Transdermal Ionotophoretic Delivery of Sufentanil

Iontophoresis promotes the penetration of charged and uncharged molecules through the skin using an electrical current application. In vitro assays were performed to investigate the influence of several electrical and physicochemical parameters on the transdermal permeation of sufentanil. Continuous current application strongly enhanced sufentanil flux through hairless rat skin as compared to passive diffusion. Direct current was more potent than pulse current to promote sufentanil transdermal permeation. An enhancement in current density applied induced an increase in the flux of the drug. When current application was terminated before the end of the experiment, the flux decreased but remained higher than diffusion flux. The pH of the medium affected diffusion and iontophoretic fluxes: in contrast with diffusion, acidic pH was more efficient for iontophoresis. An enhancement of drug concentration enhanced the iontophoretic flux. Application of direct or pulse current induced similar changes in skin permeability to water.