SOME TOPICAL AGENTS FOR MELASMA (PART 1)

28 Aug 2018 NEWS

By causing cosmetic disfigurement of the face, melasma is frequently associated with a significant emotional effect. There is no universally effective specific therapy for the disease—existing agents have varying degrees of effectiveness, and the condition, more often than not, relapses. Most cases are treated with topical agents, used alone, or in combinations. Other modalities of treatment utilized in the management of this hypermelanotic disorder are chemical peels and physical therapies in the form of various lasers or intense pulse light sources. All patients with melasma should be counseled about the natural course of the disease and the necessity for adherence to a long-term treatment plan. Careful history about the possible precipitating or aggravating factors must be taken with special attention to the intake of oral contraceptives or other hormonal preparations, phototoxic and anti-seizure medications, and the usage of cosmetics. Discontinuation of oral pills and avoidance of scented cosmetics is advised. Recurrence of melasma occurs on exposure to sunlight and other sources of ultraviolet rays. Photoprotective measures like the avoidance of direct sun-exposure and the regular use of a broad-spectrum sunscreen are always advised, although clinical studies on their role are lacking. Treatment with demelanizing agents must be continued for several months before significant clinical benefits become noticeable. Topical agents are much more effective in the epidermal type of melasma.

Hydroquinone

Hydroquinone (HQ), also known as dihydroxybenzene, is a hydroxyphenolic compound that is structurally similar to precursors of melanin. It inhibits the conversion of DOPA to melanin by inhibition of the enzyme, tyrosinase. HQ affects not only the formation, melanization, and degradation of melanosomes, but it also affects the membranous structures of melanocytes and eventually causes necrosis of whole melanocytes. HQ is an oxidizing agent that can oxidize in tubes or bottles, turning the color of formulations from white to brown. Products that have undergone this color change are ineffective and should be discarded.

HQ is the most frequently prescribed depigmenting agent worldwide and it has remained the gold standard for the treatment of melasma, particularly of the epidermal type. HQ preparations are commonly used in the treatment of melasma at concentrations varying from 2 to 5% applied once daily. Variably good yet reversible results are obtained in most of the patients treated with HQ. The depigmenting effects of the HQ treatment become evident after 5-7 weeks. Treatment should be continued for at least three months, up to one year. HQ is also formulated in combination with other agents like sunscreens, topical steroids, retinoids, and glycolic acids for added benefits. Adverse reactions of HQ are related to its dose and the duration of treatment. Irritation is the most common complication.

Azelaic acid

Azelaic acid is a naturally occurring, nonphenolic, saturated, nine-carbon dicarboxylic acid that competitively inhibits tyrosinase. Azelaic acid was initially developed as a topical anti-acne agent but because of its effect on tyrosinase, it has also been used to treat hyperpigmentary disorders like melasma. Its mechanisms of action include the inhibition of DNA synthesis and mitochondrial enzymes, thereby inducing direct cytotoxic effects toward the melanocyte. Topical azelaic acid has no depigmentation effect on normally pigmented skin; this specificity may be attributed to its selective effects on abnormal melanocytes. It can be used for postinflammatory hyperpigmentation in acne. Free radicals are believed to contribute to hyperpigmentation, and azelaic acid acts by reducing free radical production.

A double-blind randomized study has shown that a 20% concentration of azelaic acid was equivalent to 4% hydroquinone in the treatment of melasma, but without its side effects. Another controlled study has found azelaic acid to be superior to 2% hydroquinone. A combination of azelaic acid with 0.05% tretinoin or 15-20% glycolic acid may produce earlier, more pronounced skin lightening. Adverse effects of azelaic acid include pruritus, mild erythema, and burning.

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