Note: Descriptions are shown in the official language in which they were submitted.
20389~9
1 ARC 1800
COMPOSITIONS COMPRISING CYTOTOXIC AGENT
AND PERMEATION ENHANCERS
FIELD OF THE INVENTION
s
This invention relates to the delivery of cytotoxic agents.
More particularly, this invention relates to novel compositions for
enhancing the percutaneous absorption of cytotoxic agents. Still
more particularly, but without limitation thereto, this invention
relates to the delivery of a cytotoxic agent such as 5-fluorouracil
to the skin utilizing a permeation-enhancing mixture of a lower
alkanol, propylene glycol or a mixture of polyethylene glycols, and a
third permeation enhancer.
BACKGROUND OF THE INVENTION
Traditional treatments of malignant tumors of the skin such as
actinic keratosis and superfic;al basal cell carcinoma and non-
malignant skin disorders such as psoriasis have included daily or
more frequent application of cytotoxic agents such as fluorouracil
with or without an occlusive dressing to the affected area.
Penetrating solvents have been investigated for enhancing
percutaneous absorption of certain cytotoxic agents in an effort to
more successfully treat more resistive conditions. Severe skin
inflammation from damage to treated tissue by the cytotoxic agent
typically occurs with this treatment, severely limiting its
usefulness.
.
-~ A method based on the timing of administration of a cytotoxic
~ 30 agent in a penetrating solvent, preferably without occlusion, is
-~ d;sclosed in U.S. Pat. Nos. 4,82~,711, 4,849,426 and 4,853,388 for
the treatment of actinic keratosls or psor;asis with less damage to
~ treated t;ssue.
:` 35 Fluorouracil (5-fluorouracil or 5-FU) is a fluorinated
pyrimid;ne ant;neoplastic agent that acts as an antimetabol;te to
uracil. It interferes with DNA synthesis by inhibiting thymidylate
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2 ARC 18~0
synthetase activity. Thymidylate synthetase catalyzes the
methylation of deoxyuridylic acid to thymidylic acid, a DNA
precursor. It also inhibits, to a lesser extent, the formation of
RNA. The effects of DNA and RNA deprivation are most marked on those
s cells which grow more rapidly and which take up fluorouracil at a
more rapid pace.
Fluorouracil is used topically for the treatment of actinic or
solar keratosis and also for the treatment of other tumors of the
skin such as Bowen's disease and superficial basal cell carcinoma
[U.S. Pat. No. 4,849,426; Phvsicians Desk Reference, 43rd Ed.,
Medical Economics Company (1989) p 1729; Martindale, The Extra
Pharmacopoeia, 28th Ed., The Pharmaceutical Press, U.K., (1982)
pp 210-211]. It has also been reported to be useful in the treatment
of psoriasis and other non-malignant skin disorders [U.S. Pat. No.
4,853,388; Pearlman et al. (1986) J. Am. Acad. Dermatol. 15:1247;
Martindale, supra, p 211].
Fluorouracil is available commercially as a 1% topical solution
20 in propylene glycol under the name FLUOROPLEX~ (Herbert Laboratories
dtvision, Allergan Pharmaceuticals). It is also available as a 2% or
5% topical solution in propylene glycol or as a 5% cream under the
name EFUDEX~ (Roche Laboratories division, Hoffmann-La Roche Inc.).
The principal barrier to topical delivery of drugs to the skin
is the stratum corneum, the outermost layer of the skin comprising
keratin-rich cells embedded in multiple lipid bilayers, which
presents a highly impermeable barrier. Such impermeability of the
skin is essential to the well-being of a living organism, preventing
30 ingress of most materials including pharmaceutical agents. Because
of the advantages of dermal application of pharmaceutically active
agents, methods of increasing skin permeability have been sought. In
an effort to increase skin permeability, it has been proposed to use
various penetrating solvents with cytotoxic agents such as 5-
~` 35 fluorouracil, as described in, for example, U.S. 4,820,711, 4,849,426
and 4,853,388, which also cite several other references on the
subject. Examples of such penetration enhancers include, for
,
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3 ARC 1800
example, certain essential oils such as eucalyptus and chenopodium,
substituted azacycloalkan-2-ones such as Azone~ (1-dodecyla~acyclo-
heptan-2-one), bis-azacyclopentanonyl alkanes, dimethylsulfoxide
(DMSO), lower alkyl amides, dimethylacetamide (DMA), dimethyl
s formamide (DMF), 1-methyl-2-pyrrolidone, n-decylmethyl sulfoxide,
propylene glycol, and tertiary amine oxides.
The present invention greatly increases drug permeability
through the skin. While it is known in the art to use permeation
o enhancers singly or together in a binary system in combination with
pharmaceutical agents, this invention utilizes a novel combination of
three enhancers in a permeation-enhancing mixture with a cytotoxic
agent such as 5-fluorouracil. The combined effect produces a
significant improvement.
SUMMARY OF THE INVENTION
The present invention is directed to a composition of matter
for the percutaneous administration of a cytotoxic agent, and
20 particularly to the percutaneous administration of 5-fluorouracil.
The composition comprises, in combination, the cytotoxic agent to be
administered and a permeation-enhancing mixture that includes a lower
alkanol, propylene glycol or a mixture of polyethylene glycols, a
third permeation enhancer and, optionally, a covehicle. The
25 invention is also directed to a method for treating malignant and
non-malignant skin disorders and comprises applying to an area of
skin affected by a skin disorder, a therapeutically effective amount
of the composition of this invention.
BRIEF DESCRIPTION OF THE DRAWIN6S
; FIG. 1 shows the distribution of 5-fluorouracil in epidermis
and dermis of the hairless guinea pig after 24 h permeation from
various permeation-enh~ncing mixtures.
~'. 35
FIG. 2 presents a comparison of 5-fluorouracil distribution
between stratum corneum (SC), epidermis (E) and dermis (D) in
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4 ARC 1800
hairless guinea pig after 24 h permeation from various permeation-
enhancing mixtures.
DETAILED DESCRIPTION OF THE INVENTION
s
This invention codelivers a lower alkanol, propylene glycol or
a mixture of polyethylene glycols, and a third permeation enhancer to
aid in delivery of cytotoxic agents such as 5-fluorouracil across the
skin. Their combined effect according to this invention has been
shown to produce dramatic increases in the permeation of 5-FU
together with a significant reduction on lag time. Improved
enhancement of permeation according to this invention can be obtained
over a relatively wide range of weight ratios.
The present invention, therefore, in one embodiment is directed
to a composition of matter for percutaneous administration of a
cytotoxic agent, the composition comprising, in combination:
a) the cytotoxic agent to be administered; and
b) a permeation-enhancing mixture comprising:
i) a lower alkanol,
ii) propylene glycol or a mixture of polyethylene
glycols,
iii) a third permeation enhancer, and
iv) optionally, a covehicle.
Suitable concentrations of the cytotoxic agent in the
composition will depend upon the choice of agent. When the cytotoxic
agent is 5-fluorouracil, it may be present in the composition in an
amount ranging from about 0.001 to about 10% by weight, preferably
30 from about 0.1 to about 5% by weight, and more preferably from about
0.5 to about 3% by weight. The permeation-enhancing mixture may be
present in an amount ranging from about 90 to about 99.999% by
weight, preferably from about 95 to about 99.9% by weight, and more
preferably from about 97 to about 99.5% by weight.
:`
Suitable cytotoxic agents for use in this invention include
..... ..
ARC 1800
5-fluorouracil, colchicine, vinblastine sulfate, cyclophosphamide,
azathioprine, cyclocytidine, azocytidine, azaserine, cisplatin,
cycloheximide, mechlorethamine, cycloleucine, cytarabine,
dacarbazine, dactinomycin, dichloromethotrexate, emetrine
s hydrochloride, etoposide, quanazole, hydroxyurea, idoxuridine,
mercaptopurine, methotrexate, methyl GAG (methylglyoxal
bis(guanylhydrazone)), metoprine, pyrimethamine, thioguanine,
thiotepa, vincristine sulface, and cyclospor;n A. 5-Fluorouracil is
preferred.
The term, "lower alkanol," as used herein, refers to an alkanol
of two to four carbon atoms. An alkanol of two or three carbons is
preferred, and ethanol is more preferred. The lower alkanol is
present in the permeation-enhancing mixture in an amoun~ of between
about 5% and about 75% by weight, preferably between about 10% and
about 5~% by weight.
The propylene glycol in the permeation-enhancing mixture may be
partially or totally replaced by a mixture of polyethylene glycols of
different molecular weight (from 100 to 10,000) in order to ~odify
the rheology of the formulation. The total amount of propylene
glycol and/or polyethylene glycols present in the permeation-
enhancing mixture is between about 5% and about 75% by weight,
preferably between about 10% and about 50% by weight.
To be considered suitable for use in the present invention as
the third permeation enhancer, an enhancer will be compatible in a
mixture with the lower alkanol and propylene glycol or polyethylene
glycols and in combination will enhance percutaneous penetration of
30 the cytotoxic agent such that the drug delivery rate is at
therapeutic levels. Additionally, the enhancer, when applied to the
skin surface, should be non-toxic, non-irritating on prolonged
exposure and under occlusion, non-sensitizing on repeated exposure .
and essentially free from other adverse side effects. Such a
35 permeation enhancer may be chosen from, but is not limited to,
lactones, particularly butyrolactone; substituted azacycloalkan-2-
ones, particularly those having 5 to 7 carbons in the cycloalkyl
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- -
~3a~9
6 ARC 1800
group such as Azone~; amides such as dimethylacetamide (DMA),dimethyl formamide (DMF) and dimethyl lauramide; propylene carbonate;
polyethylene glycol monolaurate; sorbitan monolaurate; sucrose
monolaurate; sucrose monococoate; pyrrolidones such as octyl
s pyrrolidone; dimethylbutylurea; methyl gluceth-10; glycerol
monooleate; oleic acid; and propionic acid. Preferred as the third
permeation enhancer are propylene carbonate, butyrolactone, sucrose
monolaurate and sucrose monococoate. The third permeation enhancer
is present in the permeation-enhancing mixture in an amount between
about 1% and about 75% by weight, preferably between about 10% and
about 40% by weight.
The covehicle, when present in the permeation-enhancing
mixture, is chosen to be soluble within the enhancer composition.
15 Representative covehicles include water, mineral oil, silicone oil,
ethylene-vinyl acetate polymers or other low molecular weight
polymers soluble in water, lower alcohols or suitable oils.
Preferred are water and mineral oil, with water more preferred. The
covehicle is generally present in the permeation-enhancing mixture in
20 an amount from 0% to about 60% by weight.
The pH of the formulation is conveniently in the range of 2 to
10 and is preferably in the range of 4 to 8. The pH of the
formulation may be adjusted with sodium hydroxide or hydrochloric
25 acid and/or a buffering agent such as, for example, phosphate, TRIS,
HEPES, or EPPS. Thus, where it is necessary to adjust the pH of the
formulation, it is preferred to use an aqueous buffer as the
covehicle.
The present invention greatly increases drug permeability
through the skin. It also significantly reduces the lag time between
application of the drug to the skin and delivery of the drug through
the stratum corneum. These are very desirable attributes because
many cytotoxic agents, such as 5-fluorouracil, are toxic if allowed
35 to remain on the skin surface. Therefore, a short surface exposure
time is better. To obtain a short exposure time while delivering a
therapeutically useful amount of agent, a high flux rate is needed; a
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7 ARC 1800
short lag time is also helpful. As a result, less of the cytotoxic
agent is required to be applied to the treated sites to deliver equal
or greater amounts of drug through the stratum corneum ~nto the
epidermis and especially into the dermis. At the same time, the
s agent is removed quickly from the surface of the skin into the
epidermis and dermis. This, in turn, provides greater efficiency by
using less of the toxic material and also results in less irritation
and other dermatological side effects to the skin during relatively
short exposure (i.e., about one to 24 hours).
- 10
According to the invention, the cytotoxic agent and the
permeation-enhancing mixture are placed in transmitting relationship
to the skin area having the skin disorder, preferably in a
pharmaceutically acceptable carrier therefor. The drug and the
permeation-enhancing mixture are typically dispersed within a
physiologically compatible matrix or carrier which may be applied
directly to the body as a lotion, cream, ointment, gel or solution,
preferably a lotion, cream or solution. Such compositions can also
contain stabilizers, dyes, diluents, pigments, vehicles, inert
20 fillers, excipients, gelling agents, buffers and other components of
topical compositions as is known to the art.
When the composition is applied to the skin, it may be
desirable to occlude the site of administration. Occlusion has been
25 found, in treatment of psoriasis with corticosteroids for example, to
increase the effectiveness of the treatment. However, occlusion of
prior art topical solutions of 5-FU has resulted in reported serious
local toxicities such as erosions and even severe burns. But because
the present invention gives greatly enhanced permeability, less 5-FU
30 iS required in a topical composition, resulting in a much lower and
acceptable degree of local toxicity to the treated site during
relatively short exposure (i.e., about one to 24 hours), whether the
site is occluded or not.
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`' 35In other embodiments, the cytotoxic agent and the permeation-
~~ enhancing mlxture would be administered from a transdermal delivery
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8 ARC 1800
device, such as those described in, for example, U.S. Pat. Nos.
3,598,122, 3,598,123, 4,379,454, 4,286,592, 4,314,557 and 4,568,343.
In the practice of the present invention, the composition
s containing the cytotoxic agent and the permeation-enhancing mixture
is applied to an area of skin having the skin disorder in a quantity
sufficient to wet or cover the surface and to provide a
therapeutically effective amount of the cytotoxic agent to the skin.
By "therapeutically effective amount" is meant an amount of cytotoxic
agent that provides a desired effective therapeutic treatment of the
targeted skin disorder. The treated area may or may not be occluded.
In a preferred embodiment, the treated area is not occluded.
The following examples are offered to illustrate the practice
of the present invention and are not intended to limit the invention
in any manner.
The permeation enhancer/vehicle mixtures used in the following
examples were chosen from those listed in Table A below, to which was
20 added an amount of 5-fluorouracil and trace amounts of radiolabelled
5-FU tavailable from New England Nuclear), to 80% of saturation.
2~38~
9 ARC 1800
TABLE A
% wt/wt Composition
No. Permeation Enhancer PE EtOH ProoYlene G1YCO1 HEPPS*
Control ~ 00
s I Sucrose Monococoate 30 20 20 30
(SMC)
II Sucrose Monococoate 30 20 -- 5
(SMC)
III Propylene Carbonate 30 20 20 30
(PC)
IV Butyrolactone (BL) 30 20 20 30
V Efudex~ -- (absent) (present) ##
VI 5FU/TEA 2/1** ** 22.22 22.22 55.55
* buffer, 0.05 M to pH 6.2
## TRIS buffer to pH 8.9
** molar ratio of 5-FU to triethanolamine
The Efudex~ used in the following examples was a commercial
preparation from Roche consisting of 5% wt/wt fluorouracil compounded .
with propylene glycol, tris(hydroxymethyl) aminomethane,
hydroxypropyl cellulose, parabens (methyl and propyl) and disodium
edetate. The Efudex was labelled with a tracer amount of 3H-5-FU.
EXAMPLE 1
To determine the in vitro permeation of 5-fluorouracil through
human epidermis using various permeation-enhancing mixtures (selected
from Table A), circular pieces (1.63 cm2) of human breast epidermis
were mounted on horizontal permeation cells with the stratum corneum
facing the donor compartment of the cell. A known volume (20-23 ml)
of water (receptor solution) was placed in the receptor compartment.
The cells were then placed in a water bath-shaker at 37-C and allowed
to come to temperature. 0.2 mL of the donor solution (containing 5-
FU at 80% of saturation in the permeation-enhancing mixture) was
transferred to the donor compartment. At 5, 24 and 48 hours, the
receptor solutions were removed and replaced with equal volumes of
j fresh receptor solution previously equilibrated to 37C. To
¦ 40 determine the drug concentration in the removed receptor solutions,
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203~69
ARC 1800
aliquots of the receptor solutions were filtered and weighed inscintillation vials and counted with Aquassure~ scintillation fluor
(New England Nuclear).
s At the end of the permeation tests, the pieces of epidermis
were removed and rinsed once with the corresponding permeation-
enhancing mixture, followed by a rinse in 25% EtOH and two rinses in
water. The epidermis was then blotted between two pieces of filter
paper and weighed in a scintillation vial, digested with NCS
solubilizer and counted with toluene fluor to determine the drug
concentration in the epidermis.
The counts of all the samples and the corresponding specific
activity standards were corrected to disintegrations per minute (DPM)
15 by means of established quench curve programs.
The in vitro flux of 5-FU through human epidermis from each of
formulations I, II, IV and VI was higher than the flux of the drug
from Efudex or from the control. The highest permeation of 5-FU
20 through human epidermis, and also with the shortest lag time, was
obtained from formulat;on I with a drug flux of 1l.9 ~g/cm2-hr at the
5-hr sampling and 14.2 ~g/cm2-hr at the 24-hr sampling. The complete
results are presented in Table B below.
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11 ARC 1800
TABLE B
Donor Soln. Flux ~pidermal
5-FU Conc.* (~q¦cm2-hr) Q** Drug Content
No. (mq/g) 5 hr 24 hr (uq/cm2) (~q/cm2)
Control 15.6 0.160.30 0.82 15.4
I 15.6 11.914.2 332 16.4
o II 14.6 0.905.73 l14 11.2
IV 28.4 1.5312.28 242 69.3
VI 25.2 5.154.11 107 35.7
` .
V Efudex 50.0 0.771.75 38 25.2
* at 80% of saturation
20 ** cumulative amount of drug permeated through epidermis
at 24 hours
EXAMPLE 2
The in vivo permeation of 5-fluorouracil through hairless
guinea pig skin using various permeation-enhancing mixtures (chosen
from Table A) was determined following the procedure described by
Schalla and Schaefer [Localization of compounds in different skin
layers and its use as an indicator of percutaneous absorption. In:
30 Percutaneous absorption: mechanisms. methodoloaY~ drug deliverY.
R.L. Bronaugh and H.I. Maibach, eds., New York: Marcel Dekker Inc.,
(1985)]. Hairless guinea pigs (IAS/HA-H0, Charles River) weighing
450 to 700 g were anesthetized, and the dorsal skin of each animal
was washed with a soap solution, rinsed thoroughly with water and
dried. 10~ ~L of each drug donor solution was applied to 3.63 cm2
sites within glass rings cemented to the dorsal skin. The open end
of the glass ring was sealed with a plastic disc, and the animals
were wrapped with gauze and placed in individual cages with food and
water ad libitum. After 24 hr, the glass ring was removed, the
. 40 excess donor solution was wiped off the skin, and the sites were
`- washed three times with a soap solution. The sites were then rinsed
,,
~` `with water and examined for erythema. The guinea pigs were
sacrificed, and a large piece of skin including the application site
was excised from each guinea pig for stripping and sectioning.
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12 ARC 1800
To remove the stratum corneum by stripping, a piece of adhesive
tape larger than the application site was placed on the skin and a
pressure of 40 g/cm2 was applied over the entire site. The tape was
then "stripped" off with a swift motion. The skin was stripped in
s this way 20 to 25 times to remove as much stratum corneum as
possible. Each piece of tape was incubated 24 h at room temperature
in 15 ml of Aquassure and the radioactive content was measured by
scintillation counting. The full thickness of remaining skin was
then inverted and frozen at -80C. Three punch biopsies 6 mm in
diameter were cut out from each site and each biopsy was frozen and
sectioned parallel to the surface of the epidermis in a cryostat.
Each section was then incubated 24 h in 15 ml of Aquassure and the
radioactive content was measured.
During the above procedure, representative samples of skin
(stripped and normal) were removed and fixed for histology processing
(staining with Masson's trichrome).
Results of 5-FU distribution in tape strips of the stratum
20 corneum are expressed as ~g/cm2, calculated from its known specific
activity. Drug concentrations were not calculated, as the volume of
stratum corneum recovered on each tape could not be determined. In
the epidermis and dermis, 5-FU distribution is expressed as ~g/cm3 of
tissue. Finally, the total quantities of the drug in the stratum
25 corneum, epidermis and dermis are expressed in ~g/cm2. For each
experimental condition, two animals were used (one site per animal).
The stripping was performed on the entire site and the sectioning on
three biopsies of 0.28 cm2. After tape stripping, the guinea pig
skin presented only a few remaining cornified layers at the surface
30 of the epidermis. The epidermis was 30 to 40 ~m thick. The total
thickness of the skin was about 1200 ~m.
The distribution profile of 5-FU in the stratum corneum was
similar with all formulations, although the total amount of 5-FU
35 recovered in the stratum corneum varied from 2.2 + 0.7 ~g/cm2
(formulation II) to 11.7 + 4.1 ~g/cm2 (formulation IV) (Table C).
Differences in the distribution profile were apparent in the
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203896~
13 ARC 1800
epidermis, but these were not statistically significant. In the
dermis, 5-FU concentrations were cons;stently higher after permeation
from formulation I than from the four other formulations. The total
amount of 5-FU recovered in the dermis ranged from 0.9 + 0.1 ~g/cm2
s (formulation V) to 2.9 + 0.8 ~g/cm2 (formulation I) (Table C). See,
also, FIGS. 1 and 2.
TABLE C
10Donor Soln. Total Amount 5-FU Recovered (ug/cm2)
5-FU Conc. Stratum
No. (% wt/wt) Corneum EDidermisDermis
I 1.6 7.6 + 0.1 1.3 + 0.42.9 + 0.8
II 1.6 2.2 + 0.7 0.7 + 0.20.9 + 0.2
III 2.910.6 + 2.1 0.9 + 0.21.4 ~ 0.4
IV 3.111.7 ~ 4.1 1.5 + 0.52.1 + 0.7
- V Efudex 5.03.3 + 1.0 0.6 + 0.20.9 + 0.1
_
Whlle the present invention has been described and illustrated
with reference to certain preferred embodiments thereof, it should
~ not be construed as being limited thereto. Various modifications,
; changes, omissions, and substitutions that are obvious to those of
.~ 30 skill in the art can be effected within the spirit and scope of the
invention and are intended to be within the scope of the following
~, claims.
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