Effect of penetration enhancers on gel formulation of Zidovudine: in vivo and ex vivo studies.

To overcome many challenges associated with antiretroviral drug therapy, novel drug delivery systems present an opportunity for formulation scientists to improve the management of patients with HIV/AIDS. The purpose of this study was to prepare a transdermal delivery system for zidovudine using different penetration enhancers incorporated in carbopol 971P gel and to evaluate the same for rheology, percent drug content, drug deposition, in vitro, ex vivo, and in vivo permeation across rat skin. The rheology studies indicated that 1% w/w carbopol gel had a higher linear viscoelastic region, good creep recovery, and desirable viscosity. Among all gel formulations, gel containing cineole and menthol as penetration enhancers attained a steady-state flux of 5.9 mg/cm(2)/h and 5.4 mg/cm(2)/h of zidovudine, respectively, leading to plasma concentration in the therapeutic range. The drug deposition was also found to be highest in the case of gel containing cineole and menthol as penetration enhancers. The results indicated a linear relationship between in vitro flux and in vivo bioavailability of zidovudine transdermal gel.