A liquid chromatography-tandem mass spectrometry method for the determination of idazoxan in human (heparin) plasma is presented, which was developed and validated using 500 microl of sample. Sample preparation consisted of the addition of fluoroidazoxan as the internal standard, extraction at alkaline conditions into tert.-butyl methyl ether, followed by centrifugation, evaporation of the solvent and reconstitution in methanol. After a short chromatographic run, detection took place by ionspray tandem mass spectrometry in positive ion mode. Validation results on linearity, specificity, accuracy, precision and stability, as well as application of the method to samples from a clinical trial, are shown. The validated calibration range is from 0.300 to 100 ng/ml, with accuracy (bias) and precision (coefficient of variation) being below 15% at all levels. A sample throughput of, typically, 150 per day can be achieved.
