Inhibition of hair growth

Abstract

Mammalian hair growth is reduced by applying to the skin a composition including an inhibitor of an enzyme involved in arachidonic acid metabolism.

Description

[0002] The invention relates to the inhibition of hair growth.

[0003] Arachidonic acid is released from membrane lipids in response to injury or other irritation. The enzyme cyclooxygenase converts arachidonic acid into cyclic endoperoxides commonly known as PGG2 and PGH2. The endoperoxides subsequently are converted into prostoglandins, which are the primary mediators of inflammation in the body.

[0004] The enzyme 5-lipoxygenase converts arachidonic acid into 5-hydroperoxyercosa-6,8,11,14-tetraenoic acid, which subsequently is converted into a family of compounds known as leukotrienes. The exact biological role of leukotrienes has not yet been determined.

[0005] It has now been found that mammalian (including human) hair growth can be inhibited by applying to the skin a composition including an inhibitor of an enzyme involved in arachidonic acid metabolism in an amount effective to reduce hair growth in the applied area. The inhibitor may, for example, be an inhibitor of cyclooxygenase or lipoxygenase, or may inhibit both enzymes.

[0006] Some preferred inhibitors are commonly known as non- steroidal anti-inflammatory drugs (NSAIDs). These drugs include compounds from a variety of chemical classes.

[0007] One preferred class of NSAIDs are propionic acids, which include α-methyl-4-[2-methylpropyl]benzeneacetic acid (ibuprofen), 6-methoxy-α-methyl-2-naphthaleneacetic acid (naproxen), 2-[3-phenoxyphenyl]propionic acid (fenoprofen), 2-[3-benzoylphenyl]propionic acid (ketoprofen), gamma-oxo-[1,1′-biphenyl]-4-butanoic acid (fenoprofen), and 6-chloro-α-methylcarbazole-2-acetic acid (carprofen).

[0008] Another preferred class of NSAIDs are indoleacetic acids, which include 1-[p-chlorobenzoyl]-5-methoxy-2-methylindole-3-acetic acid (indomethacin), 5-fluoro-2-methyl-1-[(4-(methylsulfinyl)phenyl) methylene]-1H-indene-3-acetic acid (sulindac), 1-methyl-5-[p-toluoyl]pyrrole-2-acetic acid (tolmetin), 2-[(2,6-dichlorophenyl)amino]-benzeneacetic acid (diclofenac).

[0009] A third preferred class of NSAIDs are salicylates, which include 2-acetoxybenzoic acid (acetylsalicylic acid) and 5-[2,4-difluorophenyl]salicylic acid (diflunisal).

[0010] A fourth preferred class of NSAIDs are anthranilic acids, which include 2-[(2,6-dichloro-3-methylphenyl) amino]benzoic acid (meclofenamic acid) and 2-[(2,3-dimethylphenyl) amino]benzoic acid (mefenamic acid).

[0011] A fifth preferred class of NSAIDs are enolic acids, such as 4-hydroxy-2-methyl-N-2-pyridinyl-2H-thieno [2,3-e]-1,2-thiazine-3-carboxamide-1,1-dioxide (tenoxicam).

[0012] Other NSAIDs like 4-[6-methoxy-2-naphthyl]-2-butanone (nabumetone) also can be used.

[0013] Examples of other inhibitors that have been found effective in reducing hair growth include quercetin (3,3′,4′,5,7-pentahydroxy flavone), dl-α-tocopherol, apigenin (4′,5,7-trihydroxy flavone), propyl gallate, NDGA (nondihydroguaianetic acid), and caffeic acid (3,4-dihydroxycinnamic acid). All of these compounds are known in the art and are commercially available. Other inhibitors are known in the art; see, for example, Laughton et al., 42 Biochemical Pharmacology 1673 (1991).

[0014] The composition preferably includes a non-toxic dermatologically acceptable vehicle or carrier which is adapted to be spread on the skin. Examples of suitable vehicles are acetone, alcohols, or a cream, lotion, or gel which can effectively deliver the active compound. In addition, a penetration enhancer may be added to the vehicle to further enhance the effectiveness of the formulation.

[0015] The concentration of the inhibitor in the composition may be varied over a wide range up to a saturated solution, preferably from 1 to 30% by weight or even more; the reduction of hair growth increases as the amount of inhibitor applied increases per unit area of skin. The maximum amount effectively applied is limited only by the rate at which the inhibitor penetrates the skin. Generally, the effective amounts range from 100 to 3000 micrograms or more per square centimeter of skin.

[0016] The composition should be applied to the area of the body where it is desired to inhibit hair growth. Typically, the composition can be applied to the face, particularly to the beard area of the face, i.e., the cheek, neck, upper lip, and chin. The composition can also be applied to the legs, arms, torso or armpit. The composition is particularly suitable for the treatment of hirsutism. In humans, the composition should be applied once or twice a day, or even more frequently, for at least three months to achieve a perceived reduction in hair growth.

[0017] Reduction of hair growth is demonstrated when the frequency of hair removal is reduced, or the subject perceives less hair on the treated site, or quantitatively, when the weight of hair removed by shaving (i.e., hair mass) is reduced. Male intact Golden Syrian hamsters are considered acceptable models for human beard hair growth in that they display oval shaped flank organs, one on each side, each about 8 mm. in major diameter, which grow thick black and coarse hair similar to human beard hair. These organs produce hair in response to androgens in the hamster.

[0018] To evaluate the effectiveness of a particular inhibitor in reducing hair growth, the flank organs of each of a group of hamsters are depilated by applying a thioglycolate based chemical depilatory (Surgex). To one organ of each animal 10 μl. of vehicle alone once a day is applied, while to the other organ of each animal an equal amount of vehicle containing the inhibitor is applied. After thirteen applications (one application per day for five days a week), the flank organs are shaved and the amount of recovered hair (hair mass) from each is weighed. Percent-reduction of hair growth is calculated by subtracting the hair mass (mg) value of the test compound treated side from the hair mass value of the vehicle treated side; the delta value obtained is then divided by the hair mass value of the vehicle treated side, and the resultant number is multiplied by 100.

[0019] Some preferred inhibitors were tested according to the above procedure. The results are presented in Table 1; the vehicles used to deliver the inhibitors are reported in Table 2.

TABLE 1
Hair Mass
		Vehi-		Treated	Control	Percent
Compound	Dose	icle	pH	(mg)	(mg)	Inhibition
Propionic
acids
Ibuprofen	20%	B	5.0	1.160 ± .16	1.704 ± .15	30.33 ±
						7.74
Naproxen	20%	A	8.5	0.771 ± .11	2.108 ± .15	62.52 ±
						5.40
Fenoprofen	20%	D	6.0	0.373 ± .10	1.276 ± .11	70.58 ±
						7.04
Ketoprofen	20%	B	4.5	0.895 ± .20	1.293 ± .26	29.70 ±
						5.10
Carprofen	20%	C	6.0	0.776 ± .11	1.274 ± .19	29.69 ±
						11.06
Indoleacetic
acids
Indo-	20%	A	8.0	0.307 ± .08	1.844 ± .28	83.78 ±
methacin						3.66
Sulindac	20%	A	9.0	0.517 ± .09	2.539 ± .27	79.90 ±
						3.27
Tolmetin	20%	A	8.5	1.459 ± .16	2.344 ± .24	37.85 ±
						3.35
Diclofenac	20%	B	8.0	0.648 ± .10	1.769 ± .19	63.40 ±
						5.21
Salicylates
Acetyl-	20%	B	5.0	2.126 ± .33	3.194 ± .21	34.89 ±
salicylic acid						7.91
Diflunisal	20%	D	5.0	0.985 ± .10	1.779 ± .18	38.32 ±
						10.73
Anthranilic
acids
Meclo-	20%	A	8.5	0.719 ± .14	2.144 ± .18	67.77 ±
fenamic acid						4.79
Mefenamic	10%	A	8.8	0.518 ± .13	1.520 ± .11	67.18 ±
acid
						6.03
Enolic acids
Tenoxican	15%	B	8.0	0.326 ± .08	2.116 ± 0.24	85.38 ±
						2.91
Other
Nabumetone	15%	E	6.0	1.267 ± .23	1.684 ± .21	23.23 ±
						10.41
Quercetin	5%	G	6.0	1.100 ± .10	1.543 ± .10	27 ± 6
	10%	E	5.5	0.419 ± .07	2.679 ± .22	83 ± 4
Propyl	5%	B	7.0	0.870 ± .15	2.553 ± .16	67 ± 5
gallate
NDGA	10%	B	6.5	0.450 ± .11	2.391 ± .21	81 ± 4
Caffeic acid	5%	B	6.0	1.740 ± .06	2.424 ± .17	26 ± 5
	15%	H	4.0	0.797 ± .13	2.148 ± .22	62 ± 7

[0020]

TABLE 2
Vehicles Used in Hair Mass Assays
Vehicle A: 68% Purified water, 16% ethanol (200 proof),
           5% propylene glycol, 5% dipropylene glycol,
           4% benzyl alcohol, 2% propylene carbonate.
Vehicle B: 80% Ethanol (190 proof), 17.5% purif:Led
           water, 2% propylene glycol dipelargonate,
           0.5% propylene glycol.
Vehicle C: 30% Dipropylene glycol, 25% acetone, 15%
           ethanol (200 proof), 10% benzyl alcohol, 10%
           dimethyl sulfoxide (DMSO), 10% propylene
           glycol.
Vehicle D: 35% Dipropylene glycol, 30% ethanol (200
           proof), 20% acetone, 10% propylene glycol,
           5% benzyl alcohol.
Vehicle E: 35% Dipropylene glycol, 30% ethanol (200
           proof), 25% acetone, 10% benzyl alcohol.
Vehicle F: 35% Dipropylene glycol, 35% ethanol (200
           proof), 15% acetone, 10% DMSO, 5% benzyl
           alcohol.
Vehicle G: Acetone
Vehicle H: Moisturizing lotion containing common
           cosmetic ingredients which include
           emulsifiers, detergents, and preservatives.

[0021] A preferred inhibitor, indomethacin, was tested for inhibition of hair growth in various formulations. The results are presented in Table 3.

TABLE 3
Hair Growth Inhibition by Indomethacin
in Various Formulations
	Hair Mass
		Treated	Control	Percent
Formulation	pH	(mg)	(mg)	Inhibition
5% in Vehicle A	7.5	1.248 ± .20	2.173 ± .14	43.41 ± 7.75
10% in Vehicle A	7.5	1.084 ± .11	2.364 ± .22	53.32 ± 4.17
15% in Vehicle A	7.5	0.768 ± .10	2.443 ± .15	68.77 ± 3.02
20% in Vehicle A	8.0	0.307 ± .08	1.844 ± .28	83.78 ± 3.66
20% in Vehicle B	7.0	0.261 ± .01	1.653 ± .15	83.37 ± 1.46
10% in Vehicle F	5.5	0.679 ± .08	1.436 ± .20	49.89 ± 5.54
20% in Vehicle F	5.5	0.324 ± .08	1.491 ± .14	78.43 ± 4.39

[0022] It will be appreciated by those skilled in the art that the invention can be performed within a wide range of equivalent parameters of composition and conditions without departing from the spirit or scope of the invention or of any embodiment thereof.

Claims

1. A method of reducing mammalian hair growth, comprising selecting an area of skin on a mammal from which reduced hair growth is desired; and applying to the skin a composition including an inhibitor of an enzyme involved in arachidonic acid metabolism in an amount effective to reduce hair growth.

2. The method of claim 1, wherein the enzyme is selected from the group consisting of cyclooxygenase and lipoxygenase.

3. The method of claim 2, wherein the inhibitor is an inhibitor of cyclooxygenase and lipoxygenase.

4. The method of claim 2, wherein the mammal is a human.

5. The method of claim 3, wherein the mammal is a human.

6. The method of claim 1, wherein said concentration of said inhibitor in said composition is between 1% and 30%.

7. The method of claim 1, wherein the composition is applied to the skin in an amount of from 100 to 3000 micrograms of said inhibitor per square centimeter of skin.

8. The method of claim 1, wherein the composition is applied to an area of skin on the face of a human.

9. The method of claim 1, wherein the area of skin is on the arm of a human.

10. The method of claim 1, wherein the area of skin an on the leg of a human.

11. The method of claim 1, wherein the composition is applied to an area of skin on a human with hirsutism.

12. A method of slowing the growth of body hair, comprising topically applying an effective amount of a compound that inhibits cyclooxygenase and lipoxygenase in an amount effective to reduce skin hair growth.