Adapalene gel 0.1% is better tolerated than tretinoin gel 0.025% among healthy volunteers of various ethnic origins

BACKGROUND: The efficacious acne treatment adapalene gel 0.1% is significantly less irritating than tretinoin of various concentrations and formulations, according to several clinical studies conducted predominantly in Caucasian patients. OBJECTIVES: To confirm the lower irritation potential of adapalene gel 0.1% compared to tretinoin gel 0.025% among volunteers of various ethnic origins and to explore the difference in the irritant susceptibility among ethnic groups. METHODS: The study was a single-centre, randomized, investigator-masked and intra-individual comparison. Healthy volunteers applied adapalene and tretinoin daily to the face for 21 days and to the forearms for 4 days, and were then evaluated for the level of irritation. RESULTS: The irritation potential of adapalene gel 0.1% was significantly lower than that of tretinoin gel 0.025% in all tolerability assessments, irrespective of the volunteers' ethnic origins. The between-treatment differences were similar among various ethnic groups. Statistically significant but small inter-ethnicity differences were observed in the evaluation of facial signs, with Caucasians being less susceptible than Chinese, Asian Indians and Malays. CONCLUSION: Adapalene gel 0.1% was significantly better tolerated than tretinoin gel 0.025% among various ethnic groups. The patients' ethnic origins had no impact on the difference between adapalene and tretinoin treatments in terms of tolerability.