Development and full validation of a quantitative assay for the determination of valsartan in human plasma and its application for bioequivalence study

A selective, suitable and reproducible HPLC-UV method was developed and validated for the determination and pharmacokinetic investigation of valsartan in human plasma. Valsartan and internal standard (IS), irbesartan, were extracted from plasma samples using liquid–liquid extraction with ethyl acetate + n-hexane (80:20). Chromatographic separation was performed on a Lichrosphere C18 RP Select B column (250 × 4.0 mm i.d; 5 µm particle size) using 20-mM potassium dihydrogen orthophosphate buffer (pH adjusted to 2.7 ± 0.05 using 50% orthophosphoric acid):acetonitrile (60:40 v/v) as the mobile phase at flow rate of 1.2 ml/min. The effluent was monitored using ultraviolet (UV) detection set at 225 nm, having column oven temperature 40°C and sample cooler temperature 8°C ± 0.2°C. The calibration curve was linear over the range of 217.7–6118.4 ng/mL. The intra- and inter-day precisions were within 8.6% and 7.4%, respectively, whereas accuracies were 101.0–107.9% and 103.4–109.5%, respectively. The validated method was successfully applied for the evaluation of pharmacokinetic and bioequivalence parameters of valsartan after oral administration of 160 mg tablets in 18 healthy volunteers.