Simultaneous determination of metoprolol succinate and amlodipine besylate in human plasma by liquid chromatography–tandem mass spectrometry method and its application in bioequivalence study

A simple, sensitive and specific liquid chromatography–tandem mass spectrometry method was developed and validated for quantification of metoprolol succinate (MPS) and amlodipine besylate (AM) using hydrochlorothiazide (HCTZ) as IS in human plasma. Both the drugs were extracted by simple liquid–liquid extraction with chloroform. The chromatographic separation was performed on a reversed-phase peerless basic C18 column with a mobile phase of methanol–water containing 0.5% formic acid (8:2, v/v). The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The method was validated over the concentration range of 1–100 ng/ml for MPS and 1–15 ng/ml AM in human plasma. The MRM transition of m/ z 268.10–103.10, m/ z 409.10–334.20 and m/ z 296.00–205.10 were used to measure MPS, AM and HCTZ (IS), respectively. This method was successfully applied to the pharmacokinetic study of fixed dose combination (FDC) of MPS and AM formulation product after an oral administration to Indian healthy human volunteers.