Cumulative Irritation Potential of Adapalene 0.1% Cream and Gel Compared With Tretinoin Microsphere 0.04% and 0.1%

Despite the many beneficial effects of dermatologic applications, most of the current treatments for acne cause local irritation. The objective of this study was to compare the ability of the epidermis to tolerate adapalene 0.1% cream and gel and tretinoin microsphere in concentrations of 0.04% and 0.1%. A total of 31 subjects were enrolled in the study. The test products were applied under occlusive dressings on the upper back for approximately 24 hours, 4 times a week, and for 72 hours, once a week, for a period of 3 weeks. Skin reactions (erythema score plus other local reactions) at the product application sites were assessed 5 to 30 minutes after dressing removal. Twenty-six subjects completed the study. A total of 10 subjects discontinued use of 1 or more of the test products because of irritation scores reaching severe or greater; all of these discontinuations were at sites treated with the tretinoin products. The mean 21-day cumulative irritancy indices for adapalene 0.1% cream and gel were significantly lower (P,.01) than those for tretinoin microsphere 0.04% and 0.1% and not higher than that of the negative control product.