Determination of tezosentan, a parenteral endothelin receptor antagonist, in human plasma by liquid chromatography–tandem mass spectrometry

An analytical method was developed for the quantification of tezosentan in human plasma obtained in clinical studies. The method was linear in the range 1 to 512 ng/ml. After liquid–liquid extraction, the samples were analyzed by reversed-phase HPLC with tandem mass spectrometry. The limit of quantification was 1 ng/ml and the extraction recovery was at least 88.2%. Intra- and inter-assay coefficients of variation were below 10%. Stability tests revealed that tezosentan is stable under the different conditions tested.