Effect of Iontophoresis On In-vitro Transdermal Delivery of Tramadol, A Centrally Acting Analgesic

The aim of the present work was to characterize the in vitro transdermal absorption of tramadol hydrochloride (TH) through pig ear skin. Studies of electrical and physicochemical factors acting on the permeation  kinetics of in vitro iontophoresis were performed. Iontophoresis increased the transdermal permeation flux of TH as compared to the diffusion. Increase in applied current density or enhanced the flux of the drug. Continuous current was more potent than pulsed current in promoting TH transdermal permeation. Increasing the frequency or on:off ratio of pulse current induced an enhancement of the flux through the skin. The binary system did not cause an enhancement in the permeation of TH compared to water alone. An increase in donor drug loading dose or increasing the duration of current application resulted in enhancement of the drug flux. Based on these results, and taking into account the pharmacokinetics of TH, therapeutic drug plasma levels could be achieved via transdermal iontophoresis using a reasonably sized (around 20 cm2) patch.