Determination of olopatadine, a new antiallergic agent, and its metabolites in human plasma by high-performance liquid chromatography with electrospray ionization tandem mass spectrometry.

A rapid, sensitive and specific assay method has been developed to determine plasma concentrations of olopatadine hydrochloride (A) and its metabolites, M1 (B), M2 (C) and M3 (D), using high-performance liquid chromatography with electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS). Olopatadine, its metabolites, and internal standard, KF11796 (E), were separated from plasma using solid-phase extraction (Bond Elut C18 cartridge). The eluate was dried, reconstituted and injected into the LC-ESI-MS-MS system. The calibration curves showed good linearity over the ranges 1-200 ng/ml for olopatadine and M3, and 2-100 ng/ml for M1 and M2, and the method was thoroughly validated and applied to the determination of olopatadine and its metabolites in plasma collected during Phase I clinical trials. Furthermore, the assay values were compared with those determined by the radioimmunoassay method, which has been routinely used to determine olopatadine in plasma.