Development and validation of a LC-ESI-MS/MS method for simultaneous quantification of olmesartan and hydrochlothiazide in human K3 EDTA plasma and its application to pharmacokinetic biostudy

This is the first publication on a complete validated bioanalytical method for estimation of olmesartan (OLM) and hydrochlorothiazide (HCTZ) in human K3 EDTA plasma that chromatographically resolves its olmesartan glucuronide. An API 4000 mass spectrometer was employed in this method where olmesartan d4 (OLMD4) and hydrochlorothiazide ?¹³C, d2 (HCTZD2) served as the internal standard. Sample was prepared by solid phase extraction (SPE) technique using a polymer based, MCX cartridges and chromatographic resolution achieved on Synergi MAX RP-18A, (4.6?×?150?mm, 4?μm) column using a mobile phase of 0.2% formic acid solution/acetonitrile (30:70, v/v). Negative mass transitions (m/z) of OLM, HCTZ, OLMD4, and HCTZD2 were detected in multiple reactions monitoring (MRM) mode at 445.5?→?149.3, 296.0?→?269.0, 449.2?→?149.3, and 299.1→270.0, respectively. The linearity was checked over a concentration range of 4.051–2500.912?ng/mL for OLM and 0.506–304.109?ng/mL for HCTZ. Intra- and inter-run precision of OLM and HCTZ assay at four concentration levels were below 3.7% and 4.3%, and accuracy was within ±4.4% and 3.0%, respectively. Mean recoveries for OLM, HCTZ, and internal standards OLMD4 and HCTZD2 were 75.68, 77.60%, and 80.2, 89.1%, respectively. This method has been successfully applied to pharmacokinetic biostudy.