A liquid chromatography-tandem mass spectrometric assay for the antihypertensive agent azelnidipine in human plasma with application to clinical pharmacokinetics studies.

A robust and sensitive high-performance liquid chromatographic-tandem mass spectrometric (HPLC-MS/MS) assay for the high-throughput quantification of the antihypertensive drug azelnidipine in human plasma was developed and validated following bioanalytical validation guidelines. Azelnidipine and internal standard (IS), telmisartan, were extracted from human plasma by precipitation protein and separated on a C18 column using acetonitrile-methanol-ammonium formate with 0.1% formic acid as mobile phase. Detection was performed on a turbo-spray ionization source (ESI) and mass spectrometric positive multiple reaction monitoring mode (+MRM) using the respective transitions m/z 583.3 → 167.2 for azelnidipine and m/z 515.3 → 497.2 for IS. The method has a wide analytical measuring range from 0.0125 to 25 ng/mL. For the lowest limit of quantitation, low, medium and high quality controls, intra- and interassay precisions (relative standard deviation) were 3.30-7.01% and 1.78-8.09%, respectively. The drug was sufficiently stable under all relevant analytical conditions. The main metabolite of azelnidipine, M-1 (aromatized form), was monitored semiquantitatively using the typical transition m/z 581.3 → 167.2. Finally, the method was successfully applied to a clinical pharmacokinetic study in human after a single oral administration of azelnidipine 8 mg. The assay meets criteria for the analysis of samples from large research trials.