All of the agents reviewed have been shown to be effective in the treatment of mild and moderate acne vulgaris. There is very little data to support the use of one agent over another and there has only been one RCT of use of the agents in combination, which showed that benzoyl peroxide and tretinoin in combination are superior to either agent alone.48 Adapalene has been shown to be better tolerated than tretinoin, and the RCT evidence reviewed suggests that azelaic acid may be better tolerated overall than other agents, but there will be considerable variation between individual patients. A number of RCTs compare these agents against and in combination with topical antibiotics; these are considered in the next section.
The role of antibiotics in the management of acne is still debated, and although much evidence has been collected on the efficacy of individual agents, there is very little good-quality comparative data. Oral antibiotics were used initially in the 1950s because it was assumed that acne occurred as a result of bacterial infection. Whilst activity against P. acnes has been clearly demonstrated, there is evidence of an anti-inflammatory effect,80 which is still being investigated.
A number of oral antibiotics have been used to treat acne but are no longer used because of their side-effects; clindamycin and lincomycin are associated with an increased risk of pseudomembranous colitis; dimethylchlortetra-cycline (demeclocycline) induces phototoxic skin reactions and causes dose-dependent nephrogenic diabetes insipidus; and co-trimoxazole is associated with blood dyscrasias. This section therefore focuses on erythromycin, tetracycline, oxytetracycline, minocycline, doxycycline, lymecycline and trimethoprim.
Two systematic reviews provided evidence on the role of antibiotics.14,81 The conclusions of the AHRQ review are based only on comparisons, where there are at least two trials of acceptable quality showing moderate-to-strong statistical evidence for a clinically meaningful endpoint and effect. Of the oral antibiotics, only clear evidence was located for tetracycline. Topical clindamycin and erythromycin were shown to be superior to vehicle in the treatment of mild-to-moderate acne and topical tetracycline was shown to be of no benefit. The Cochrane Review81 of minocycline examined 27 RCTs and concluded that whilst minocycline is likely to produce similar outcomes to other first- and second-generation tetracyclines, it should not be used as a first-line agent because of uncertainty over its safety and higher cost compared with older tetracyclines. There was no evidence to suggest that it is superior to other tetracyclines and its efficacy relative to other acne therapies could not be reliably determined because of inadequacies in the studies examined.
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