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Quantitative determination of nitrendipine and its metabolite dehydronitrendipine in human plasma using liquid chromatography-tandem mass spectrometry.

A sensitive and high-throughput LC-MS-MS method was developed for simultaneous determination of nitrendipine (NIT) and its major metabolite, dehydronitrendipine (DNIT) in human plasma using nifedipine as the internal standard. Plasma samples were prepared based on a simple liquid-liquid extraction. The extracted samples were analyzed on a Zorbax SB C(18) column interfaced with a triple quadrupole tandem mass spectrometer. Positive atmospheric pressure chemical ionization was employed as the ionization source. The analytes were detected by use of selected reaction monitoring mode. Standard curves were linear (r > or = 0.995) over the concentration range of 0.4-40 ng/mL for NIT and 0.2-20 ng/mL for DNIT. The intra- and inter-run precision was measured to be below 8.5% for NIT and DNIT. The inter-run accuracy was less than 4% for the analytes. The overall extraction recoveries of NIT and DNIT were determined to be about 75% and 78% on average, respectively. The chromatographic run time was approximately 3 min. More than 120 samples could be assayed daily with this method, including sample preparation, data acquisition and processing. The method developed was successfully used to investigate plasma concentrations of NIT and DNIT in a pharmacokinetic study of volunteers who received NIT orally.