Effect of iontophoresis on in vitro transdermal absorption of almotriptan

The aim of the present work was to characterize the in vitro transdermal absorption of almotriptan through pig ear skin. The passive diffusion of almotriptan malate and its iontophoretic transport were investigated using current densities of 0.25 and 0.50 mA/cm². In vitro iontophoresis experiments were conducted on diffusion cells with an agar bridge without background electrolytes in the donor compartment. Although both current densities applied produced a statistically significant increment with respect to passive permeation of almotriptan (p < 0.01), that of 0.50 mA/cm² proved to be the best experimental condition for increasing the transport of almotriptan across the skin. Under these experimental conditions, the transdermal flux of the drug increased 411-fold with respect to passive diffusion, reaching 264 ± 24 μg/cm² h (mean ± SD). Based on these results, and taking into account the pharmacokinetics of almotriptan, therapeutic drug plasma levels for the management of migraine could be achieved via transdermal iontophoresis using a reasonably sized (around 7.2 cm²) patch.