Twenty three RCTs were identified for the review. Over 7,309 participants were included; the range for intervention groups was from 24 to 2,004. There were 10 RCTs for benzoyl peroxide alone (n=824 participants), 14 RCTs for clindamycin (n=3,143), 15 RCTs for combination benzoyl peroxide/clindamycin (n=1,923), and nine placebo RCTs (n=1,308). None of the four RCTs (n=210) of benzoyl peroxide plus salicylic acid included a placebo arm. All but one RCT used an intention-to-treat analysis; in the remaining RCT, follow-up was only continued for 12 weeks with 38 of 65 participants.
Two to four weeks (early time points):
Indirect comparisons showed greater inflammatory acne lesion reduction for benzoyl peroxide plus salicylic acid ((WMR% 55.2, 95% CI 50.7 to 59.7; four RCTs) compared with the other interventions of benzoyl peroxide/clindamycin (WMR% 40.7, 95% CI 37.2 to 44.2; ten RCTs), benzoyl peroxide alone (WMR% 33.4, 95% CI 29.4 to 37.4%; six RCTs), clindamycin (WMR% 21.5, 95% CI 17.5 to 25.6; five RCTs), or placebo (WMR% 7.3, 95% CI -3.0 to 17.6; three RCTs).
Non-inflammatory acne lesion reduction was also superior for benzoyl peroxide plus salicylic acid (WMR% 42.7, 95% CI 39.3 to 46.1; four RCTs) compared with the other interventions of benzoyl peroxide/clindamycin (WMR% 26.2, 95% CI 22.2 to 30.3; ten RCTs), benzoyl peroxide alone (WMR% 19.1, 95% CI 14.1 to 24.2%; six RCTs), clindamycin (WMR% 10.0%, 95% CI 5.0 to 15.0; five RCTs), and placebo (WMR% 6.7, 95% CI -0.7 to 14.0; three RCTs).
Three interventions (benzoyl peroxide plus salicylic acid, benzoyl peroxide/clindamycin, and benzoyl peroxide) were more effective for both inflammatory and non-inflammatory lesion reduction when indirectly compared with placebo.
10 to 12 weeks (later time points): The results were less clear cut at later time points.
Inflammatory lesion reductions for the interventions of benzoyl peroxide/clindamycin (WMR% 55.6, 95% CI 53.6 to 57.6; 14 RCTs), benzoyl peroxide plus salicylic acid (WMR% 51.8, 95% CI 43.1 to 60.5; two RCTs), benzoyl peroxide alone (WMR% 43.7, 95% CI 41.1 to 46.3; ten RCTs) and clindamycin (WMR% 45.9, 95% CI 42.8 to 49.1; 14 RCTs) were all superior to placebo (WMR% 26.8, 95% CI 21.7 to 31.9; nine RCTs) when compared indirectly. Benzoyl peroxide/clindamycin had the best profile for inflammatory lesion reduction.
Non-inflammatory lesion reduction for the interventions of benzoyl peroxide plus salicylic acid (WMR% 47.8, 95% CI 40.5 to 55.0; two RCTs), benzoyl peroxide/clindamycin (WMR% 40.3%, 95% CI 37.0 to 43.6; 14 RCTs), clindamycin (WMR% 32.6, 95% CI 27.9 to 37.4; 14 RCTs) and benzoyl peroxide alone (WMR% 30.9, 95% CI 25.6 to 36.2; 10 RCTs) were all superior to placebo (WMR% 17.0, 95% CI 11.7 to 22.4; nine RCTs) when compared indirectly. Benzoyl peroxide plus salicylic acid had a better profile than benzoyl peroxide alone and clindamycin; benzoyl peroxide/clindamycin was superior compared with clindamycin, and benzoyl peroxide plus salicylic acid and benzoyl peroxide/clindamycin were similar for non-inflammatory lesion reduction.
Results were also reported for actual lesion counts, which were similar but not identical to those for mean percentage reduction.