Objective: To develop a reliable and sensitive high-performance liquid chromatographytandem
mass spectrometry (HPLC-MS/MS) method for the quantification of selegiline in Beagle dog
plasma and apply the validated method to study the pharmacokinetics and bioavailability of oral selegiline
lyophilizate in Beagle dogs.
Methods: Following alkalization with 1 M sodium hydroxide solution, selegiline and the Internal
Standard (IS) zolmitriptan were extracted using tert-butyl methyl ether and separated on a CAPCELL
PAK C18 column under isocratic conditions. They were detected by MS/MS using electrospray ionization
(ESI) in the positive mode. Quantification was performed using multiple reaction monitoring
(MRM) with transitions of m/z 188.05→90.9 for selegiline and m/z 288.05→57.95 for IS.
Results: Calibration curves were constructed in the concentration range of 0.2–200 ng/mL with a lower
limit of quantification (LLOQ) of 0.21 ng/mL. The matrix effect of dog plasma on the selegiline signal
ranged from 98.8 to 105.6%, and the mean extraction recovery ranged from 79.0% to 81.4% at concentrations
of 1.04, 20.8, and 166 ng/mL. The intra-day precision was lower than 6.86% and the inter-day
precisions were lower than 4.63%.
Conclusion: The validation results demonstrated the reliability of this bioanalytical method, which was
successfully applied to study the pharmacokinetics and bioavailability of 1.25 mg of orally administered
selegiline lyophilizate in Beagle dogs. The pharmacokinetic results were also compared with
those obtained following intragastric (i.g.) and intravenous (i.v.) administration. Buccal delivery of
selegiline was found to significantly increase its bioavailability.