Different physicochemical properties of antimycotic agents are relevant for penetration into and through human nails.

This article reports the characterization of the physicochemical properties of two important antifungal topical drugs, amorolfine and ciclopirox. Furthermore, the release of the drugs from commercial lacquer formulations for treatment of onychomycosis was studied using the online FTIR-ATR technique. Based on the physicochemical background of these two drugs and their release from commercial lacquer formulations for treatment of onychomycosis, the suitability of these drugs for optimized local antifungal therapy to human nails is discussed. Amorolfine appears to be more suitable for drug delivery to human nails because it penetrates into the nails via the hydrophilic pathway. Furthermore amorolfine penetrates very well into fungal cells, due to the pH value of the nail, as well as the pK a value of this antimycotic agent and the lipophilic properties of its base form.