LC–ESI/MS Analysis of Levodopa and Methyldopa (IS) in Beagle Dog Pharmacokinetic Study after Oral Administration and Domperidone Given in Advance

Abstract

AbstractA simple, sensitive and accurate method was developed for the quantification of levodopa and methyldopa (IS) in beagle dog plasma by LC–ESI/MS, chromatographic separation was carried out by a Diamonsil C18 column (150 mm × 4.6 mm i.d., 5 mm) with an ODS guard column maintained at 30 °C. The mobile phase was methanol (A) and 0.5% formic acid aqueous solution (B) system in the gradient elution profile, the retention time of levodopa and IS were 4.8 and 6.1 min, respectively, linear range for levodopa concentration was 0.08‐20.0 μg/mL in plasma samples with a correlation coefficient(r) of 0.9978, the limit of detection was 32 ng/mL. CV of intra‐day and inter‐day assays were all less than 15%, mean recoveries of levodopa were all more than 90% in 0.32, 1.6 and 16.0 μg/mL concentrations of levodopa (n = 3). The validated method was successfully applied to the determination of levodopa in plasma samples, pharmacokinetic of levodopa following a single oral dose of compound levodopa tablets and antiemetic drug – domperidone administrated to beagle dogs has been carried out, the main pharmacokinetic parameters of levodopa with domperidone were as follows: Tmax (0.50 ± 0.18) h, Cmax (39.72 ± 7.91) μg/mL, tl/2 (0.65 ± 0.07) h, AUCo‐t (49.01 ± 12.13) μg·h/mL , AUCo‐∞ (49.10 ± 12.16) μg·h/mL, we also evaluated the effect of domperidone on pharmacokinetics of levodopa in beagle dog. We thought non‐oral sustained‐release formulations should be a very good choice instead of this common oral dosage forms on the market, the test results can provide a reference for clinical trials on drug therapy of Parkinson‘s disease.