Simultaneous quantitation of metformin and dapagliflozin in human plasma by LC-MS/MS: Application to a pharmacokinetic study

A single LC-MS/MS assay has been developed and validated for the simultaneous determination of metformin and dapagliflozin in human plasma using ion-pair solid-phase extraction. Chromatographic separation of the analytes and their internal standards was carried out on a reversed-phase ACE 5CN (150 x 4.6 mm, 5 mu m) column using acetonitrile-15 mm ammonium acetate, pH 4.5 (70:30, v/v) as the mobile phase. To achieve higher sensitivity and selectivity for the analytes, mass spectrometric analysis was performed using a polarity switching approach. Ion transitions studied using multiple reaction monitoring mode were m/z 130.1 [M + H](+)/60.1 for metformin and m/z 467.1 [M + CH3COO](-)/329.1 for dapagliflozin in the positive and negative modes, respectively. The linear calibration range of the assay was established from 1.00 to 2000 ng/mL for metformin and from 0.10 to 200 ng/mL for dapagliflozin to achieve a better assessment of the pharmacokinetics of the drugs. The limit of detection and limit of quantitation for the analytes were 0.39 and 1.0 ng/mL for metformin and 0.03 and 0.1 ng/mL for dapagliflozin, respectively. There was no interference of plasma matrix obtained from different sources, including hemolyzed and lipemic plasma. The method was successfully applied to study the effect of food on the pharmacokinetics of metformin and dapagliflozin in healthy subjects.