Current clinical use of depigmenting agents

A variety of topical depigmenting agents have been used clinically, with varying degrees of success. To date, the most effective topical treatment is a triple-combination agent containing hydroquinone (HQ), tretinoin, and fluocinolone acetonide. However, its use is associated with relatively high frequencies of adverse reactions, and therefore there is a necessity to produce effective topical depigmenting agents with fewer adverse effects. Several processes can be targeted for the treatment of hyperpigmentation; specifically, regulation of melanogenesis by inhibiting tyrosinase activity, a key enzyme in melanin synthesis, represents a major therapeutic target. Another option is regulation of melanosomes by manipulation of their formation or transfer. In addition, depigmenting agents can act through antioxidant or anti-inflammatory activities. We compared the tyrosinase inhibitory activity and cytotoxicity of HQ with those of other cosmetic ingredients. The results showed that although HQ was a strong tyrosinase inhibitor, it was cytotoxic at high concentrations. By contrast, 4-n-butylresorcinol effectively controlled tyrosinase activity without showing toxicity at high concentrations. These findings indicated that 4-n-butylresorcinol had the potential to act as an effective depigmenting agent, while producing less irritation than the currently available agents.