Synergy and its clinical relevance in topical acne therapy

Biologically active agents generally are thought of either as acting synergistically (they work together) or antagonistically (they counteract each other). However, the notion of synergy has a more nuanced meaning in pharmacological discussions. Two agents may complement each other, usually by providing a cumulative or additive effect. Within pharmacological discourse, "synergy" indicates that the sum of two agents' combined action is greater than the sum of the efficacy of the constituent parts. An example of synergy in dermatological therapy is a novel fixed combination formulation of adapalene 0.1% and benzoyl peroxide 2.5%. While the use of both topical benzoyl peroxide and a retinoid for the management of mild-to-moderate acne vulgaris has become the standard of care, data show that the two agents in the once-daily, fixed combination adapalene/benzoyl peroxide gel formulation confer a synergistic effect, suggesting that the formulation can enhance efficacy and improve patient convenience and adherence.