INTRODUCTION
The use of fixed combinations with benzoyl peroxide (BP) and either a retinoid such as adapalene (adap), or antibacterial such as clindamycin (clin), are commonplace in the management of acne vulgaris (acne). Comparative efficacy data are limited, although in a study of 337 patients with mild-to-moderate acne clin 1.0%-BP 5% (with hydrating excipients) demonstrated a barely statistically significant superiority (P=.046) and more rapid treatment success (P=.035) when compared with adap 0.1%-BP 2.5%.1 In addition, clin 1.0%-BP 5% demonstrated a better tolerability profile, with fewer treatment-related adverse events (AEs).1
Cutaneous safety and tolerability of topical medications has been suggested as a key determinant in patient compliance. A 3-week randomized split-face study in 60 healthy participants to determine the optimal combination of adap and BP regarding irritation potential reported better cutaneous tolerability for adap 0.1%-BP 2.5% than adap 0.1%-BP 5%, and similar profile to BP 2.5% (P=.088) or BP 5% (P=.061) monotherapy. Adap 0.1%-BP 5% induced significantly more irritation than BP 5% monotherapy (P<.001).2
A number of split-face and cumulative irritation studies have demonstrated inferior cutaneous tolerability of adap 0.1%-BP 2.5% to other therapy options in acne patients.3-8 A 2-week single-blind split-face study in 48 patients with mild-to-severe facial acne showed clin 1.0%-BP 5% to have a better tolerability profile to adap 0.1%-BP 2.5% following daily treatment; with irritation, dryness and erythema all significantly less common (P≤.001), and 63% - 64% of patients expressing a preference for the clindamycin combination at week 1 and week 2 respectively.3 Treatment related AEs were significantly less common with clin 1.0%-BP 5%. Pooled results of two single-blind split-face studies enrolling 76 patients with mild-to-moderate acne found clin 1.0%-BP 2.5% to have statistically better tolerability (P<.03) during the first two weeks of treatment when compared with adap 0.1%-2.5%.4
A 2-week randomized, observer-blind, split-face study in acne patients assessed the irritation potential and likelihood of continued use of adap 0.1%-BP 2.5% and clin 1.0%-BP 2.5%. Irritation potential was more pronounced and severe with adap 0.1%-BP 2.5% (P<.05 from day 6). Patients reported clin 1.0%-BP 2.5% was better absorbed, dried more quickly, moisturized/hydrated better, was less likely to sting or burn and left the face smoother/softer.5 A three-week single-blind study assessed the irritation potential of adap 0.1%-BP 2.5% and tretinoin gel microsphere 0.04% in a panel of 170 subjects.8 Tretinoin gel microsphere 0.04% was associated with better facial tolerance with significantly less cumulative erythema, dryness, burning/stinging and itching (all P<.0001).8
Clindamycin 1.0%-benzoyl peroxide 3.75% gel (clin 1.0%-BP 3.75%) has been shown to be effective in moderate to severe acne, with a very low irritation potential.9 The objective of our