Transdermal delivery of fentanyl: rapid onset of analgesia using skin electroporation.

Skin electroporation has recently been shown to increase transdermal transport of small-size drugs as well as considerably larger molecules by up to 4 orders of magnitude in vitro. Nevertheless, no in vivo studies have proven that high-voltage pulses can induce therapeutic plasma levels of drug. The aim of the present report was precisely to study the potential of skin electroporation in transdermal delivery of fentanyl in vivo. Fentanyl was transdermally delivered to hairless rats using high-voltage pulsing. Following the administration, the pharmacokinetics and pharmacodynamics were assessed. Significant fentanyl plasma concentrations were rapidly achieved using skin electroporation. Immediately after the 5 min pulsing, fentanyl plasma levels reached one third of the maximal plasma concentration of approximately 30 ng/ml, the peak occurring 30 min after the electroporation. Deep analgesia and supraspinal effects were achieved, antinociception lasting for an hour. The magnitude of the effects was, however, dependent on the electrical parameters of the pulses.