Liquid chromatographic-mass spectrometric determination of celecoxib in plasma using single-ion monitoring and its use in clinical pharmacokinetics.

Celecoxib is a cyclooxygenase-2 specific inhibitor, that has been recently and intensively prescribed as an anti-inflammatory drug in rheumatic osteoarthritis. A robust, highly reliable and reproducible liquid chromatographic-mass spectrometric assay is developed for the determination of celecoxib in human plasma using sulindac as an internal standard. The run cycle-time is <4 min. The assay method involved extraction of the analytes from plasma samples at pH 5 with ethyl acetate and evaporation of the organic layer. The reconstituted solution of the residue was injected onto a Shim Pack GLC-CN, C18 column and chromatographed with a mobile phase comprised of acetonitrile-1% acetic acid solution (4:1) at a flow-rate of 1 ml/min. The mass spectrometer (LCQ Finnigan Mat) was programmed in the positive single-ion monitoring mode to permit the detection and quantitation of the molecular ions of celecoxib and sulindac at m/z 382 and 357, respectively. The peak area ratio of celecoxib/sulindac and concentration are linear (r2>0.994) over the concentration range 50-1000 ng/ml with a lowest detection limit of 20 ng/ml of celecoxib. Within- and between-day precision are within 1.58-4.0% relative standard deviation and the accuracy is 99.4-107.3% deviation of the nominal concentrations. The relative recoveries of celecoxib from human plasma ranged from 102.4 to 103.3% indicating the suitability of the method for the extraction of celecoxib and I.S. from plasma samples. The validated LC-MS method has been utilized to establish various pharmacokinetic parameters of celecoxib following a single oral dose administration of celecoxib capsules in two selected volunteers.