Determination And Pharmacokinetics Studies Of Amlodipine And Nimodipine In Human Plasma By Ultra Performance Liquid Chromatography-tandem Mass Spectrometry

Objective: To develop and validate rapid, sensitive and specific methods for the determination and pharmacokinetics studies of amlodipine and nimodipine in human plasma by ultra performance liquid chromatography-tandem mass spectrometry.Method: After a liquid-liquid extraction process with ether, amlodipine and nimodipine (internal standard) were separated on an ACQUITY UPLC^TM BEH C₁₈ column (50mm×2.1mm, i. d., 1. 7μm) with gradient elution at a flow-rate of 0.35 ml/min. The mobile phase was a mixture of water and acetonitrile (both containing 0.3 % formic acid). The detection was performed on a triple-quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode via Turbo ion spray ionization (ESI). The quantification was performed using the transitions of m/z 409→238 for amlodipine and m/z 419→343 for nimodipine (internal standard), respectively.Nimodipine plasma samples were prepared by liquid-liquid extraction, separated on ACQUITY UPLC^TM BEH C₁₈ column with gradient elution and a switch technology. The mobile phase was water and acetonitrile (both containing 0.1% formic acid). Multiple reaction monitoring (MRM) using the precursor→product ion combination of m/z 419→343, and m/z 361→315 was used to quantify nimodipine and nitrendipine (internal standard), respectively.Result: The linear calibration curves were obtained over the concentration range 0.15～16.0 ng/ml for amlodipine. The intra- and inter-day precision values (RSD) were not above 9.0% and the accuracy (RE) was -2.3%～6.9% at all three QC levels. The standard calibration curves for nimodipine were linear in the concentration range of 0.20～100 ng/ml in human plasma. The intra- and inter-day precision values (RSD) were not above 13.9 % and the accuracy (RE) was2.2%～7.7% at all three QC levels.Conclusion: The method was applicated to study the pharmacokinetics of 20 healthy volunteers after oral administration of 10 mg of amlodipine. Mean peak plasma levels (C_max) of 9.5±2.7 ng/mL and T_max of 5.2±1.5 h were observed. The mean t_1/2 value of 32.0±6.7 h was obtained, AUC_0-t and AUC_0-∞ were calculated to be 330.2±106.0 ng'h/mL and 385.7±139.0 ng'h/mL, respectively. The main parameters obtained after an oral dose of 60 mg nimodipine to 11 healthy volunteers were as follows: Cmax were found to be 12.7±9.0 ng/mL, T_max observed was 1.6±0.6 h, the value t_1/2 was 2.5±0.5 h, AUC_0-t and AUC_0-∞ obtained were 50.5±19.8 ng.h/mL and 53.7±20.2 ng'h/mL, respectively. The methods are proved to be of high specificity, speed, sensitivity and have been successfully utilized for the evaluation of the pharmacokinetics of amlodipine and nimodipine.