Iontophoretic transdermal delivery of ketoprofen: Novel method for the evaluation of plasma drug concentration in cutaneous vein

The objective of our study is to establish a novel method for the in vivo evaluation of transdermal delivery. In this study, cathodal iontophoresis of ketoprofen, a nonsteroidal anti-inflammatory drug, was performed in the thoracic area of rats at a constant direct current, and blood samples were collected from cutaneous vein passing through the thoracic part of the body. After the iontophoresis, the plasma ketoprofen concentration in cutaneous vein ipsilateral to the application site was significantly higher than that in systemic vein. On the other hand, the plasma concentration in cutaneous vein contralateral to the application site was not significantly different from that in systemic vein. A comparison of the time-course curves demonstrated that, for the duration of iontophoresis, the plasma ketoprofen concentration in cutaneous vein ipsilateral to the application site increased with the amount of ketoprofen absorbed in the skin. These results suggest that the plasma concentration in the cutaneous vein ipsilateral to the application site is related with the transfer of drug from skin to cutaneous blood circulation. Therefore, the measurement of plasma concentration in cutaneous vein close to the application site would allow us to directly quantify the local behavior of iontophoretic transdermal absorption.