TRANSDERMAL DELIVERY OF SODIUM NONIVAMIDE PROPIONATE BY IONTOPHORESIS

The aim of this study was to investigate the transdermal iontophoresis of a newly designed capsaicin derivative, sodium nonivamide propionat e (SNP), The iontophoretic permeation of SNP from various pH buffers i ncreased following the decrease of pH values. This trend was consisten t with that of sodium nonivamide acetate (SNA) which is another synthe tic analogue of capsaicin, However, the iontophoretic permeability of SNP was much lower than that of SNA, SNP was also delivered iontophore tically from hydrogel formulations. It is suggested that ionizable pol ymers should be avoided for iontophoretic delivery to maintain good pe netration capacity of drugs. Both nonionic cellulose polymers of methy lcellulose (MC) and hydroxypropyl methylcellulose (HPMC) showed higher iontophoretic flux for SNP than the others did. Furthermore, the Bur of SNP leveled off with an increase in the amount of polymers in hydro gel, indicating that the viscosity of vehicles plays an important role in the permeation of SNP, Comparing the various iontophoretic applica tion modes, the discontinuous on/off cyclic mode showed higher penetra tion capacity than did the continuous mode although they possessed the same electrical energy. Moreover, the desorption time of SNP from ski n was approximately 20 min which was longer than that of SNA.