Post-iontophoresis transport of ibuprofen lysine across rabbit ear skin.

The aim of this work was to study in vitro the post-iontophoresis transport of ibuprofen lysine across rabbit ear skin, from ibuprofen lysine water solutions (20-200 mg/ml and pH 6.8-7.8). Current densities of 0.125, 0.25, and 0.5 mA/cm(2) were applied either continuously or for 15, 30, and 60 min followed by passive diffusion for up to 5h. The results showed a significantly higher cathodal transport compared to passive flux. Anodal iontophoresis also increased ibuprofen permeation, even though the drug is negatively charged. The application of an electric current for a limited period of time, followed by passive diffusion from the reservoir in contact with the skin, produced much higher post-iontophoresis fluxes of ibuprofen than passive diffusion. Post-iontophoresis transport of ibuprofen from lysine salt solutions linearly depended on the total amount of current applied during iontophoresis, and in the absence of background ions was independent of donor drug concentration. The reason for this behavior was the creation of a drug reservoir in the skin owing to the short period of current application.