Extractionless and sensitive method for high-throughput quantitation of cetirizine in human plasma samples by liquid chromatography–tandem mass spectrometry

Following a single 10-mg oral dose of cetirizine dihydrochloride to 24 healthy volunteers, the analyte was quantified in human plasma. Protein precipitation using acetonitrile (ACN) was followed by reversed-phase liquid chromatography and tandem mass spectrometry. The MS/MS method was optimised using a PE Sciex API 2000 triple quadrupole mass spectrometer in selected reaction monitoring (SRM) mode, using electrospray with positive ionisation. Oxybutynin was used as the internal standard. The assay method represents a robust, high-throughput, highly specific and sensitive quantitative assay procedure, with 0.5 ng/ml being the lowest plasma concentration that could be reliably quantified. The procedure involves minimal sample preparation, and is well suited to clinical studies of the drug involving large numbers of generated samples. Pre-dose as well as post-dose samples up to and including 48 h were quantified, and the data generated were used to determine the pharmacokinetic profile of the drug.