Chromatography-tandem mass spectrometry method for the simultaneous quantitation of metoprolol succinate and simvastatin in human plasma

The liquid chromatographic-tandem mass spectrometry method was developed for the accurate quantitation of metoprolol succinate (MET) and simvastatin (SIM) in human plasma which were obtained from the pharmacokinetic (PK) study. The sample purification and pre-concentration was performed by protein precipitation technique using propranolol hydrochloride as working internal standard (WIS). The chromatographic separation was achieved using an isocratic mobile phase consisting of a mixture of acetonitrile and 0.5% formic acid (90:10 (v/v), pH 3.5) flowing through C18 column at a flow rate of 0.2 ml/min. Electro spray ionization (ESI) with multiple reaction monitoring (MRM) was used to acquire mass spectra. Ions were monitored in positive mode and the mass transitions measured were m/z 268.1 → m/z 103.2, m/z 441.3 → m/z 325.1 and m/z 260.0 → m/z 129.5 for MET, SIM and WIS, respectively. An extensive pre-study method validation was carried out in accordance with USFDA guidelines. The linearity for the calibration curve in the concentration range of 1.0-500.0 and 0.1-20 ng/ml for MET and SIM, respectively and the lower limits of quantitations (LLOQ) were 1.0 and 0.1 ng/ml for MET and SIM, respectively. The method was successfully applied to a PK study on fixed dose combination (FDC) tablet containing MET and SIM in healthy human subjects.