Determination of L-365,260, a new cholecystokinin receptor (CCK-B) antagonist, in plasma by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry.

L-365,260 is a novel cholecystokinin receptor antagonist. A sensitive and specific liquid chromatographic/mass spectrometric assay has been developed for the determination of the drug in plasma using the CD3-labeled species as the internal standard. Plasma extracts were separated on a 3 cm C18 reverse-phase high-performance liquid chromatography column. The column eluate passed, by means of a heated nebulizer interface, into a corona discharge atmospheric chemical ionization source. The mass spectrometer was operated in the positive ion tandem mass spectrometric mode. The method has sufficient sensitivity, specificity, precision, accuracy and selectivity for the determination of drug concentrations in clinical samples. The chromatographic run time is less than 2 min.