Transdermal iontophoresis of sodium nonivamide acetate. IV. Effect of polymer formulations

The patch or semisolid dosage form is more applicable than solution as a transdermal iontophoretic delivery system to be administered clinically. Therefore the effect of iontophoresis for sodium nonivamide acetate (SNA) from various polymer formulations was investigated by using an in vitro permeation study. The cumulative amount-time curves were suitable to fit by a zero-order equation which indicated a steady-state permeation rate or sustained release effect could be achieved from polymer hydrogels. The permeability coefficient of SNA from polyvinylpyrrolidone (PVP) or hydroxypropylcellulose (HPC) were similar and showed the highest penetration capacity among six individual polymers. In order to develop optimal devices for clinical utilization, blends of two polymers as binary system formulations were prepared in order to attain acceptable bioadhesion and viscosity. The binary cellulose-PVP formulations apparently improve the mechanical characteristics of hydrogel. Moreover, the flux of SNA from these binary systems increased in the order of methylcellulose (MC) + PVP < hydroxypropyl methylcellulose (HPMC) + PVP < HPC + PVP, which was consistent with the rank order of the SNA permeability coefficient from three individual cellulose derivatives. After the examination of pH shift during iontophoresis, HPMC could provide a sufficient buffer capacity to stabilize the pH value of the donor in an electrical field. Isopropyl myristate showed an enhancing iontophoretic flux of SNA after pretreatment with skin, possibly due to the ability of water accumulation in the skin reservoir. However, Atone showed no or negative effect on iontophoretic transport of SNA. (C) 1998 Elsevier Science B.V. All rights reserved.