Two Randomized, Double-Blind, Split-Face Studies to Compare the Irritation Potential of Two Topical Acne Fixed Combinations Over a 21-Day Treatment Period.

Topical therapy of acne vulgaris (acne) is very common, however cutaneous tolerability can influence patient adherence, and concerns about skin irritation have lead to a number of comparative split-face studies. Advances in formulation technology have provided new fixed combinations with lower concentrations of potentially irritating ingredients without compromising efficacy. These developments now afford the opportunity to formulate fixed combinations with higher concentrations of active ingredients that may provide the greater efficacy needed in more severe disease with good tolerability. Here, we compare the tolerability of two such developments, clindamycin-BP 3.75% gel and adapalene 0.3%-BP 2.5% gel, in healthy volunteers with no apparent facial redness or dryness over 21-days, using a split-face methodology. Clindamycin-BP 3.75% gel was more tolerable than adapalene 0.3%-BP 2.5% gel over the duration of the two studies, with statistically significant differences in cumulative change from baseline starting as early as day 4 (stinging), day 5 (erythema, dryness, and scaling), day 6 (burning), and day 8 (itching); and in composite irritation index (stinging, erythema, dryness, scaling, burning, and itching) from day 4. Transepidermal water loss was less with clindamycin-BP 3.75% gel (statistically significant from day 8). Adverse events were twice as common with adapalene 0.3%-BP 2.5% gel. These data suggest that clindamycin-BP 3.75% gel is likely to be better tolerated than adapalene 0.3%-BP 2.5% gel in moderate-to-severe acne. J Drugs Dermatol. 2016;15(6):721-726.