Determination of parthenolide in rat plasma by UPLC-MS/MS and its application to a pharmacokinetic study.

A rapid, sensitive and selective ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the determination and pharmacokinetic investigation of parthenolide in rat plasma. Sample preparation was accomplished through a simple one-step deproteinization procedure with 0.2mL of acetonitrile containing 30ng/mL of pirfenidone (IS), and to a 0.1mL plasma sample. Plasma samples were separated by UPLC on an Acquity UPLC BEH C18 column using a mobile phase consisting of acetonitrile-0.1% formic acid in water with gradient elution. The total run time was 3.0min and the elution of parthenolide was at 1.33min. The detection was performed on a triple quadrupole tandem mass spectrometer in the multiple reaction-monitoring (MRM) mode using the respective transitions m/z 249.2→231.1 for parthenolide and m/z 186.2→92.1 for pirfenidone (IS), respectively. The calibration curve was linear over the range of 2.0-500ng/mL with a lower limit of quantitation (LLOQ) of 2.0ng/mL. Mean recovery of parthenolide in plasma was in the range of 78.2-86.6%. Intra-day and inter-day precision were both <8.3%. This method was successfully applied in pharmacokinetic study after oral and intravenous administration of parthenolide in rats.

Effects of Evodiamine on the Pharmacokinetics of Dapoxetine and Its Metabolite Desmethyl Dapoxetine in Rats.

The objective of this work was to investigate the effect of orally administered evodiamine on the pharmacokinetics of dapoxetine and its active metabolite desmethyl dapoxetine in rats. Twelve healthy male Sprague-Dawley rats were randomly divided into 2 groups: the control group (received oral 10 mg/kg dapoxetine alone) and the combination group (10 mg/kg dapoxetine orally co-administered with 100 mg/kg evodiamine). The plasma concentration of dapoxetine and desmethyl dapoxetine were estimated by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and different pharmacokinetic parameters were calculated using the Drug and Statistics 2.0 software. Compared to the control group, the pharmacokinetic parameter of t1/2, AUC(0-∞) and Tmax of dapoxetine in combination group was significantly increased by 63.3% (p < 0.01), 44.8% (p < 0.01) and 50.4% (p < 0.01), respectively. Moreover, evodiamine had significantly decreased the pharmacokinetic parameter of t1/2 and AUC(0-∞) of desmethyl dapoxetine. This study demonstrated that evodiamine inhibits the metabolism of dapoxetine. Henceforth, the pharmacodynamic influence of this interaction should be taken into consideration while prescribing dapoxetine to the patients already taking evodiamine.