Liquid chromatography–tandem mass spectrometry determination of bumetanide in human plasma and application to a clinical pharmacokinetic study

Abstract Determining a drug's bioavailability and bioequivalence is important for developing and approving a drug product. The procedure supports applications for generic drug products and novel therapeutic substances, makes important decisions regarding safety and efficacy, and measures a drug's concentration in biological matrices. This study aimed to develop and validate a specific, simple, sensitive, and accurate method using liquid chromatography–tandem mass spectrometry (LC–MS) for measuring bumetanide (BUM) in human plasma. Chromatographic separation was achieved using a Hypurity C18 column (4.6 × 50 mm, 5 μm) under isocratic conditions, and LC–MS detected positive ionization acquisition modes. Protonated precursor to product ion transitions were observed at m/z 365.08 → 240.10 and 370.04 → 244.52 for BUM and internal standard, respectively. The linear range of BUM in plasma samples was 3.490–401.192 ng/mL. The inter‐precision value ranged from 1.76% to 4.75%. The inter‐accuracy value ranged from 96.46% to 99.95%. The method was adequately validated per the U.S. Food and Drug Administration guidelines, and the results were within permissible bounds. The C max and T max values were ~53.097 ± 13.537 ng/mL and 1.25 (0.67–5.00) h, respectively. The new approach showed satisfactory results for studying BUM in human plasma with potential use in pharmacokinetic and bioequivalence investigations.