Abstract: Aim To evaluate the bioequivalence of two brands of losartan/hydrochlorothiazide (50 mg/12.5 mg) compound tablets in healthy Chinese male volunteers. Methods An open, randomized, single-dose, two-period cross-over studywith a wash-out period of 7 d was conducted. Twenty healthy male volunteers were givena single dose 50 mg losartan/12.5 mg hydrochlorothiazide of either test (T) or reference (R) compound tablets,respectively. Blood samples were collected up to 48 h after oral administration. The concentrations of losartan and hydrochlorothiazide in plasma were determined by a validated HPLC-ESI-MS method. Results In the case of losartan, the 90% confidence intervals of two one-side test for percent ratios with a significant level (α) of 0.05 were 86% – 112% for AUC_0-120 and 89% – 134% for C_max, respectively, which were within the interval proposed in the Chinese Pharmacopoeia, 80% – 125% of AUC and 70% – 143% of C_max, respectively. Similarly, the 90% confidence intervals for percent ratios were 85% – 100% and 75% – 102% for hydrochlorothiazide, both of which fell into the accepted interval. Conclusion Two immediate-release compound tablets of losartan/hydrochlorothiazideare bioequivalent from a statistical standpoint in the extent and rate of absorption from the single-dose study in healthy Chinese male volunteers.

Key words: losartan, losartan, hydrochlorothiazide, hydrochlorothiazide, bioequivalence, bioequivalence, HPLC-ESI-MS, HPLC-ESI-MS