Permeability studies of cellulose acetate free films for transdermal use: influence of plasticizers

Permeability of cellulose acetate (CA) free films casted from chloroform solution containing different plasticizers were studied with a view to developing a suitable rate controlling membrane for transdermal use. Dibutyl phthalate (DBP), polyethylene glycol 600 (PEG 600) and propylene glycol (PG) were used as plasticizers at a concentration of 40% w/w of dry polymer weight. The free films were prepared by mercury substrate method and evaluated for uniformity of thickness, tensile strength and percentage elongation and water vapour transmission. Permeability characteristics of free films were studied using the drugs such as diltiazem hydrochloride (DLT) and indomethacin (Ind). The variation in film thickness was less than 2% which ensured uniformity. Tensile strength of films plasticized with DBP is more compared with other plasticized films. Water vapour transmission and drug diffusion through the free films followed zero order kinetics and decreased with increasing the film thickness. The films plasticized with PEG600 showed higher permeability for both drugs compared with other films. The order of decrease of permeability of plasticized films with plasticizers is PEG600 > PG > DBP. Diffusion of drugs through the free films of CA was extended over a longer period of time at a controlled rate and thus, these can be used as rate controlling membranes for the development of a transdermal drug delivery system.