Quantification of furosemide in camel plasma by high resolution mass spectrometry, application on pharmacokinetics

We developed and validated a high-resolution liquid chromatography mass spectrometry method for the quantification of furosemide in camel plasma which was used for a pharmacokinetic study in camels. Plasma samples were extracted by supported liquid extraction and furosemide and internal standard (furosemide-D5) were separated on a an Agilent Zorbax XDB C₁₈ column (50 × 2.1 mm i.d., 3.5 μm). Data was acquired in full-scan mode over a mass range of 200-400 Da in negative electrospray mode at a resolution of 70,000. Linear calibration curves were obtained over the concentration ranges of 1.0-10,000 ng/mL. The validated method was then successfully applied in evaluating the pharmacokinetics and metabolites of furosemide in six camels (Camelus dromedarus) and we were able to advice on a withdrawal time of furosemide treatment before racing.