Electrically-assisted skin delivery of pergolide in vitro: effect of pH, donor concentration and surfactants

The aim of the current study was to identify the variables determining the flux of transdermal iontophoretic delivery of pergolide in vitro and to evaluate the potentials of the delivery design to reach therapeutic plasma concentrations. The effect of: i) pH of donor solution, ii) donor concentration, and iii) the presence of permeation enhancers on pergolide transport were investigated. By reducing the pH in the donor compartment from 5 to 4 no significant difference in the transport rate of pergolide across human stratum corneum was noticed. Furthermore pergolide delivery does not increase linearly with the donor concentration: a further increase in concentration above 100 μg/mL in the donor formulation, did not result in increased transport rates. When the non-ionic surfactant, laureth-3-oxyethylene ether (C12EO3) and propylene glycol (PG) were used in the donor formulation, a significant enhancement by a factor of 2.4 was achieved compared to the control (citrate buffer pH 5). This indicates that the surfactant efficiently enhances the iontophoretic transport of pergolide. In conclusion, these in vitro studies indicate that it could be feasible to reach therapeutic levels by transdermal iontophoresis of pergolide.