Background and design: --Melasma is a difficult medical problem to treat. Hydroquinone is administered to many patients, but it is unstable and local irritation and dermatitis may develop after a prolonged use at a high concentration. This study introduces a new depigmenting agent, N-acetyl-4-S-cysteaminylphenol, for better management of melanoderma in patients with melasma.
Results: --Our study, based on a retrospective observation of 12 patients using 4% N-acetyl-4-S-cysteaminylphenol in oil-in-water emulsion, showed a complete loss (8%), a marked improvement (66%), or a moderate improvement (25%) of melasma lesions. Visible changes of melanoderma can be seen in 2 to 4 weeks after daily topical application. This depigmentation was associated with a decrease in the number of functioning melanocytes and in the number of melanosomes transferred to keratinocytes. N-acetyl-4-S-cysteaminylphenol is the tyrosinase substrate, and, on exposure to tyrosinase, it formed a melanin-like pigment.
Conclusions: --A phenolic thioether, N-acetyl-4-S-cysteaminylphenol, is a new type of depigmenting agent for the better management of melasma. It is much more stable and less irritating to the skin than hydroquinone, and it is specific to melanin-synthesizing cells.