Ex vivo Permeation Kinetics of Zidovudine from Pseudolatex Acrylic Film Across Pig Ear Epidermis

The permeation of ionic compounds through lipophilic skin membrane can be enhanced by converting the impermeable ionized drug into a more permeable unionized form with pH-adjusting excipients. The osmotic influx of water into the device core, upon application on the human skin, dissolve the drug and pH-adjusting adjuvant allowing the partitioning and subsequent permeation of unionized drug from the transdermal device core. The present investigation was aimed to evaluate the feasibility of water activated pH-controlled pseudolatex films for transdermal delivery of zidovudine by ex vivo tests. The monolithic pseudolatex transdermal film of zidovudine was prepared by solvent change followed by solvent casting technique using Eudragit RL 100 and Eudragit RS 100 in varying proportions with pH 7.4 in the device core. The prepared films were of desired physicochemical properties. The SEM photomicrographs of drug loaded formulations exhibited uniformity with rough surface and no traces of crack or pores. The ex vivo skin permeation study across pig ear epidermis in Keshary-Chien glass diffusion cell showed that the drug permeability was controlled by the osmotic influx of water into the device core and consequent partition of dissolve drug into and diffusion through the skin. The formulation F2a with 10 % w/w of zidovudine dispersed in the polymer matrix composed of Eudragit RL 100 and Eudragit RS 100 at the ratio of 1:2, respectively, showed nearly the desired flux at 239.09 μg/cm2/h. A patch area of 117.48 cm2 would be required for transdermal delivery of zidovudine to obtain therapeutic plasma concentration at 0.3 μg/ml.