Formulation development and optimization of transungual drug delivery system of terbinafine hydrochloride for the treatment of onychomycosis

The aim of present investigation was to develop transungual drug delivery system (nail lacquer) of terbinafine hydrochloride for treatment of onychomycosis. Different types of penetration enhancers, viz. 2-mercaptoethanol, n-acetyl-l-cysteine and thioglycolic acid, were evaluated to determine their effect on drug permeation. Various types of polymers, both hydrophobic (Eudragit® RL 100 and Eudragit® RS 100) and hydrophilic polymers (hydroxypropyl methyl cellulose (HPMC) E15), were evaluated for their film-forming and drug permeation characteristics. The nail lacquer was optimised statistically by applying 32 full factorial design. Polymer ratio (Eudragit® RL 100/HPMC E15; X1) and solvent ratio (ethanol/water; X2) were selected as independent variable, and viscosity (cPs), nail plate hydration (%) and in vitro drug permeated at the end of 24 h (μg/cm2) were selected as dependent variable. The optimised batch comprises of polymer ratio (70:30) and solvent ratio (75:25). Ex vivo drug permeation study was performed using human cadaver toe nail plate. The results revealed that the amount of drug permeated at the end of 24 h was 61.55 ± 3.2 μg/cm2, which was found to be higher than the minimum inhibitory concentration of drug. This study confirms that the developed drug-loaded nail lacquer could be used as a promising tool for the effective treatment of onychomycosis.