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.