Comparison of the cumulative irritation potential of adapalene gel and cream with that of erythromycin/tretinoin solution and gel and erythromycin/isotretinoin gel

Background: Adapalene is a naphthoic acid derivative with retinoid activity that is effective in the treatment of mild to moderate acne vulgaris. Objective: This study assessed the cumulative irritation potential of adapa lene gel (0.1%) and adapalene cream (0.1%) compared with that of erythromyc in (4%)/tretinoin (0.025%) solution, erythromycin (4%)/tretinoin (0.025%) g el, erythromycin (2%)/isotretinoin (0.05%) gel, and white petrolatum (negat ive control). Methods: This was a single-center, randomized, controlled, investigator-bli nded. intraindividual comparison study in healthy subjects with normal skin . The cumulative irritation assay (patch test) was used to assess the poten tial for irritation (including erythema) of the treatments. Each subject re ceived all study treatments, randomly applied under occlusion (patch), to s ites on either side of the midline on the mid-thoracic area of the back. Al l patches were applied to the same sites throughout the study, unless the d egree of reaction to the treatment or adhesive necessitated removal. Fur 3 weeks, each test material was applied daily, Monday through Friday, for -24 hours; the Friday patches were left in place over the weekend for -72 hour s. Results: All 36 subjects (26 men. 10 women; age, 18-49 years [mean, 30 year s]) completed the study. In the course of the study, all subjects had great er than or equal to1 application discontinued prematurely on greater than o r equal to1 site due to intolerance. There were no discontinuations with wh ite petrolatum. All erythromycin/tretinoin gel patches were discontinued at day 10; 35 of 36 erythromycin/isotretinoin gel patches were discontinued a t day 9; and 35 of 36 erythromycin/ tretinoin solution patches were discont inued at day 11 or day 17. The adapalene products, although slightly more i rritating (mean cumulative irritation index, 0.25-1) than white petrolatum, were significantly less irritating than the erythromycin/tretinoin and ery thromycin/ isotretinoin products (P < 0.01). Conclusions: Adapalene gel and cream were well tolerated, with possible ben efits for compliance. Their low irritation potential should be considered w hen prescribing a topical retinoid for the treatment of acne vulgaris.