Efficacy and possible mechanisms of topical tranexamic acid in melasma

BACKGROUND: Tranexamic acid (TA) has been suggested as an effective treatment for melasma. AIM: To investigate the effects and mechanism of action of topical TA in the treatment of melasma. METHODS: In this study, 23 participants with melasma applied a 2% TA formulation to the whole face for 12 weeks. Clinical effects were evaluated using the modified Melasma Area and Severity Index (mMASI) and a chromameter. Skin biopsies were obtained from 10 participants to evaluate pigmentation, vascularity and the expression levels of possible paracrine factors contributing to the effect of TA. RESULTS: Most of the participants had mild melasma, with mMASI of < 5. The mMASI scores significantly improved in 22 of 23 participants after application. The L* values were increased and the a* values were decreased in both lesional and perilesional normal skin. Fontana-Masson staining showed a significant decrease in melanin content in the epidermis. The number of CD31-positive vessels and the expression of the vascular endothelial growth factor both tended to decrease. Endothelin (ET)-1 was found to be downregulated with TA. CONCLUSIONS: Topical TA is effective for melasma. This immunohistochemical study found that suppression of ET-1 could be one of the mechanisms of action of TA on melasma.