Isobutylamido thiazolyl resorcinol for prevention of UVB‐induced hyperpigmentation

Abstract Background Isobutylamido thiazolyl resorcinol (ITR, Thiamidol ® ) has been proposed as a potent tyrosinase inhibitor. A formulation containing ITR has recently shown promising efficacy for the treatment of some hyperpigmentary conditions. Objectives This study aimed to evaluate the efficacy and safety of ITR in the prevention of ultraviolet (UV)‐induced hyperpigmentation in human skin. Materials and Methods We performed a randomized, single‐blinded, pilot study in 30 healthy participants. One arm was randomly assigned to receive an ITR‐containing product for three weeks. Three hyperpigmented spots were induced by UVB irradiation on both arms after 3 weeks of ITR application. Outcome evaluations included measuring mean lightness index (*L) obtained by colorimeter, hyperpigmentation scores by visual analog scale (VAS), and adverse effects. Results Both experimental sides showed no significant difference in terms of skin lightening after ITR application. However, the ITR‐treated sides showed a statistically significant lower mean lightness index compared to control after an induction with UVB. In addition, the ITR‐treated sides had an earlier improvement and resumed the normal skin color after 3 weeks post‐UVB induction. A clinical evaluation by a blinded nontreating physician and subjects was more favorable on the ITR‐treated side than the control side ( P < .05). No significant side effect was noted. Conclusions ITR is an effective agent in the prevention of pigmentary change from UVB irradiation and may serve as a promising agent for preventing other hyperpigmentary conditions.