A simple, sensitive and rapid LC-MS/MS method has been developed and validated for the identification and quantification of bivalirudin in human plasma using nafarelin as the internal standard. Following protein precipitation with methanol, the analytes were separated on a C(18) column interfaced with a triple-quadrupole tandem mass spectrometer using positive electrospray ionization. Quantification of bivalirudin was conducted by multiple reaction monitoring (MRM) of the transitions of m/z 1091.4-->(356.4+227.4) for bivalirudin and m/z 662.4-->328.5 for IS. The lower limit of quantification was 1.25ng/ml, and the assay exhibited a linear range of 1.25-500ng/ml. The developed assay method was successfully applied to a pharmacokinetic (PK) study in healthy volunteers after intravenous administration of bivalirudin.
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