The present study aimed to develop bilayered nail lacquer of terbinafine hydrochloride (TH) for treatment of onychomycosis. The composite nail lacquer formed an underlying drug-loaded hydrophilic layer and overlying hydrophobic vinyl layer. The hydrophilic lacquer made of hydroxylpropyl methylcellulose E-15 contained polyethylene glycol 400 (PEG 400) as a drug permeation enhancer. The vinyl lacquer was composed of poly (4-vinyl phenol) as a water-resistant film former. In vitro permeation studies in Franz diffusion cells indicated that the amount of TH permeated across the human cadaver nail in 6 days was 0.32 +/- 0.14, 1.12 +/- 0.42, and 1.42 +/- 0.53 microg/cm(2) from control (hydrophilic lacquer devoid of PEG 400), monolayer (hydrophilic lacquer alone), and bilayered nail lacquers, respectively. A higher nail drug load was seen in vitro with the bilayered lacquer (0.59 +/- 0.13 microg/mg) as compared to monolayer (0.36 +/- 0.09 microg/mg) and control (0.28 +/- 0.07 microg/mg) lacquers. The drug loss despite multiple washing was significantly low (p < 0.001) for the bilayered lacquer owing to the protective vinyl coating. Clinical studies demonstrated the efficacy of bilayered lacquer to achieve better drug load in the nail plate (1.27 +/- 0.184 microg/mg) compared to monolayer (0.67 +/- 0.18 microg/mg) and control (0.21 +/- 0.04 microg/mg) lacquers.