Efficacy of Topical Tretinoin and Topical Minoxidil Cotherapy in Androgenetic Alopecia: A Review

Background: Androgenetic alopecia (AGA) frequently occurs in both men and women and is associated with a significant quality-of-life impairment. Topical minoxidil has been demonstrated to have a variable clinical response, and the proposed efficacy of using concomitant topical tretinoin largely stems from increased minoxidil penetration and activation by the follicular sulfotransferase enzyme. Summary: This review summarizes mechanisms, safety, outcomes, and social media perspectives on the subject. Pharmacokinetic evidence demonstrates a nearly threefold increase in systemic absorption when tretinoin cream is applied before minoxidil, with researchers hypothesizing increased permeability as the cause. However, clinical data regarding combination therapy is minimal. One randomized controlled trial reported similar outcomes between dual therapy and topical minoxidil monotherapy; results from smaller investigations, however, are consistent with the potential conversion of some minoxidil nonresponders to responders when tretinoin is used. A social media analysis of 71 online posts was notable for frequently positive claims regarding the interaction, but tolerability concerns were common. Key Messages: Though current evidence does not support the first-line use of dual therapy, topical tretinoin may be considered as an adjunct in AGA, especially in patients without response to topical minoxidil. Any potential benefit, however, should be weighed against the potential for increased irritation.