Transungual delivery of terbinafine by iontophoresis in onychomycotic nails

Trans-nail permeability is limited due to the innate nature of the nail plate and the recent investigations indicated the potential of iontophoresis in enhancing the transungual drug delivery in normal nails. However, the onychomycotic nails differ from the normal nails with respect to the anatomical and biological features. The current study investigated the effect of iontophoresis (0.5 mA/cm(2) for 1 h) on the transungual delivery of terbinafine in onychomycotic finger and toe nails. The presence of fungi in the onychomycotic nails was diagnosed by potassium hydroxide (KOH) microscopy. Passive and iontophoretic delivery of terbinafine across the infected nail was studied in Franz diffusion cell. Further, the release profile of terbinafine from the drug-loaded nails was investigated by agar diffusion method. KOH microscopy confirmed the presence of fungi in all the nails used. The amount of drug permeated across the nail plate was enhanced significantly during iontophoresis over passive delivery, that is, by 21-fold in case of finger and 37-fold in case of toe nails. Further, the total drug load in the onychomycotic nail was enhanced by similar to 12-fold (in both finger and toe nails) due to iontophoresis. Release of terbinafine from the iontophoresis-loaded nails into agar plates exhibited two phases, a rapid phase followed by a steady release, which extended >2 months. This study concluded that the drug delivery in onychomycotic nails did not differ significantly when compared with normal nails, although the extent of drug permeation and drug load differs between finger and toe nails.