Pharmacokinetics and relative bioavailability of selegiline in healthy volunteers

Selegiline is beneficial to Parkinsonian patients as an adjunct to levodopa therapy. A sensitive flourimetric assay based on inhibition of rat brain monoamine oxidase-B (MAO-B) in vitro has been developed to study the pharmacokinetics of selegiline. This method quantitates selegiline as low as 0.25 ng ml-1. The pharmacokinetics and relative bioavailability of selegiline were investigated in healthy volunteers following oral administration of 10 mg tablet or solution. A half-life of approximately 70 min was observed following the administration of either dosage form. Although the two dosage forms exhibited a lag time, the absorption was rapid and peak plasma concentrations were observed between 30 and 45 min for the solution and 30 and 90 min for the tablets. Statistically no significant difference was found between Cmax, Tmax, AUC0-infinity and MRT between the two dosage forms. Negligible renal clearance was found in both groups, but apparent oral plasma clearance was comparatively high and indicates rapid elimination of selegiline from the body.