Transdermal iontophoretic delivery of selegiline hydrochloride, in vitro

Transdermal iontophoretic delivery of selegiline hydrochloride (SH) across dermatomed human skin was studied. Electrochemical stability and various factors affecting the skin permeation were investigated. SH was stable under the influence of an electrical field. The permeation of SH was very low by passive delivery (2.29 ± 0.05 µg/cm²/h) as compared to iontophoresis at 0.5 mA/cm² (65.10 ± 5.04 µg/cm²/h). An increase in drug concentration from 1 to 20 mg/mL increased the iontophoretic flux by 13-fold. Optimal pH and salt (NaCl) concentration for iontophoretic delivery of SH were found to be pH 5 and 100 mM, respectively. Overall, with 20 mg/mL SH and a current density of 0.4 mA/cm², a maximum flux of 305.5 µg/cm²/h was obtained. Based on reported pharmacokinetic parameters, input target delivery rate to achieve effective plasma concentration of SH (2.2 ng/mL) was calculated. With a surface area of 40 cm², iontophoretic delivery can provide six to seven times higher levels of SH than the target delivery rate, which enables lowering of the dose and/or patch surface area. Further in vivo studies will be required to prove the efficacy of ionophoresis for enhanced delivery of SH.