Effect of topical benzoyl peroxide/clindamycin versus topical clindamycin and vehicle in the reduction of Propionibacterium acnes.

Propionibacterium acnes is one of the primary factors involved in the pathogenesis of acne vulgaris; proliferation of this bacteria is present in all patients with inflammatory lesions. Combination topical therapy with agents that have different but complementary antimicrobial mechanisms of action has the potential to increase efficacy and to prevent the emergence of resistant organisms. The onset of action and effectiveness of 3 topical preparations (benzoyl peroxide 5%/clindamycin phosphate 1% gel, clindamycin phosphate 1% solution, and vehicle gel) in reducing P acnes were compared in a randomized, open-label, evaluator-blinded, comparative trial involving 60 healthy volunteers who were free of acne but had high levels of facial P acnes. Treatment with benzoyl peroxide 5%/clindamycin phosphate 1% gel significantly (P<.001) reduced P acnes levels by >1 log10/cm2 from baseline (91% inhibition) 24 hours after application. Progressive declines were observed throughout the 2-week study period, with a 3 log10/cm2 reduction (99.9% inhibition) from baseline in P acnes at the end of the 2-week treatment period. In contrast, significant (P<.05) reductions from baseline in P acnes levels following treatment with clindamycin phosphate 1% solution were only observed at the last assessment period (2 weeks), with an average reduction of 0.64 log10/cm2 (77% inhibition). Patients receiving vehicle gel had no measurable reductions in P acnes from baseline. These results demonstrate that topical benzoyl peroxide 5%/clindamycin phosphate 1% gel produces rapid and clinically relevant reductions in P acnes greater than those produced by single-agent therapy. This activity is likely responsible for the quick onset of clinical efficacy produced by this combination regimen.