Simultaneous determination of the histamine H-1-receptor antagonist ebastine and its two metabolites, carebastine and hydroxyebastine, in human plasma using high-performance liquid chromatography

Ebastine (CAS 90729-43-4) is an antiallergic agent which selectively and po tently blocks histamine H-1-receptors in vivo. A simple and sensitive high- performance liquid chromatography (HPLC) method is described for the simult aneous determination of ebastine and its two oxidized metabolites, carebast ine (CAS 90729-42-3) and hydroxyebastine (M-OH), in human plasma. After a p retreatment of plasma sample by solid-phase extraction, ebastine and its me tabolites were analyzed on an HPLC system with ultraviolet detection at 254 nm. Chromatography was performed on a cyano column (250x4.0 mm I.D.) at 40 degreesC with the mobile phase of acetonitrile-methanol-0.012 M ammonium a cetate buffer (20.30:48, v/v/v) at a flow rate of 1.2 ml/min. Accurate dete rminations were possible over the concentration range of 3-1000 ng/ml for t he three compounds using 1 ml plasma samples. The intra, and inter-day assa y accuracy of this method were within 100+/-15% of nominal values and the p recision did not exceed 12.4% of relative standard deviation. The lower lim its of quantitation were 3 ng/ml for ebastine and its metabolites in human plasma. This method was satisfactorily applied to the determination of ebas tine and its two oxidized metabolites in human plasma after oral administra tion of ebastine. (C) 2001 Elsevier Science B.V. All rights reserved.