TOPICAL PHARMACEUTICAL COMPOSITION OF ACITRETIN
Field of the Invention
The present invention relates to a topical pharmaceutical composition comprising acitretin
and a process for its preparation. It also relates to a method of treating skin disorders by
administering said topical pharmaceutical composition.
Background of the Invention
Psoriasis is a chronic, non-contagious skin disorder. It appears in many different forms
and can affect any part of the body.
Currently, there is no cure for psoriasis. However, over the years a wide variety of topical
and systemic treatment methods that inhibit the inflammation, cell proliferation, or cell
differentiation have been developed. Treatment of psoriasis remains a challenge because of its
chronic recurrent nature. Various topical and systemic therapies include anti-inflammatory
agents, e.g., glucocorticoids; analgesics; chemically synthesized disease-modifying antirheumatic
drugs (DMARDs), e.g., methotrexate, and ciclosporin; antiproliferative agents, e.g., retinoids, and
vitamin D analogs; TNF-a blockers, e.g., etanercept, infliximab, adalimumab, and efalizumab;
monoclonal antibodies against B cells, .e.g., rituximab; T-cell activation blockers, e.g., abatacept;
IL- 1 blockers, e.g., anakinra; coal tar; and phototherapy.
These treatment methods have proven to be of limited value due to disadvantages such as
cosmetic liabilities, severe side effects, high cost, and minimal or short-term efficacy.
Retinoids as an alternative, also known to influence keratinocyte differentiation and have
i proven to be effective in the treatment of variety of keratinization disorders including psoriasis.
I
I U.S. Patent No. 6,353,029 discloses a topical solution composition comprising tretinoin,
I
I 4-hydroxy anisole, polyethylene glycol, antioxidant, chelating agent, a lower alkanol, and water.
U.S. Patent No. 5,643,584 discloses a topical aqueous gel composition comprising
unsolubilized micronized tietinoin particles, a surfactant selected from the group consisting of
octoxynol and nonoxynol, a preservative, a gelling agent, and water.
PC'I' Publication No. WO 90114833 discloses an aqueous gel vehicle for topical
application to the skin comprising active ingredients such as retinoids, in particular tretinoin. The
composition also includes an aqueous medium, a gelling agent, and an antioxidant.
U.S. Patent Nos. 5,914,334 and 6,258,830 disclose topical gel compositions of tazarotene
comprising ~oloxame4r0~7 , polysorbate 40, and hexylene glycol for the treatment of acne and
A review of the prior art thus reveals topical pharmaceutical compositions of retinoids '
such as tretinoin and tazarotene for the treatment of skin disorders such as psoriasis. However,
irritancy to the skin remains the common side effect leading to high level of patient noncompliance.
Acitretin, a metabolite of etretinate, is available as an oral capsule dosage form and is
indicated for the treatment of severe psoriasis. As the use of acitretin is limited by its systemic
side effects, and skin being the target organ for the treatment of psoriasis, there remains an unmet
need for the topical pharmaceutical compositions of acitretin with minimal or no systemic side
effects and with reduced irritancy to the skin.
For a topical pharmaceutical composition, the solubilization and release of a drug from the
composition remains the essential prerequisites to ensure effective treatment. As acitretin is
poorly soluble in water, it remains a great challenge to develop a topical pharmaceutical
composition in which acitretin is maximally solubilized and readily released from the composition
into the skin.
The scientists of the present invention have now developed a topical pharmaceutical
composition of acitretin with acceptable level of efficacy for treating psoriasis and with reduced
irritancy. Further, acitretin is found to be readily released from the composition into the skin.
Also, said composition of the present invention is found to be stable.
Summary of the Invention
The topical pharmaceutical composition of the present invention is a significant advance
over the currently available oral dosage form of acitretin, as there are minimal or no systemic side
effects. Further, the topical pharmaceutical composition of acitretin results in better patient
compliance in comparison to the available oral dosage 'form. In particular, the topical
, pharmaceutical composition of acitretin is in the form of a gel and is found to be stable for at least
three months.
The present invention relates to a topical pharmaceutical composition comprising acitretin
and a process for its preparation. It also relates to a method of treating a skin disorder by
administering said topical pharmaceutical composition.
Brief Description of the Drawings
Figure 1 is a bar chart presentation of mean utriculi size after application of various
strengths of acitretin gels and ~ a z o r a(cta~za rotene) gel.
Figure 2 is a bar chart presentation of percentage reduction in urticuli size after application
of various strengths of acitretin gels and ~azorac@(ta zarotene) gel with respect to control.
Detailed Description of th-e Invention
A first aspect of the present invention provides a stable topical pha'rmaceutical composition
of acitretin comprising a therapeutically effective amount of acitretin and one or more gelling
agents.
According to one embodiment of this aspect, the percentage of gelling agent ranges'fi-om
about 0.05% wlw to about 10% wlw of the composition.
According to another embodiment of this aspect, the gelling agent is a carboxyvinyl
polymer.
According to another embodiment of this aspect, the topical pharmaceutical composition
consists essentially of acitretin as the 'active ingredient, one or more gelling agents to form a gel,
a solvent in which to disperse the gelling agent, and a co-solvent in which to dissolve the acitretin.
Combining the one or more gelling agents and solvent for dispersing the gelling agent with the
solution of acitretinlco-solvent provides a gel of acitretin suitable for topical administration.
The topical pharmaceutical composition may consist essentially of one or more gelling
agents being present at a percentage ranging from about 0.05% wlw to about 10% wlw based on
the total weight of the composition, one or more solvents to disperse the one or more gelling
agents, the acitretin present in an amount of about 0.02% wlw to about 5% wlw based on the total
weight of the composition, and one or more co-solvents to dissolve the acitretin.
According to another embodiment of this aspect, the topical pharmaceutical composition
consists of acitretin as the sole active ingredient, one or more gelling agents to fo& a gel, a solvent
in which to disperse the gelling agent, and a co-solvent in which to dissolve the acitretin.
Combining the one or more gelling agents and solvent for dispersing the gelling agent with the
solution of acitretinlco-solvent provides a gel of acitretin suitable for topical administration.
In one embodiment, the topical pharmaceutical' compositions disclosed herein are
characterized as being unencapsulated.
A second 'aspect of the present invention provides a stable topical pharmaceutical
composition comprising more than about 0.05% wlw of acitretin, wherein the composition has a
mean in-vitro release rate of more than about 10.00 pg/cm2/h" as measured using a Franz diffusion
cell with the conditions of receptor solution comprising isopropyl alcohol and water (60:40, v/v),
membrane supor@ 200, dosage 300 * 30 mg, temperature 32°C * l.O°C.
A third aspect of the present invention provides a process 'for the preparation of a stable
topical pharmaceutical composition of acitretin, wherein the process comprises the steps of: .
(i) dispersing one or more gelling agents in a suitable solvent;
(ii) dispersing/dissolving acitretin and one or more pharmaceutically acceptable
excipients in a suitable co-solvent; and
(iii) mixing the dispersion of step (i) with the dispersion/solution of step (ii) to form a
gel.
A fourth aspect of the present invention provides a method.of treating a skin disorder by
administering a stable topical pharmaceutical composition of acitretin comprising a
therapeutically effective amount of acitretin and one or more gelling agents.
According to one embodiment of this aspect, the skin disorder is selected from the group
comprising psoriasis, keratosis, eczema, rosacea, acne vulgaris, dermatitis, pruritis, seborrhea,
skin cancers, inflammation, and other skin disorders which are responsive to acitretin or etretinate,
and combinations thereof.
I According to another embodiment of this aspect, the skin disorder is psoriasis.
I
1 According to another embodiment of this aspect, the skin disorder is keratosis.
The term "topical," as used herein, refers to a composition meant for application to the
skin, nail, or mucosal tissue.
The term "therapeutically effective amount," as used herein, refers to an amount effective
at dosages and for periods of time necessary to achieve the desired result of treating skin disorders,
in particular psoriasis and keratosis. ,
The term "pharmaceutical' composition," as used herein, refers to gels, solutions,
suspensions, foams, lotions, or sprays. In particular, the pharmaceutical composition of the
present invention is a gel.
The term "acitretin," as used herein, refers to all-trans-9-(4-methoxy-2,3,6-
trimethylphenyl)-3,7-dimethyl-2,4,6,8-nonatetraenoic acid. It fbrther includes its salts,
polymorphs, hydrates, solvates, prodrugs, chelates, or complexes. The topical pharmaceutical
composition of the present invention comprises acitretin in an amount from about 0.005% wlw to
about 10% wlw, in particular from about 0.02% wlw to about 5% w/w based on total weight of
the composition.
The term'"about," as used.herein, refers to any value which lies within the range defined
by a variation of up to +lo% of the value.
The term "stable," as used herein, means not more than 10% w/w of total related
substances are formed on storage at a temperature of 40°C and a relative humidity of 75% or at a
temperature of 25°C and a relative humidity of 60% for a period of at least three months to the
extent necessary for the sale and use of the composition without substantial change in the mean
in-vitro release.rate of acitretin from the composition. The mean in-vitro release rate of acitretin
from the topical pharmaceutical compositions of the present invention upon storage at 40°C/75%
relative humidity (RH) for at least three months is substantially similar to the initial mean in-vitro
release rate of acitretin obtained as soon as practicable after preparation of topical pharmaceutical
compositions.
The term "s~bstantial,'a~s used herein, refers to any value which lies within the range
defined by a variation of up to * 20% of the value.
The term "gelling agent," as used herein, refers to an agent which forms a gel when added
to a suitable solvent. Suitable gelling agents are selected from the group comprising carboxyvinyl
polymers, e.g., carbopolB 980, carbopolB 974P, carbopolB 97 1P , and ~ a r b o p o9l3~4 P; natural
gums, e.g., karaya gum, locust bean gum, guar gum, xanthan gum, arabic gum, tragacanth gum,
carrageenan, pectin, agar, alginic acid, and sodium alginate; cellulose derivatives, e.g.,
hydroxypropyl methyl cellulose, hydroxypropyl cellulose, methylcellulose, hydroxyethyl
cellulose, and sodium carboxymethylcellulose; acrylates, e.g., methacrylates, and polyacrylates;
alginic acid-propylene glycol ester; polyoxyethylene-polyoxypropylene copolymers; polyvinyl
pyrrolidone; polyethylene glycol; polyethylene oxide; polyvinyl alcohol; silicon dioxide; and
mixtures thereof. In particular, thigelling agent used in the topical pharmaceutical composition
of,the present invention is a carboxyvinyl polymer. The topical pharmaceutical composition of
the present invention comprises a gelling agent in an amount of from about 0.05% w/w to about
10% W/W, in particular from about 0.1% w/w to about 5% w/w, based on total weight of the
composition.
Acitretin being poorly insoluble in water, plurality of non-aqueous vehicles as co-solvents
has been used in the present invention to solubilize acitretin. The term "co-solvent," as used
herein, refers to an organic solvent which is used to disperse or dissolve acitretin. Suitable cosolvents
are selected from the group comprising ethers, e.g., diethylene glycol monoethyl ether;
-H Pa 8zBHz 3a-05- zaxg 16 : 35
6
glycols, e.g., propylene glycol, polyethylene glycol, and glycerin; dimethyl isosorbide; fatty acid
esters, e.g., isopropyl myristate, isopropyl palmitate, isopropyl stearate, and ethyl oleate; fatty
acids, e.g., capric acid, lauric acid, myristic acid, oleic acid, and linoleic acid; polyoxyethylene
sorbitan esters, e.g., polysorbate 20, polysorbate 40, polysorbate 60, and polysorbate 80; and
mixtures thereof. Certain water-miscible solvents, e.g., glycerin or propylene glycol, also add
beneficial humectant properties to the composition. The amount of co-solvent used in the present
invention ranges from about 15% wlw to about 45% w/w, more preferably from about 20% wlw
to about 30% wlw based on total weight of the composition. In the present invention, the total
amount of acitretin may be present as solubilized acitretin fraction and remaining as unsolubilized
acitretin fraction.
The selection of co-solvents remains an important factor as it determines the solubility and
release of acitretin from the composition. In a preferred embodiment, the co-solvent is a
combination of diethylene glycol monoethyl ether ,present in a range of about 20% wlw to about
30% wlw, dimethyl isosorbide present in a range of about 1% wlw to about 10% wlw, and
polysorbate 80 present in a range of about 0.1% w/w to about 5% wlw based on total weight of
the composition. The solubility of acitretin increases to approximately 10,000 times in
comparison to solubility in water, when dimethyl isosorbide, diethylene glycol monoethyl ether,
and polysorbate 80 are used in a wlw ratio of about 3.3:24.1: 1. Besides, increasing the solubility
to a remarkable level, the combination of these co-solvents also help to provide the desirable
release of acitretin from the composition into the skin.
The term "solvent," as used herein, refers to a vehicle used to disperse or dissolve.one or
more gelling agents. Suitable solvents are selected from the group comprising water, white soft
paraffin, light liquid paraffin, heavy liquid paraffin, mineral oil, hydrocarbon oil, ester oil,
triglyceride oil, oil of plant origin, oil of animal origin, unsaturated or polyunsaturated oil,
essential oil, silicone oil, and mixtures thereof. In particular, the solvent used in the topical
pharmaceutical composition of the present invention is water.
The topical pharmaceutical composition of the present invention further comprises one or
more pharmaceutically acceptable excipients selected from the group comprising percutaneous
absorption enhancers, antioxidants, preservatives, chelating agents, surfactants, pH-adjusting
agents, humectants, fragrances, and mixtures thereof.
Suitable percutaneous absorption enhancers are selected from the group comprising
sulfoxides, e.g., dimethyl sulfoxide (DMSO); ethers, e.g., diethylene glycol monoethyl ether
(~ranscutol~su);rf actants, e.g., sodium laurate, sodium lauryl sulfate, polysorbate 20, polysorbate
f P G U= -E40L, ~o. ~yso9@ee6g&rid n_dc&io&atq$@;a l@J=glycosides; alcohols, e.g., ethanol, propanol, and h
7
benzyl alcohol; fatty acids, e.g.; lauric acid, oleic acid, valericacid, and isostearic acid;' fatty acid
esters, e.g., isopropyl myristate; and isopropyl palmitate; polyols or esters thereof, e.g., propylene .
glycol, ethylene glycol, glycerol, butanediol, and polyethylene glycol; amides or other nitrogenous
compounds, e.g., urea, dimethyl acetamide, dimethyl formamide, 2-pyrrolidone, 1 -methyl-2-
pyrrolidone, ethanolamine, diethanolamine, and triethanolamine; terpenes; dimethyl isosorbide;
alkanones; and mixtures thereof.
I Suitable antioxidants are selected from the group comprising butylated hydroxy anisole,
butylated hydroxy toluene, sodium mctabisulfitc, ascorbic acid, ascorbyl palmitate, thiourea,
acetylcysteine, dithiothreitol, cysteine hydrochloride, propyl gallate, tert-butyl hydroquinone,
beta-carotene, tocopherols, and mixtures thereof.
Suitable preservatives are selected from the group comprising methyl-, ethyl-, propyl-, or
butyl-esters of hydroxy benzoic acid or sodium salts thereof, benzoic acid, sodium benzoate,
chlorhexedine, benzalkonium chloride, 2-phenoxyethanol, cetrimide, potassium sorbate,
imidurea, dichlorobenzyl alcohol, thiomersal, and mixtures thereof.
Suitable chelating agents are selected from the group comprising ethylenediamine
tetraacetic acid or derivatives or salts thereof, e.g., disodium edetate; dihydroxyethyl glycine;
! glucamine; acids, e.g., citric acid, tartaric acid, gluconic acid, and phosphoric acid; and mixtures
!
I thereof.
Suitable surfactants are selected from the group comprising polyethoxylated fatty acid
esters, polyoxyethylene sorbitan esters, polyoxyethylene hydrogenated castor oil,
polyoxyethylene polyoxypropylene glycol, sorbitan esters, sodium lauryl sulphate, docusate
sodium, nonooxynol, glyceryl monostearate, and mixtures thereof.
Suitable pH-adjusting agents are selected from the group comprising organic or inorganic
acids, e.g., citric acid, acetic acid, fumaric acid, tartaric acid, phosphoric acid, and hydrochloric
acih; organic or inorganic bases, e.g., sodium hydroxide, potassium hydroxide, ammonium
hydroxide, and triethanolamine; and buffers, e.g;, phosphate buffer and acetate buffer. The pH of
the topical pharmaceutical composition of the present invention is adjusted from about 4 to about
7.
Suitable humectants are selected from the group comprising propylene glycol, glycerin,.
butylene glycol, sorbitol, triacetin, and mixtures thereof.
Examples of fragrances include lavender oil,,,rose oil, lemon oil, almond oil, other FDA-
/
approved fragrances, and mixtures thereof.
The compositions of the present invention may further comprise an auxiliary agent, which
. . . . may act as. a cooling agent. Suitable cooling agents are selected from the group. comprising
menth~i,.e.,~ I-.m enthol and dl-menthol; camphor, .e.g., d-camphor and dl-camphor; borneol, e.g ,
-. diborneol .and dl-borneol; and mixtures thereof. Plant oils and extracts containing one or more of
these compounds, e.g., peppermint oil, peppermint extract, camphor tree extract, and lavender
extract may also be used.
The following examples represent various embodiments according to the present
invention. The examples are given solely for the purpose of illustration and are not to be construed
as limitations of the present invention, as many variations thereof are possible without departing
* from the spirit and scope of the invention.
EXAMPLES
Example 1 .
Procedure:
Ingredients
Acitretin
Diethyelene glycol monoethyl ether
Dimethyl isosorbide
Butylated hydroxy anisole
carbopolB 980
Sodium hydroxide solution
Purified water
1. Carbopol@ 980 was dispersed in purified water under stirring.
Quantity (% wlw)
0.20
24.20
3.33
0.05
0.50
q.s.
q.s. to 100.00
2. Acitretin, butylated hydroxy anisole, and dimethyl isosorbide were added into
diethylene glycol monoethyl ether and mixed together.
3. The mixture of step 2 was added into the dispersion of step 1 under stirring.
4. Purified water was added into the dispersion of step 3 to achieve the desired
weight.
5. The pH of the dispersion of step 4 was adjusted to 5 to 6 using sodium hydroxide
solution to form a gel.
Example 2
Procedure:
1. carbopol@ 980 was dispersed in purified water under stirring. .
2. Acih-etin, butylated hydroxy anisole, dimethyl isosorbide, and polysorbate 80 were
added into diethylene glycol monoethyl ether and mixed together.
3. Disodium edetate, sodium benzoate, and ascorbic acid were dissolved into purified
water.
4. The mixture of step 2 was added into the dispersion of step 1.
5. The mixture of step 3 was added into the dispersion of step 4.
6. Purified water was added into the dispersion of step 5 to achieve the desired
weight.
7. The pH of the dispersion of step 6 was adjusted to 5 to 6 using sodium hydroxide
solution to form a gel.
Examples 3-7
Examples 8- 1 3
.
Ingredients
Acitretin
Diethylene glycol
monoethyl ether
Dimethyl isosorbide
Polysorbate 80
Butylated hydroxy
anisole
carbopolB 980
Disodium edeate
Sodium benzoate
Ascorbic acid
Sodium hydroxide
solution
Purified water
Ingredients
Acitretin
Diethylene
glycol
monoethyl ether
Dimethyl
isosorbide
Polysorbate 80
Butylated
hydroxy anisole
CarbopolB 980
Disodium edeate
Sodium
benzoate
Ascorbic acid
Sodium
hydroxide
solution
Purified water
Example
8
0.30
24.10
3.30
1 .OO
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
Example
3
0.02
24.10
3.30
1 .OO
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
Quantity (%
Example
5
0.10
24.10
3.30
1 .OO
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
Example
4
0.05
24.10
3.30
1 .OO
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
Example
9
0.40
24.10
3.30
1 .OO
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
wlw)
Quantity
Example
10
1 .OO
24.10'
3.30
1 .OO
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
Example
6
0.15
Example
7
0.25
(% w/w)
Example
11
0.02
24.28
3.30
1 .OO
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
24.10 24.10
Example
12
0.05
24.25
3.30
1 .OO
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
3.30
1 .OO
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
Example
13
0.10
24.20
3.30
1 .OO
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
-
3.30
1 .OO -
0.05
1.25
0.10
0.20
0.05
q.s.
q.s. to
100.00
Procedure:
1. ~arbo~o9l8@0 w as dispersed in purified water under stirring.
2. Acitretin, butylated hydroxy anisole, dimethyl isosorbide, and polysorbate 80 were
added into diethylene glycol monoethyl ether and mixed together.
3. ' Disodium edetate, sodium benzoate, and ascorbic acid were dissolved into purified
water.
4. The mixture of step 2 was added into the dispersion of step 1.
5. The mixture of step 3 was added into the dispersion of step 4.
6. -Purified water was added into the dispersion of step 5 to achieve the desired
weight.
5. The pH of the dispersion of step 6 was adjusted to 5 to 6 using sodium hydroxide
solution to form a gel.
Solubilitv Studies
The saturation solubility of acitretin was determined by adding excess amount of
acitretin in a conical flask containing a mixture of dimethyl isosorbide, diethylene glycol
monoethyl ether, and polysorbate 80, present in a wlw ratio of 3.3:24.1: 1 .. The mixture was kept
in a shaking water bath for 24 hours at 250C. The saturation solubility of acitretin was measured
to be 2.5 mg/mL by HPLC method [YMC-packB ODs-A column C-18 (150 x 4.6 mm, 5 pm);
mobile phase of methanol:ethanol:glacial acetic acid:water (74:21:5:0.5 v/v/vlv); flow rate of 1.5
mL/min; UV detection at 360 nm]. .
The solubility of acitretin was.found to be 0.7025 mglg of the gel in given compositions
of Examples 5 through 10 containing 0.284 g of a mixture of dimethyl isosorbide, diethylene
glyco'l monoethyl ether, and polysorbate 80, present in a w/w ratio of 3.3:24: 1 : 1. Table 1 gives
the percentage of the acitretin in a solubilized form in acitretin gels prepared as per Examples 2
through 9.
--
as per
- - --
Examples
Stability Data
The gels prepared according to Example 1, Example 2, Example 1 1, Example 12, and
Example 13 were stored at a temperature of 40°C and a relative humidity of 75% RH for a
period of three to six months, and analyzed for acitretin contents by HPLC method [YMC-pack@'
ODs-A column C-18 (150 x 4.6 mm, 5 pm); mobile phase of methano1:ethanol:glacial acetic
acid:water (74:21:5:0.5 v/v/v/v); flow rate of 1.5 mL/min ; UV detection at 360 nm]: The results
of the analysis are represented in Tables 2-4.
Table 2: Results of the Stability Study of the Gel Prepared According to Example 1
Conditions Assay (%)
Related Substances
(40°C/75% RH) (% wlw)'
Initial 101.2 0.14
3 Months 102.6 0.13
Table 3: Results of the Stability Study of the Gel Prepared According to Example 2
Conditions
(40°C/75% RH)
Initial
3 Months
6 Months
Assay (%)
96.6
100.0
100.5 .
Related Substances
(% wlw)
0.17
0.18
0.44
I - Table 4: Results of the Stability Study of the Gel Prepared According to Example 11-13
In-vitro Release Data
An in-vitro release test was performed using a Franz Difhsion Cell having six individual
cells and a supor@ 200 membrane. The receptor solution used was isopropyl alcohol and water .
Related substances
(% wlw)
0.54
0.64
1.03
0.23
0.32
0.73
0.19
0.20
0.48
.Example
11
.
12
13
(60:40, vlv). 300 mg of the gels prepared according to Examples 2 and 5-9 were placed
uniformly on the membrane at a temperature of 32°C * 1 .O°C. The amount of acitretin released
was determined using an HPLC method [20rbaxB column C- 18 (1 50 x 4.6 mm, 5 pm); mobile
- Conditions
(40°C/75% RH)
Initial
3 Months
6 Months
Initial .
3 Months
6 Months
Initial
3 Months
6 Months
phase of buffer:methanol(10:90 vlv); buffer is 20 mM ammonium acetate: acetic acid (1000:30
vlv); flow rate of 0.750 mL/min] and was analyzed using a UV detector at 350 nm. The mean
acitretin release rate at 0 day, 3 months and 6 months at 40°C/7'5% RH from gels prepared as per
Example 2 and 5-9 is given in Table 5.
Assay (%)
. . 101.9
103.8
103.7
97.3
100.0 . .
101.7
97.3,
98.7
101.4
Table 5: Mean In-vitro Release Rate of Acitretin Gels Prepared as per Example 2 and 5-9
From the above table, it is clear that the mean in-vitro release rate of acitretin upon
storage at 40°C/75% RH after 6 months is substantially similar to the initial mean in-vitro
release rate from the control batches.
Example
2
5
6
7
8 . .
9
Rhino Mouse Test
Efficacy Studies
rpa G;$FL,=+Z 3Q - 0 5 - .zg1+=-, 1s 135
14
Mean Release Rate ( p g / ~ m ~ / h ~ ~ ~ )
Initial (Control)
26.16
15.90
19.28
19.87
23.04
28.51
3 Months
(40°C/75% RH) .
25.87
17.26
15.94
15.94 .
21.50
25.01
6 Months
(40°C/75% RH)
24.90
15.66
15.92
18.70 . .
20.35
24.24
Rhino' mouse utriculi reduction assay is a well-characterized animal model for the
evaluation of retinoid'a~tivit(~K ligman and Kligman, "The Effect on Rhino Mouse Skin of
Agents which Influence Keratinizatiori and Exfoliation", J. Invest. Dermatol., 73(5): 354-358,
1979). Rhino mouse skin is characterized by the presence of keratin-containing utricles attached
to the epidermis. The urticle size reduction in rhino mouse can be used to determine the efficacy
of a composition for the treatment of psoriasis (Hsia et al., "Effects of Topically Applied Acitretin
in Reconstructed Human Epidermis and the Rhino Mouse," J. Invest. Dermatol., 128(1): 125- 130,
2008). Acitretin gels of the present invention are compared with commercially available ~ a z o r a c ~
(tazarotene) gel 0.10% wlw indicated for the treatment of psoriasis.
Seven groups were made, each consisting of seven animals as described in Table 6. An
amount of 100 mg * 2% of placebo for acitretin gel, acitretin gels of various strengths, and
reference ~ a z o r a(cta~za rotene) gel 0.10% w/w was applied evenly on the entire dorsal trunk of
the animals with a sterilized spatula/glass rod daily for 14 consecutive days. All the animals from
Group I to Group VII were examined for detailed clinical signs once daily during treatment and
treatment-free period.
Table 6: Study Design for Acitretin Gel for Rhino Mouse Test
After about 72 * 3 hours 01 last application (i.e., day 14), all sulviving ailiillals were
euthanized by cervical dislocation and skin tissue samples (ventral side skin - untreated control
Animal Numbers &
. Sex
1-7
(5 males, 2 females)
8 - 14
(4 males, 3 females)
15 - 21
(4 males, 3 females)
22 - 28
(4 males, 3 females)
29 - 35
(4 males, 3 females)
36 - 42
(4 males, 3 females)
43 - 49
(4 males, 3 females)
site and dorsal side skin - application site) were collected and preserved in 10% neutral buffered.
Concentration
(% wlw)
-
-
0.02
(Example 3)
0.05
(Example 4)
0.10
(Example 5)
0.20
(Example 2)
0.10
Groups
I
I1
I11
IV
V
VI
VII
formalin for histopathology evaluation. In addition to this, some portion of the dorsal side skin
FormulationITreatment
Details
Control
Placebo for acitretin gel
Acitretin gel
Acitretin gel
Acitretin gel
Acitretin gel
~ a z o r a(cta~za rotene) gel
(i.e., application site) from all the animals was also collected in 0.5% vlv acetic acid solution for
whole mount slide preparations and measurement of utriculi diameter. HBa DEh=+T s@,-Gsz- Oi& 16 -- 35
For whole mount preparations, the .skin samples (dorsal side skin, i.e., application site)
were. cut into approximately 1x1 cm2 size and soaked in 0.5% vlv acetic acid solution for
approximately 18 * 1 hour atsa temperature of 2°C to 8°C. The epidermis was carefully peeled
off using a flat-ended spatula/blade/fine forceps and placed on a glass slide with dermal side facing
up, and slides were allowed to air-dry. These tissue slides were later dehydrated by immersing
into ascending grades of isopropyl alcohol (75%, 95%, and 100% for approximately 3 minutes to
5 minutes each), followed by xylene, and mounted. Thk diameter of at least 10 utriculi (2
utriculilfield) was measured by using a ~eica@A'p plication Suite QWin Image Processing and
Analysis Software. Mean utricle diameter was calculated for each animal and subjected for group
mean comparison by using one way analysis of variance (ANOVA) if complied normality test
using D9Agostino Pearson omnibus. As ANOVA results showed significance, Dunnett test was
applied to compare the Group I1 to Group VII withlover untreated control (Group I) and Group
I11 to Group VII withlover placebo (Group I1 ).
The reduction in utriculi diameter was calculated manually based on mean
reduction in the utriculi diameter in different groups with respect to the untreated control (Group
I) and placebo (Group 11) by using the following formula.
Percentage Reduction in utricle diameter
-- Mean Utricle Diameter in Untreated Control or Placebo - Mean Utricle Diameter in Group X x 100
Mean Utricle Diameter in Untreated Control or Placebo
wherein 'X' is the group for which percentage reduction in utricle diameter was calculated.
Table 7 describes the summary of utriculi sizeldiameter after application of various
strengths of acitretin gels and Tazoraca (tazarotene) gel 0.10% wlw. In the untreated control
(Group I) and placebo (Group 11) animals, numerous circular-shaped utriculi were noticed in the
epidermal sheets (whole mount preparation) with an average diameter of 255.38 * 37.16 and
233.61 * 35.41 pm. Application of acitretin gel at all concentrations (0.02% wlw, 0.05% w/w,
0.10% WIW, and 0.20% wlw) produced a significant reduction in the utriculi diameter with an
average diameter of 109.52 * 57.56,60.30 * 6.46,63.64 * 5.19 and 57.46 * 5.65 pm in Group 111,
Group IV, Group V, and Group VI, respectively. Similarly, in Group VII (TazoracB gel 0.10%
wlw), the mean utriculi diameter was reduced up to 45.48 * 7.33 pm. Figure 1 shows the mean
urticuli size after the application of various strengths of acitretin gel and TazoracB (tazarotene) gel
0.10% WIW. Figure 2 shows the percentage reduction in urticuli size after the application of
various strengths of acitretin gel and ~azorac@(ta' zarotene) gel 0.10% wlw with respect to control.
-x p6 D E L H I 30-,35-2 G-% G 3 6 ; z s I
16 I
Table 7: Summary of Utriculi SizeIDiameter
Group I: Untreated Control
Group 11: Placebo for Acitretin Gel - 0%
Group 111: Acitretin Gel - 0.02% wlw
Group IV: ~ci'tretinG el - 0.05% wlw
Group V: Acitretin Gel - 0.10% wlw
Group VI: Acitretin Gel - 0.20% wlw
Group
Mean
DiameterISize
(in microns) * SD
N
% Reduction
with respect to
Control
% Reduction
with respect to
Placebo
. Group VII: Reference Test Item - Tazorac Gel 0.10% wlw.
VI
57.46'
'00
%5.65
7
77.50.
75.20
**Significant at two-sided 1% level of significance; p-value based on Dunnett test for
comparing Groups I1 to VII over Group I (Untreated control).
I
255.38'
zt37.16 '
7
0
-
VII
45.48'
+00
i7.33
7
82.19
80.50
@@ Significant at two-sided 1% level of significance; p-value based on Dunnett test for
comparing Groups I11 to VII over Group I1 (Placebo for acitretin gel).
Percentage' reduction in utricle diameter with respect to control and placebo has been
I1
233.61
*35.41 ,
7
8.53
0
calculated manually as per given formula and not subjected to statistical analysis.
As compared to control and placebo, application of acitretin gel at all concentrations
(0.02% wlw, 0.05% wlw, 0.10% wlw, and 0.20% wlw) significantly reduced the utriculi diameter.
The percentage reduction in the utriculi diameter was not much different within different groups
but acitretin gel at and above 0.05% wlw concentration produced comparable and equivalent
effects with that of ~azorac@ge l 0.10% wlw.
111
109.52'
k57.56
7
57.12
53.10
IV
60.30'
"00
zt6.46
7
76.39
74.30
V
63.64'
"00
zt5.19
7
75.08
72.80
Gross Pathology Studies
At necropsy, mild to moderate-scaling was noticed at application site in some animals in
Group IV (4 of 7 animals), Group V (3 of 7 animals), and Group VI (6 of 7 animals). Whereas,
in Group VII, 3 of 7 animals were found dead and all dead and moribund sacrificed revea-led I
I
reddish discoloration and scaling of skin at application site. Table 8 presents the summary of gross
pathology findings.
Table 8: Summary of Gross Pathology Findings
Reddish discoloration
and scaling - application
NAD - No Abnormality Detected
Histopathological Studies
Histopathology scores were analyzed by using Kruskal-Wallis test followed by Wilcoxon-
Mann-Whitney test for comparison of median histologic scores of Group I1 to VII with/over
untreated control (Group I) and those of Group I11 to VII with/over placebo (Group I1 - Placebo
for Acitretin gel). Further, median histology scores for ventral side skin (untreated control site)
of each group were compared with that of concurrent dorsal side skin (application site) by using
Wilcoxon signed-rank test. All statistical analyses were performed at 5% level of significance
using SAS@ Institute's PC SAS 9.1.3.
As compared to untreated control (Group I) and placebo (Group I1 - placebo for acitretin
gel), the severity of dermal inflammation at site of application (dorsal side skin) revealed was
increased in a concentration dependent manner as given in Table 9. However, more animals
treated with ~azorac@ge l (Group VII) showed comparatively higher dermal inflammation than
that of acitretin gel treated animals.
Table 9: Summary of Histopathology Findings
Groups I I1 I11 IV V VI VII
No. of Animals 7 7 7 7 7 7 7
No. of Dead 0 0 0 0 0 0 3
Groups I I1 I11 IV V VI VII
Dermal Changes: Inflammation
Absent (Grade 0) 6 7 3 1 0 0 1
(85.7) (100.0) (42.9) (14.3) (0.0) (0.0) (14.3)
1
Minimal (Grade 1)
14.3
0 3 3 5 3 2
(0.0) (42.9) (42.9) (7 1.4) (42.9) (28.6)
Mild (Grade 2) 0 0 1 3 2 3 2
(0.0) . (0.0) (14.3) (42.9) (28.6) (42.9) (28.6)
6 Moderate (Grade 3)
O.O
0 0 0 0 1 2
(0.0) (0.0) (0.0) (0.0) (14.3) (28.6)
Figures in parenthesis indicate percent incidence.

WE CLAIM:
1. A stable topical pharmaceutical composition of acitretin comprising a therapeutikally
effective amount of acitretin, a gclling agent, a solvent, and a co~solvent..
2. The stable topical pharmaceutical composition of claim 1, wherein the acitretin is present
in an amount of about 0.02% wlw to about 10% w/w based on total weight of the
composition.
3. A stable topical pharmaceutical composition comprising from about 0.02% wlw to about
0.4% w/w of acitretin based on total weight of the composition, wherein illore than about
15% of the acitretin is present in a solubilized form. ,
4. The stable topical pharmaceutical composition of claim 3 comprising about 0.02% wlw of
acitretin based on total weight of the composition, wherein about 100% of the acitretin is
present in the solubilized form.
5. The stable topical pharmaceutical composition of claim 3 comprising about 0.05% wlw of
acitretin based on total weight of the composition, wherein about 100% of the acitretin is
present in the solubilized form.
6. The stable topical pharmaceutical composition of claim 3 comprising about 0.1% wlw of
acitretin based on total weight of the composition, wherein about 70% of the acitretin is
present in the solubilized form.
7. The stable topical pharmaceutical composition of claim 3 comprising about 0.2% w/w of
acitretin based on total weight of the composition, wherein about 35% of the acitretin is
present in the solubilized form.
8. The stable topical pharmaceutical composition of claim 3, wherein the composition is a
gel.
9.. The stable topical pharmaceutical composition of claim 3, wherein the composition
comprises a gelling agent, a solvent, and a co-solvent.
10. The stable topical pharmaceutical composition of claims 1 or 3, wherein the percentage of
the gelling agent ranges. from about 0.05% w/w to about 10% wlw based on total weight
of the composition.
1 1. The stable topical pharmaceutical composition of claims 1 or 3, wherein the gelling agent
is selected from the group comprising carboxyvinyl polymers, natural gums, cellulose
derivatives, acrylates, alginic acid-propylene glycol ester, polyoxyethylenepolyoxypropylene
copolymers, polyvinyl pyrrolidone, polyethylene glycol, polyethylene
oxide, polyvinyl alcohol, silicon dioxide, and mixtures thereof. .
12. The stable topical pharmaceutical composition of claim 11, wherein the gelling agent is a
carboxyvinyl polymer.
13. The stable topical pharmaceutical composition of claims 1 or 3, wherein the solvent is
selected from the group comprising water, white soft paraffin, light liquid paraffin, heavy
liquid paraffin, mineral oil, hydrocarbon oil, ester oil, triglyceride oil, oil of plant origin,
oil of animal origin, unsaturated or polyunsaturated oil, essential oil, silicone oil, and
mixtures thereof.
14. The stable topical pharmaceutical composition of claim 13, wherein the solvent is water.
15. The stable topical pharmaceutical composition of claims 1 or 3, wherein the co-solvent is
selected from the group comprising ethers, glycols, diniethyl isosorbide, fatty acid esters,
fatty acids, polyoxyethylene sorbitan esters, and mixtures thereof.
16. The stable topical pharmaceutical .composition of claim 15, wherein the co-solvent is
diethylene glycdl monoethyl ether.
17. The stable topical pharmaceutical composition of claim 15, wherein the co-solvent is
. . dimethyl'isosorbide.
18. The stable topical pharmaceutical composition of 'claim 15, wherein the co-solvent is
polysorbate 80.
19. The stable topical pharmaceutical composition of claim 15, wherein the co-solvent is a
combination of diethylene glycol monoethyl ether, dimethyl isosorbide; and polysorbate
80.
20. The stable topical pharmaceutical composition of claim 19, wherein diethylene glycol
monoethyl ether is present in a range of about 20% to about 30% wlw based on total weight
, of the composition.
2 1. The stable topical pharmaceutical composition of claim 19, wherein dimethyl isosorbide
is present in a range of about 1% to about 10% wlw based on total weight of the
composition.
22. The stable topical pharmaceutical composition of claim 19, wherein polysorbate 80 is
present in a range of about 0.1 % to about 5% w/w based on total weight of the composition.
'23. The stable topical pharmaceutical composition of any of preceding claims, wherein the
composition further comprises one or more pharmaceutically acceptable excipients
selected from the group comprising percutaneous absorption enhancers, antioxidants,
preservatives, chelating agents, surfactants, pH-adjusting agents, humectants, fragrances,
and mixtures thereof.
24. The stable topical pharmaceutical composition of any of preceding claims, wherein the
composition has a pH from about 4 to about 7. jFp-6 Q-ELHz Ta - 0 5 - PGig - l g :
2 1
25. A stable topical pharmaceutical composition .comprising at least about 0.05% wlw of
acitretin,based on total weight of the composition, wherein the composition has a mean invitro
release rate of more than about 10.00 pg/cm2/h"2 as measured using a Franz diffusion
cell with the conditions of receptor solution comprising isopropyl alcohol and water
(60:40, v/v), membrane ~upor@200d,o sage 300 * 30 mg, temperature 32OC * 1. O°C.
26. A stable topical pharmaceutical composition effective for treating psoriasis comprising
from about 0.05% w/w to about 0.2% w/w of acitretin based on total weight of the
composition, wherein a percentage reduction in utriculi size is comparable to ~azorac@'
0.1% gel using a Rhino Mouse Model.
27. A stable topical pharmaceutical composition'effective for treating psoriasis comprising
from about 0.02% w/w to about 0.2% w/w of acitretin based on total weight of the
composition, wherein the composition exhibits reduced skin irritancy in comparison to
' ~ a z o r a0c.1~% gel using a Rhino Mouse Model. +
28. The stable topical pharmaceutical composition of claims 1, 3, or 25, wherein the
composition is administered for treating a skin disorder selected from the group
,- comprising psoriasis, keratosis, eczema, rosacea, acne vulgaris, dermatitis, pruritus,
seborrhea, skin cancers, inflammation, other skin disorders which are responsive to
acitretin or etretinate, and combinations thereof.