Open‐label pilot study to evaluate the effectiveness of topical bimatoprost on rhododendrol‐induced refractory leukoderma

Rhododendrol (RD), 4‐(4‐hydroxyphenyl)‐2‐butanol, inhibits melanin synthesis and had been used in skin‐whitening cosmetic products until 2013. However, some individuals developed leukoderma on the skin where RD had been applied and have suffered from refractory depigmentation even after discontinuing RD application. Bimatoprost is a prostaglandin F2α analog and is often used for eyelash growth for cosmetic reasons as well as in the treatment of glaucoma. It was reported that bimatoprost induced skin pigmentation in addition to iris pigmentation as adverse effects. Therefore, we conducted an open‐label single‐center pilot study to evaluate the effectiveness of bimatoprost on refractory RD‐induced leukoderma. Eleven Japanese female patients with skin type III who developed leukoderma on the exact or slightly extended area of skin where RD had been applied and gained a halt of enlargement of leukoderma or repigmentation on a part of the affected skin after discontinuation of RD were enrolled. Bimatoprost 0.03% solution was applied on the leukoderma once daily for 3 months, and then the frequency of application was increased to twice daily for the subsequent 3 months. Ten patients completed the 6‐month course of bimatoprost application. In four patients, bimatoprost application brought slight improvement in RD‐induced refractory leukoderma by dermatologists’ evaluation. Because the number of enrolled patients was limited, further larger studies are necessary to better assess the effectiveness of bimatoprost in inducing repigmentation in patients with RD‐induced refractory leukoderma.