Simultaneous analysis of losartan, its active metabolite, and hydrochlorothiazide in human plasma by a UPLC-MS/MS method

Quantitation was performed with multiple reaction monitoring in the negative ionization mode. The response of the method was linear over a dynamic range of 0.5–500, 1.0–750, and 0.25–150 ng/mL for LOS, EXP-3174, and HCTZ, respectively. Extent of signal suppression/enhancement was examined through postcolumn infusion. The effect of matrix components was evaluated by postextraction spiking and calculation of the slope of calibration lines. The method was successfully applied to a bioequivalence study of 50 mg losartan and 12.5 mg hydrochlorothiazide tablet formulation in 65 healthy human subjects. Reproducibility of the method was shown by reanalysis of 213 incurred samples.