Low intrinsic drug activity and dominant vehicle (placebo) effect in the topical treatment of acne vulgaris

Abstract

In drug treatment for acne, topical products alone or in combination with systemic products are commonly prescribed. It was recently pointed out by Chiou that oral tetracyclines, the most commonly prescribed systemic drugs, may not be as effective as commonly assumed because the effect of placebo can approach drug effects during the 4 - 12 weeks of daily administration. The present work evaluated the percent contribution of vehicle (placebo) toward the reported efficacy of reduction in total (inflammatory and non-inflammatory) lesion counts of 8 commonly prescribed topical preparations at the end of 10 - 12 weeks of daily administration. These preparations included 0.1% tretinoin, 0.1% adapalene, 5% dapsone, 1% clindamycin, a combination of benzoyl peroxide with adapalene or clindamycin, and a clindamycin-tretinoin combination. The mean reduction from drugs and vehicles were 42 ± 7.1%, and 23 ± 5.0%, respectively; the mean contribution of vehicle toward drug effect was 55 ± 15% (range 35 - 82%). For 5 benzoyl peroxide preparations evaluated (2 for 2.5%, and 3 for 5.0%), their respective means were 40 ± 9%, and 25 ± 15%, and vehicle-toward-drug contribution was 58 ± 31% (range 9 - 89%). The present work shows the great importance of vehicle effects in topical therapy; in some cases this effect approached 90%. The potential significance of the above findings in the development of more effective topical anti-acne drugs was discussed.