Skin distribution and pharmaceutical aspects of adapalene gel

Background: The formulation of topical dermatologic products must take into account efficacy, safety, and patient compliance. Objective: We describe how an aqueous gel containing adapalene, a novel naphthoic acid derivative, was selected for the topical treatment of acne. Methods and Results: Dose selection was made using established in vivo models. In the Rhino mouse the comedolytic effect of adapalene 0.1% gel was similar or superior to that of a reference formulation containing 0.025% tretinoin. Qualitative distribution of adapalene after topical application was assessed on cryosections of human skin. They showed rapid penetration of adapalene into the pilosebaceous unit. A liberation/penetration study demonstrated that significant quantities of adapalene were present in epidermis and dermis, but only 0.01% of the applied dose penetrated through the skin. Conclusion: This formulation should result in effective and well-tolerated treatment of acne vulgaris with good patient compliance.