AbstractThe aim of the study was to develop hydrogels and investigate the suitability for transdermal delivery of diclofenac sodium (DS) using constant voltage iontophoresis (CVI). Four batches of hydrogels of DS were developed using hydroxylethyl cellulose (HEC) as matrix material and terpenes as penetration enhancers. The hydrogels displayed a viscosity of ~1500 cps at a shear rate of 250 s-1 that was unlikely to change on minute shift in pH or temperature so that the iontophoretic transport would be unaffected. Moreover, the hydrogels were found to possess adequate conductivity at pH 7.4 to enable iontophoretic delivery of DS. In vitro studies indicated that passive transport of DS across porcine skin from hydrogels was comparable (p>0.05) to aqueous solution. The lead hydrogel (F1), containing geraniol was found to enhance the iontophoretic flux of DS by 5.16 fold at 1.5 V compared to passive control. In vivo studies in rats indicated that CVI on application of F1 significantly suppressed (p<0.001) carrageenan induced edema compared to passive treatment throughout the study.