Sensitive quantification of ranolazine in human plasma by liquid chromatography–tandem mass spectrometry with positive electrospray ionization

A rapid, selective and sensitive liquid chromatography–tandem mass spectrometry (LC–MS–MS) method with positive electrospray ionization (ESI) was developed for the quantification of ranolazine in human plasma. After liquid–liquid extraction of ranolazine and internal standard (ISTD) phenoprolamine from a 100 μl specimen of plasma, HPLC separation was achieved on a Nova-Pak C18 column, using acetonitrile–water–formic acid–10% n-butylamine (70:30:0.5:0.08, v/v/v/v) as the mobile phase. The mass spectrometer was operated in multiple reaction monitoring (MRM) mode using the transition m/z 428.5 → m/z 279.1 for ranolazine and m/z 344.3 → m/z 165.1 for the internal standard, respectively. Linear calibration curves were obtained in the concentration range of 5–4000 ng/ml, with a lower limit of quantitation (LLOQ) of 5 ng/ml. The intra- and inter-day precision values were below 3.7% and accuracy was within ±3.2% at all three quality control (QC) levels. This method was found suitable for the analysis of plasma samples collected during the phase I pharmacokinetic studies of ranolazine performed in 28 healthy volunteers after single oral doses from 200 mg to 800 mg.