Human Bioequivalence Evaluation of Two Losartan Potassium Tablets Under Fasting Conditions

The bioequivalence of two different tablet formulations containing losartan potassium 100 mg was determined in healthy volunteers after a single oral dose in a randomized crossover study. Test and reference products were administered to 60 volunteers with 240 ml water after overnight fasting. Plasma concentrations of losartan and its active carboxylic acid metabolite were monitored over a period of 36 h after drug administration by validated LC/MS/MS analytical method. The pharmacokinetic parameters C(max), AUC(0-t), AUC(0-∞), AUC(0-t)/AUC(0-∞), t(max), K(el) and t(½) were determined from plasma concentration time profile of both formulations for losartan and its active metabolite losartan carboxylic acid and were found to be in good agreement. The carboxylic acid metabolite was considered for profiling purpose only. The analysis of variance did not show any significant difference between the two formulations and 90% confidence intervals for the ratio of C(max) (84.89-104.09%), AUC(0-t) (95.84-102.84%) and AUC(0-∞) (96.43-103.25%) values for losartan between the test and reference products were within the 80-125% interval, satisfying the bioequivalence criteria of the US FDA guidelines. These results indicate that the test and the reference products of losartan potassium are bioequivalent and, thus, may be prescribed interchangeably.