| AIM:To determine rabeprazole in human plasma after intravenous injection at three dosage levels of rabeprazole sodium injection, a rapid, selective and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed, and the method was successfully applied to study the clinical pharmacokinetic of rabeprazole in healthy volunteers.STUDY METHOD: Rabeprazole and internal standard (I.S.), omeprazole, were extracted from plasma (50μL) by liquid-liquid extraction with acetic ether?and then separated on a Extend-C18 column (4.6×150 mm I.D.,5μm) using methanol - 0.4% ammonia water (50:50, v/v) as mobile phase at a flow rate of 1.0 mL·min-1. An approximately 1:1 split of the column eluate was included allowing 0.5 mL·min-1 to enter the mass spectrometer. Mass spectrometric detection utilized an API 4000 mass spectrometer equipped with an ESI (electrospray ionization) source operated in the positive ion mode. MRM (multiple reaction monitoring) transitions were m/z 360.3→m/z 242.1 for rabeprazole and m/z 346.2→m/z 198.2 for omeprazole. The full validation was carried out to test the precision, accuracy, recoveries, matrix effects and stability.12 healthy volunteers were given intravenous injection at three dosage levels of rabeprazole sodium injection (10 mg, 20 mg, and 40 mg respectively). The rabeprazole concentration in human plasma was determined by the validated LC-MS/MS method. The main pharmacokinetic parameters were calculated and analyzed to evaluate the correlation.RESULTS:The assay developed and validated a selective, rapid, robust, and sensitive LC-MS/MS method with the LLOQ 1 ng/mL, and determined rabeprazole in human plasma after intravenous injection at three dosage levels of rabeprazole sodium injection (10 mg, 20 mg and 40 mg respectively). The linearity of the method was 1 3000 ng/mL. Intra- and inter-day precision (as relative standard deviation, R.S.D.) were≤6.12% and≤7.20%, respectively, and accuracy (as relative error, R.E.) was from -4.57% to 0.26%. The assay was free of interference from endogenous substances in plasma. The sample preparation procedure can efficiently extract the analyte and I.S. with minimal matrix effects. In the assay rabeprazole proved to be stable under all the conditions tested. Assay validation was performed according to SFDA guidelines and indicated the method is suitable for the pharmacokinetic study of rabeprazole sodium injection in human plasma. Because of the high sensitivity and selectivity, short run time and simple sample preparation, the method allows high sample throughput for clinical studies.After intravenous injection at three dosage levels of rabeprazole sodium injection (10 mg, 20 mg, and 40 mg respectively), the pharmacokinetic parameters of 12 healthy volunteers are as follows: Cmax: 451.58±78.85 ng·mL-1, 880.42±207.42 ng·mL-1 and 1802.25±431.04 ng·mL-1 respectively; AUC0-t: 624.11±126.39 ng h·mL-1, 1173.62±243.20 ng h·mL-1 and 2479.58±735.17 ng h·mL-1 respectively; AUC0-∞: 629.85±133.74 ng h·mL-1, 1180.72±250.82 ng h·mL-1 and 2498.87±767.43 ng h·mL-1 respectively; t1/2: 1.52±0.56 h, 1.56±0.30 h and 1.57±0.34 h respectively; CL: 273±45.45 mL/min, 293±55.20 mL/min and 287±77.92 mL/min respectively; Vd: 31.8±9.52 L, 38.48±12.12 L and 38.54±12.07 L respectively; MRT: 1.42±0.46 h, 1.42±0.32 h and 1.47±0.37 h respectively.The main pharmacokinetic parameters (Cmax, AUC0-t and AUC0-∞) were linearly increased with the increasing of doses in the dose of 10 40 mg which indicated the linear pharmacokinetic characteristics. But the other pharmacokinetic parameters such as t1/2, CL, Vd and MRT were not varied with the increasing of doses.
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