Transdermal delivery of nalbuphine and its prodrugs by electroporation

The aim of this study was to assess the effects of electroporation on transdermal permeation of nalbuphine (NA) and its prodrugs. The permeation characteristics were investigated under various electrical factors and skin barriers to elucidate the mechanisms involved in transdermal delivery of NA and its prodrugs by skin electroporation. The in vitro permeation studies were performed using side-by-side diffusion cells. The various electrical factors investigated were pulse voltage, pulse duration and pulse number; the different skin barriers studied were intact hairless mouse skin, stratum corneum (SC)-stripped skin, delipid skin as well as furry Wistar rat skin. The prodrugs were fully converted to parent drug after skin permeation. Application of electroporation significantly enhanced transdermal permeation of NA and its prodrugs. The enhancement ratios were highest for NA and the four prodrugs showed the similar permeability after electroporation. The permeation amounts of NA and its prodrugs may be increased by application of higher pulse voltage, pulse duration as well as pulse number. Various kinetics and mechanisms were observed for the permeation of the hydrophilic NA and lipophilic nalbuphine enanthate through different skin barriers by applying electroporation. This study demonstrated that electroporation may enhance and control transdermal permeation of NA and its prodrugs. The results also indicated that the physicochemical properties of prodrug had significant effects on kinetics as well as mechanisms of transdermal permeation by electroporation.