Release of nortriptyline hydrochloride from oil-water microemulsions

The release of nortritptyline hydrochloride from oil-in-water (o/w) microem ulsions (isopropyl myristate as oil, propylene glycol as cosurfactant, poly sorbate 80 as surfactant and phosphate buffer. pH 7.4, as the continuous ph ase) containing increasing concentrations of polyethylene glycol 400, used to facilitate the diffusion of a drug from the inner oily phase of the micr oemulsion to the outer aqueous phase of such a dispersion system, was studi ed by deter-mining the permeability constants of the drug through hydrophil ic and lipophilic membranes separating the o/w microemulsions from the rece iving aqueous phase (phosphate buffer pH 7.4). The permeability of nortript yline hydrochloride from microemulsions through the lipophilic membrane inc reased as the concentration of polyethylene glycol 300 in the disperse syst em increased. The apparent permeability constant for nortriptyline hydrochl oride, from the microemulsion without polyethylene glycol, was 1.36 x 10(-3 ) cm h(-1), it increased up to 7.80 x 10(-3) cm.h(-1) in the presence of po lyethylene glycol at a concentration of 50% (v/v) of the initial volume of the aqueous phase.