Effective treatment of Parkinson's disease (PD) involves administration of therapeutic agents with complementary mechanisms of action in order to replenish, sustain or substitute endogenous dopamine. The objective of this study was to investigate anodal co-iontophoresis of pramipexole (PRAM; dopamine agonist) and rasagiline (RAS; MAO-B inhibitor) in vitro and in vivo. Passive permeation of PRAM and RAS (20 mM each) across porcine skin after 6 h was 15.7 ± 1.9 and 16.0 ± 2.9 µg/cm2, respectively. Co-iontophoresis at 0.15, 0.3 and 0.5 mA/cm2 resulted in statistically significant increases in delivery of PRAM and RAS; at 0.5 mA/cm2, cumulative permeation of PRAM and RAS was 613.5 ± 114.6 and 441.1 ± 169.2 µg/cm2, respectively - corresponding to 38- and 27-fold increases over passive diffusion. Electromigration was the dominant mechanism for both molecules (>80%) and there was no effect on convective solvent flow. Statistically equivalent delivery was observed with human skin. The co-iontophoretic system showed high delivery efficiency with 29% and 35% of the applied amounts of PRAM and RAS being delivered. Preliminary pharmacokinetics studies in rats confirmed that the input rate in vivo was such that therapeutic amounts of the two drugs could be co-administered to humans by transdermal iontophoresis using reasonably sized patches and moderate current densities.
Keywords: Dopamine agonist; Iontophoresis; MAO-B inhibitor; Patient compliance; Transdermal.
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