Ciclopirox vs amorolfine: in vitro penetration into and permeation through human healthy nails of commercial nail lacquers

One of the pre-requisite for a successful topical antifungal drug indicated for onychomycosis is its bioavailability into the nail unit for achieving fungal eradication and clinical benefit. The aim of this study was to compare in vitro permeation/penetration through and into human nails of amorolfine (MRF) from a 5% anhydrous commercial formulation (Loceryl®) and ciclopirox (CPX) from the 8% aqueous formulation in hydroxypropyl chitosan (HPCH) technology (Onytec®). The ability of the active ingredient to reach efficacious concentrations to inhibit nail pathogens was also evaluated. The amounts of drug permeated and retained in human healthy nails were determined using a suitably modified diffusion apparatus. HPLC analysis of the samples was performed. The HPCH-based CPX formulation demonstrated an efficient penetration into and permeation through the nail plates. Conversely, Loceryl® produced an amount of MRF permeated through and penetrated into the human toenails significantly lower than CPX. The evaluation of the efficacy index showed a higher potential efficacy of Onytec® with respect to Loceryl® on nail pathogens. The present work not only reinforced the previous results on different experimental substrates, but pointed out the superiority of HPCH-based Onytec® formulation containing CPX with respect to Loceryl® commercial product with MRF, both in terms of higher permeation through and penetration into the human nail, and for the efficacy towards the most common ungual pathogens.