Background  Melasma is associated with epidermal hyperpigmentation, weak basement membrane, vascular proliferation and increased numbers of mast cell. Tranexamic acid (TXA), a plasmin inhibitor, is reported to improve melasma when injected locally. However, the effects of oral and topical TXA on melasma have not been well studied and the underlying mechanism remains unclear.

Objectives  To elucidate the effects of oral and topical TXA on melasma.

Methods  A clinical study was conducted with 25 women for 8 weeks from March to July 2010. Volunteers were instructed to take two TXA tablets three times a day and apply a TXA topical agent twice a day for 8 weeks. Skin pigmentation and erythema was measured using a Mexameter® during each visit and skin biopsies were collected from eight subjects before and 8 weeks after treatment. Fontana-Masson, anti-CD31, antitryptase and antitype IV collagen staining was performed.

Results  Twenty-two subjects completed the study and no serious adverse events occurred during the study period. The mean lesional melanin index (MI) scores decreased significantly. Interestingly, the MI scores for the perilesional skin increased. The erythema index scores of lesional and perilesional skin also showed a similar pattern. Histological analysis showed significant reduction of epidermal pigmentation, vessel numbers and mast cell counts. Type IV collagen staining was not observed in all specimens.

Conclusion  TXA decreased epidermal pigmentation associated with melasma and also reversed melasma-related dermal changes, such as vessel number and increased numbers of mast cells.