Liquid chromatography-tandem mass spectrometry method for the determination of meloxicam and its metabolite 5-carboxymeloxicam in human plasma.

To develop and validate a rapid, sensitive and selective liquid chromatography-electrospray ionization mass spectrometric method for the determination of meloxicam and its metabolite 5-carboxymeloxicam in human plasma. A liquid extraction method was chosen for sample clean-up. Meloxicam, 5-carboxymeloxicam and isoxicam (internal standard) were analyzed on an XBridge™ C18 column with 65% methanol in 10 mM ammonium formate (pH 3.0) and detected in selected reaction monitoring mode. The standard curves were linear over the concentration range 10-2500 ng/ml for meloxicam and 2-100 ng/ml for 5-carboxymeloxicam. Matrix effects were practically absent. This method has been successfully applied to the pharmacokinetic study of meloxicam and 5-carboxymeloxicam after oral administration of meloxicam (15 mg) to 30 volunteers.