Compare the Efficacy and Safety Profile of Cysteamine and Hydroquinone in Melasma as Topical Application

Melasma is an acquired pigmentary disorder of symmetrical hyperpigmentation appearing as variable darkness macules and patches over the forehead, cheeks, and chin, even sun-exposed areas of the body. Melasma is predominantly affects women but men can also be affected. Melasma is commonly seen in Asia, where patients with Fitzpatrick skin types III and IV, and areas of high ultraviolet radiation. It is challenging and difficult to treat melasma for its refractory and recurrent nature. There is a variety of therapeutic approaches include topical medication with Kligman's formula, oral medication, chemical peels, lasers, and light therapy.

Cysteamine (b-mercaptoethylamine) hydrochloride is the stable amino-thiol that acts as an antioxidant. It can be naturally produced in the human body and is a degrada-tion product of the amino acid L-cysteine. It has been known to be a potent depigmenting agent for about five decades. The mechanism of cysteamine for depimentation is not through melanotoxicity, which is the major depigmentation mechanism of hydro-quinone. Exogenous ochronsis is the major concern about the long-term use of hydro-quinone. Cysteamine is a thiolic compound that inhibit tyrosinase and peroxidase activity of melanocytes and produce notably greater amounts of pheomelanin but less eumelanin. In addition, thiols can act as a chelating agent of iron and copper ions Fenton reaction during pigment synthesis. Thols can also scavenge dopaquinone and deplete dopaquinone from the melanogenesis pathway. Then, higher levels of intra-cellular glutathione augmented by cysteamine cause the melanogenesis to proceed at a slower rate by shifting eumelanogenesis to pheomelanin synthesis.

Since new technology permits reduction of the sulfur-odour of cysteamine hydro-chloride, cysteamine 5% cream permit the use in topical depigmenting preparations. Considerable efficacy and safety of cysteamine 5% cream in the treatment of epidermal melasma were confirmed by comprehensive measurements in previous well-controlled studies.

However, the depigmenting efficacy of cysteamine compared with hydroquinone has never been evaluated. In addition, durability of the depigmenting efficacy has never been reported and the maintenance usage the cysteamine 5% cream has never yet been studied. In the present study, the investigators evaluate the efficacy of cysteamine 5% cream with hy-droquinone 4% cream in treating melasma and provide the maintenance regimen of cys-teamine 5% cream for Asian patients with melasma.