A double-blind, randomized, bilateral comparison of skin irritancy following application of the combination acne products clindamycin/tretinoin and benzoyl peroxide/adapalene

Background: The use of topical medications for acne vulgaris is often limited by their irritant properties. Newer combination preparations are available and offer convenience, but irritant potential may still be a hindrance, perhaps more so with the combination of 2 agents. Few studies have compared these formulations directly for tolerability. Objective: We sought to compare the tolerability of 2 combination topical acne products, clindamycin 1.2%-tretinoin 0.025% (CLIN/RA) gel and benzoyl peroxide 2.5%-adapalene 0.1% (BPO/ADA) gel. Methods: CLIN/RA and BPO/ADA were applied daily to opposite sides of a subject's face for 21 days in a double-blinded fashion. Investigators' Global Assessments and study subject self-assessments of burning/stinging, itching, erythema, and dryness/scaling were collected. Transepidermal water loss (TEWL) was also measured as an objective measure of skin irritation. A mixed model analysis and repeated-measures analysis of variance were used to compare outcomes for both acne formulations. Results: CLIN/RA produced significantly less burning/stinging than BPO/ADA (P<.001) as well as significantly less pruritus than BPO/ADA (P<.001). BPO/ADA caused significantly more TEWL than CLIN/RA (P=.005). There was no significant difference in the amount of erythema or the amount of dryness/scaling caused by either formulation. Conclusion: CLIN/RA produced significantly less skin irritancy and TEWL than BPO/ADA.