Purpose: Transdermal reverse iontophoresis offers a noninvasive tool for clinical and therapeutic monitoring of drugs and endogenous molecules. This study investigated the viability of reverse iontophoresis as an alternative technique to blood sampling for the monitoring of gabapentin.
Methods: Ex vivo studies assessed the influence of polarity, applied current (0.064-0.32 mA) and subdermal concentration (0.5-20 μg/mL) on the recovery of gabapentin. These experiments were carried out in vertical Franz diffusion cell for a period of 3 h using rat skin. In vivo experiments examined the versatility of this method to extract gabapentin from the subdermal region following intravenous administration of gabapentin (30 mg/kg) in rat model.
Results: Preliminary studies demonstrate that greater amount of gabapentin was extracted in the cathodal chamber due to the contribution of electroosmosis. Increasing the current intensity significantly enhances the extraction flux (P < 0.005) and shown linear relation (r(2) = 0.84) between the applied electrical dose (mA*h) and the amount of gabapentin recovered (μg). Indeed, transdermal iontophoresis of gabapentin was found to be concentration dependent in the range studied (0.5-20 μg/mL), which includes clinically relevant level. Further, a linear relationship was established between the iontophoretically recovered gabapentin 3 h flux values and the subdermal concentrations studied. The linear correlation with good regression value (r(2) = 0.92) observed in the in vivo studies infers that the drug in the plasma is proportionally extracted through the skin and potentially represents the subdermal drug concentrations.
Conclusions: Given the promising results, this study concludes that the transdermal reverse iontophoresis technique could be a promising alternative for the noninvasive monitoring of gabapentin.