Although antibiotics have been used for decades to treat acne vulgaris, acne is not a traditional infection. Ozolins and colleagues conducted a randomized controlled trial of five antibiotic regimens for acne vulgaris.

Patients were recruited from a British general practice research network. Criteria for inclusion in the study were mild to moderate acne vulgaris with at least 15 inflamed and 15 noninflamed lesions on the face, no known hypersensitivity to study medications, and willingness to stop all acne therapy for four weeks before the study. Patients with other forms of acne and those whose symptoms began after 26 years of age were excluded from the study. Other exclusions were previous therapy with oral isotretinoin (Accutane), existence of any serious systemic disease, use of any interacting medication, or participation in another clinical trial within the previous three months.

The 649 participants were randomly assigned to one of five antimicrobial regimens: (1) oral oxytetracycline (Terramycin) 500 mg twice daily and topical placebo cream twice daily; (2) oral minocycline (Minocin) 100 mg once daily and topical placebo cream twice daily; (3) oral placebo once daily and topical 5 percent benzoyl peroxide twice daily; (4) oral placebo daily and topical 5 percent benzoyl peroxide plus 3 percent erythromycin (Benzamycin) twice daily; and (5) oral placebo once daily and topical 2 percent erythromycin (T-stat) in the morning and topical 5 percent benzoyl peroxide in the evening. All patients were provided with specific written instructions and nonmedicated soap and moisturizing cream for any local irritation. Adherence was monitored through diaries and return of unused medications. Patients were assessed at baseline and after six, 12, and 18 weeks of therapy. Outcomes monitored were primarily a patient self-assessment using a six-point Likert scale and scoring of acne severity by a trained research assistant. The acne severity score accounted for redness, inflamed lesions, and noninflamed lesions on four areas of the face; and the severity and the number of lesions. Patients also reported quality of life using two standardized questionnaires. The study also monitored skin colonization by antibiotic-resistant propionibacteria.

The patients assigned to either treatment regimen were comparable in all significant variables. Overall, 27 percent of participants did not complete the study. All regimens showed greatest improvement within six weeks (see accompanying table). The two regimens containing topical erythromycin had the highest efficacy, but results were not statistically significant. These two regimens also showed the greatest reduction in propionibacterial activity. The regimen containing minocycline was most compromised by antibiotic resistance. Adverse reactions were noted by 28 percent of participants at week 6, but only 15 percent reported these by week 12. Systemic adverse effects were most common in patients assigned oral antibiotics. The researchers assigned the greatest cost benefit to regimen 3, followed by regimens 5, 1, 4, and 2, in decreasing order. The cost for 18 weeks of therapy ranged from $10.34 to $189.70.

The authors conclude that the five regimens produce similar results but have large differences in cost-effectiveness. Because most benefit occurs within six weeks, the authors suggest limiting the duration of the antibiotics when they prove ineffective after six weeks.