Comparative irritation potential of two combination acne products: a randomized controlled, subject- and evaluator-blind, comparative study in healthy volunteers.

Background: Two topical 1% clindamycin/5% benzoyl peroxide combination products (BenzaClin [Dermik Laboratories, Inc., Bridgewater, NJ, USA] and Duac [Stiefel Laboratories, Coral Gables, FL, USA]) are commonly used in the treatment of mild-to-moderate acne vulgaris. One adverse event reported with their use is local skin irritation.

Objective: The primary aim of this study was to compare the irritation potential of BenzaClin and Duac using a cumulative irritant patch test on healthy human skin.

Methods: A randomized controlled, subject- and evaluator-blinded design was used to compare the cumulative irritation potential of BenzaClin, Duac, a positive control (0.2% sodium laurilsulfate [SLS]), and a negative control (white petrolatum) in healthy volunteers at a single US research study center. Forty subjects were enrolled and 37 completed the study. Most subjects were women (83%) and Caucasian (68%), and the mean age was 47 years. The 21-day cumulative irritation patch test was used to measure the irritation potential of the products applied under occlusive conditions. Evaluation of dermal reactions to the four products was assessed visually using an ordinal scoring system at the time of removal of each patch. The four patches were applied once daily over 21 days, excluding Saturdays and Sundays, resulting in a total of 15 applications. The primary endpoint, determined prior to data collection, was mean cumulative irritation score at the end of the study on day 22.

Results: At the end of the study, the mean cumulative irritation scores were not significantly different between BenzaClin and Duac (1.39 vs 1.36, respectively; p = 0.668). Both BenzaClin and Duac were significantly more irritating than white petrolatum and significantly less irritating than SLS (both p < 0.001). Based on mean cumulative irritation score, BenzaClin and Duac were classified as moderately irritating, SLS as highly irritating, and white petrolatum as not irritating.

Conclusion: BenzaClin and Duac show similar propensity to cause moderate irritation compared with SLS and white petrolatum when applied to the skin of healthy subjects under occlusive patch conditions.