ml. of dimethylsulfoxide (DMS0~ -
and the slurry added immediately to a stirred autoclave. ~he
autoclave was purged several times with nitrogen and 53.2 ml.
of ethylene oxide was added (16 equivalents/equivalent of PAG).
~he mixture was held at 50CC. for 18 hours. ~he solution was
then carefully neutralized with glacial acetic acid, dialyzed
~nd then lyophilized.
.i~
~he hydroxyethyl derivative can be further purified
b~ precipitatin~ the polymer from aqueous solution with acetone.
i ¦
A fre~hly precipitated 3ample of poly~N-acetyl-6-0-(2'-hydroxy-
ethyl)-D~glucosamine] readily dissolved in water, 5% aqueous
~odium hydroxide, and 3% acetic acid and is precipitated from
~ these solutions by acetone. Samples analyzed for C, H and
yj 25 showed the composition to be one in which 1.5 hydroxyethyl
groups had been substituted per glucosamine residue.
., .
Example X
Pol~EN-Acet~l-6-o-(Eth~ DLGlucosamine]
~he procedure of ~ample IX was followed except 75 ml.
3 of ethylchloride was added i~stead of ethylene oxide and the
reaction held at 50C. for 15 hour~. A water soluble deriva-
tive is obtained.
~,
9_
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,. . ~.
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~o obtain an organic soluble derivative, the ethyl-
chloride was mixed with benzene (75% of the amount Or ethyl-
chloride). The reaction time was 10 hours and the temperature
was controlled as follows: 1 hour heating up to 60C., 1 hour
heating up to 80C., 1 hour heating up to 130C. and 7 hours
at 130C. An organi~ solvent soluble product was obtainedO ~he
following solvents are useful for solubilization (5% solution)
of this polymer at room temperature 0-xylene, benzene, tolu-
ene, methylethyl ketone, 1.4 mixture of alcohol~and benzene,
chloroform and alcohols.
~; In the following example using pilocarpine free base,
the drug is bound ionically to the polymer. ~he attractive
~ features of such a system are (1) slower drug delivery and
¦ (2) capability of delivering pilocarpine as a free base which, ` ;
as such, has a higher potency. Up to now, it was not possi- ; !
ble to delivex pilocarpine as the free base since it is un- ~
.:
stable in this form and as a result is usually delivered as
the hydrochloride or nitrate salt.
Ex le XI
1~: : .
Pilocarpine/Poly~-Acetyl-6-0-(Carboxymethyl)-~Glucosamine]
In~erts
A 5% solution of poly[~-acetyl-6-0-~carboxgmeth~l)-
-DLglucosamine~ was prepared in deionized water. ~he solution
j was acidified wibh acetic acid and the polymer precipitated
by slowly adding this solution to acetone. ~he polymer was
dried in vscuo at 40C. overnight. Films were prepared from
5% agueous solutions containing the following relative weights:
Poly~N-Acetyl-6-0-(Carboxy- Drug Dose per
Pllocar~ine meth~ D~Glucosamine _ _ 1.5 mg. Strip
9.1 mg 90.9 mg 0.10 mg
o 19.4 mg ~0.6 mg 0.24 mg
33-3 mg 66.6 mg 0.50 mg
. . . .
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7 5
~he films were cut into strips approximately 1 ~m x
10 mm weighing 1.5 mg each. In this ma~ner, the drug dosages
are delivered from each respective strip, when inserted in the
eye.
5Effective medication for a treatment day is obtai~ed
b~ placing an insert 1 mm by 10 mm in the human eye.
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