Simultaneous determination of multiple angiotensin type 1 receptor antagonists and its application to high-throughput pharmacokinetic study: Cassette dosing versus cassette analysis

A rapid and sensitive high performance liquid chromatography-electrospray tandem mass spectrometry (HPLC-ESI–MS/MS) detection was developed for the simultaneous determination of multiple angiotensin type 1 receptor antagonists (AT1RAs) WX472, WX581, 1b and telmisartan in rat plasma for the purpose of high-throughout pharmacokinetic screening. The method was operated under selected reaction monitoring (SRM) mode in the positive ion mode. The analytes and the internal standard (pitavastatin) were extracted from 100 μL rat plasma under acidic conditions by liquid–liquid extraction with ethyl acetate. The analytes and internal standard were baseline separated on a Gemini analytical column (3 μm, 150 mm × 2.0 mm) with the adoption of a gradient elution using acetonitrile and 0.05% aqueous formic acid. The standard curves were linear in the concentration ranges of 4.5–900 ng/mL for WX472, 5–1000 ng/mL for WX581 and 0.5–100 ng/mL for 1b and telmisartan. Intra- and inter-batch precisions (R.S.D.%) were all within 15% and the method assessed a quite good accuracy (R.E.%). Recoveries were found to be >65% for all the compounds and no obvious matrix effects were found. This method has been successfully applied to the high-throughput pharmacokinetic screening study for both cassette dosing and cassette analysis of four compounds to rats. Significant drug–drug interactions were observed after cassette dosing. The study suggested that cassette analysis of pooled samples would be a better choice for the high-throughput pharmacokinetic screening of angiotensin type 1 receptor antagonists.