Pharmacokinetic estimation of losartan, losartan carboxylic acid and hydrochlorothiazide in human plasma by LC/MS/MS validated method

A novel LC-ESI-MS, validated simultaneous method is described for losartan, its active metabolite - losartan carboxylic acid (LCA) and hydrochlorothiazide (HCTZ) using irbesartan, candesartan and hydroflumethiazide (HFMZ) as internal standards respectively. A simple solid-phase extraction technique, excellent chromatographic separation on a C18Discovery column (4.6 x 50 mm, 5μm) within 3 minutes, negative mode MRM transitions m/z 421.3/156.9, m/z 427.2/193.1, m/z 435.3/157.1, m/z 439.4/309.1, m/z 330.0/238.8, and m/z 439.0/309.2 for losartan, HCTZ, LCA, irbesartan, HFMZ, candesartan respectively with dynamic linearity range of 2.54 ng/mL to 1509.56 ng/mL for losartan, 3.27 ng/mL to 1946.38 ng/mL for LCA and 2.10 ng/mL to 410.40 ng/mL for HCTZ are unique results of this investigation. Pharmacokinetic parameters are evaluated from 60 fasting, healthy male volunteers administered with a fixed-dose oral tablet formulation of losartan potassium 100 mg and hydrochlorothiazide 25 mg tablet in a randomized, single dose, 4 way cross-over study involving 36 hrs post dose serial blood collection. Results by non compartmental pharmacokinetic analysis assessed for 90% CI (obtained by ANOVA) for Cmax-93.37%, 98.67%, 103.60%, AUC0-t -101.43%, 100.15%, 103.94% and AUC0-∞-101.73%, 98.76%,103.39% for losartan, LCA, and HCTZ respectively were well within the predefined range (80-125%) and therefore determined to be bioequivalent in terms of rate and extent of absorption. Copyright © Informa UK, Ltd.