The AHRQ review located 31 RCTs comparing a topical antibiotic with its vehicle and a further six RCTs were located by independent searches (see Web Table 13.6). Nine of the RCTs also included other comparators. The antibiotics investigated were clindamycin (12 RCTs),58,90,91,114-122 erythromycin (13 RCTs),123-130 erythromycin/zinc (three RCTs),92 131 132 2% fusidic acid (two RCTs),133,134 meclocycline,135 metronidazole,136 triclosan137 and tetracycline (three RCTs).87-89 In the studies for which details were available, all but one study used twice-daily application.58 Many of the studies were underpowered to conclusively state that there were no significant differences between the comparators.
The AHRQ review concluded that although clindamycin tended to produce greater reductions in IL than its vehicle, the results were rarely statistically significant; global measures more consistently indicated superiority to placebo. The evidence available does not support the effectiveness of clindamycin against NIL. Erythromycin similarly had a greater impact on IL. Fusidic acid was shown to be more active than vehicle against IL at 6 weeks in one study but not at 12 weeks in a second study, which also did not show any difference in its activity against NIL. The two meclocycline studies also showed decreases in IL, with no data for NIL. The 0-75% metronidazole RCT showed that it was no more active than placebo in mild-to-moderate acne, neither producing statistically significant reductions in IL or NIL. The three tetracycline RCTs demonstrated that 0-5% tetracycline was approximately 50% more active than vehicle in terms of change in acne grade from baseline, although no intergroup statistical analyses were performed. Only one trial provided data on differential lesion counts; the results suggested that again tetracycline was active against IL but not NIL. In the larger RCTs a 55-60% mean reduction in IL was consistently seen at 12 weeks.14
The AHRQ review located 14 head-to-head trials of topical antibiotics (see Web Table 13.7). There were no differences in efficacy between clindamycin hydrochloride and phosphate,117,118,122 or between different formulations121,138,139 in the six RCTs examined. Four large RCTS132 140-142 and one smaller study143 compared clindamycin and erythromycin; all enrolled subjects had mild-to-severe acne. Several of the trials reported differences between the topical antibiotics for certain outcomes at certain time points, but there were no overall consistent differences. In comparison with tetracycline of unspecified concentration, the two located studies144,145 reported insignificant or inconsistent differences in lesion counts. However, both trials demonstrated a significant difference in favour of clindamycin in the overall measures of acne severity or improvement. No difference between clindamycin and nicotinamide was shown in the RCT located, but it was underpowered to conclusively state equivalence.146
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