HPLC-MS-MS determination of ritodrine in the human plasma and its pharmacokinetics

AIM: To establish an HPLC-MS-MS method for determination of ritodrine in human plasma and to study the pharmacokinetics for two preparations in health volunteers.METHODS: The plasma was extracted with ethyl acetate.Separation was obtained on BDS Hypersil C18(3 μm,2.1 mm×50 mm)column with the mobile phase of water(1‰ formic acid)-methanol(20∶80) at the flow rate of 0.20 mL/min.Electrospray ionization source was operated in positive ion mode.Selected reaction monitoring mode with the transitions of m/z 288/270 and m/z 373.4/305.3 were used to quantify ritodrine and the internal standard,respectively.RESULTS:The calibration curve of ritodrine was linear in the range of 0.13-8 ng/mL and detection limit was 0.13 g/L.The intra and inter-day precision(RSD) were less than 12.5%.The absolute recoveries were above 75.4%.To study the pharmacokinetics and the relative bioavailability of two preparations of ritodrine,tablets were given to 18 healthy volunteers.The pharmacokinetics parameters were reported: Cmax were(6.1±1.9) and(5.8±2.1) ng/mL;tmax were(1.1±0.4) h and(1.2±0.4) h;t1/2 were(10±4) h and(9±5) h;AUC0-36 were(22±9) ng·mL-1·h and(21±8) ng·mL-1·h;AUC0-∞ were(25±10) ng·mL-1·h and(23±8) ng·mL-1·h.CONCLUSION: This method is convenient,sensitive,specific and suitable for pharmacokinetics and relative bioavailability study.