INVESTIGATION INTO THE POTENTIAL FOR IONTOPHORESIS FACILITATED TRANSDERMAL DELIVERY OF ACYCLOVIR

The potential for iontophoresis facilitated transdermal transport of acyclovir alone or in combination with a cationic or anionic penetration enhancer (cetrimide or sodium lauryl sulphate respectively) was investigated in the neutral range of the drug (pH 6-8). The amount of drug permeated in vitro across nude mouse skin by means of passive diffusion was low (2.5 mu g/cm(2), 90 min). With iontophoresis treatment the permeation was 3-fold greater than that of passive diffusion when a negative charge was applied to the drug solution, possibly due to some ionisation of the drug. Applying a positive charge increased the iontophoretic permeation slightly over that of passive diffusion due to volume flow. The addition of varying amounts of sodium lauryl sulphate or cetrimide to the donor additionally increased the iontophoretic permeation. A positive donor side was less effective compared with a negative donor mainly due to polarisation during anodal delivery. Cetrimide caused an up to 3-fold higher cathodal permeation of acyclovir compared to sodium lauryl sulphate, largely due to the difference in molecular weight/volume of the permeating ions, but also due to other effects. The increase in permeation with increasing enhancer concentration leveled off at a certain point for both enhancers, possibly due to a change in the zeta potential of the skin.