Background This NHS/HTA-funded study aimed to rank five commonly used antimicrobial therapies for acne in order of their clinical effectiveness and cost-effectiveness. We also wanted to identify which agents are less likely to promote resistance and those which are effective in patients who harbour high numbers of resistant Propionibacterium acnes strains.

Methods From surgeries and colleges in the Nottingham and Leeds areas, 649 patients with mild to moderate facial acne were recruited. The two primary outcome measures were patient self-assessment of improvement in overall acne severity and reduction in inflamed lesion count, measured at 18 weeks. Secondary outcome measures included two acne severity scores, assessors' global estimation of improvement, quality of life and utility scores, enumeration of antibiotic resistant propionibacteria, and the incidence of adverse events.

Results and Conclusions The most effective treatments (percentage with at least moderate improvement according to patients, mean change in lesion count) were the topical Benzamycin® b.d. (66%, − 27) and its components given separately (topical erythromycin o.d. + 5% benzoyl peroxide o.d.) (63%, − 26), followed by 5% benzoyl peroxide b.d. (60%, − 23). The least effective were oral oxytetracycline (55%, − 18) and minocycline (54%, − 22). The most cost-effective treatment was benzoyl peroxide and least cost-effective was minocycline. In terms of quality of life, benzoyl peroxide moved down the rankings and minocycline moved up. The two topical erythromycin-containing regimens produced the largest reductions and the oral treatments the smallest in the prevalence and population density of cutaneous propionibacteria. Prior bacterial colonisation did not affect outcome in the topical groups. Efficacy of both oral preparations was influenced by tetracycline resistant P. acnes strains.

Disclaimer The views and opinions expressed are those of the authors and do not necessarily reflect those of the Department of Health.