Determination of Tetrandrine in Rat Whole Blood by RP-LC and Its Application to Pharmacokinetic Studies

Abstract

A simple, specific and sensitive RP-LC method was developed and validated for the determination of tetrandrine in rat whole blood for the first time. Chromatographic separation was performed on a Welchrom^TM C18 analytical column at a flow rate of 1.0 mL min⁻¹, using a mixture of methanol-water containing 0.6% triethylamine and 0.16% phosphoric acid as mobile phase. The wavelength for UV detection was set at 225 nm. Sample preparation involved a liquid-liquid extraction using n-hexane. The calibration curve was linear with r ² > 0.99 over a concentration range of 0.03–6.4 μg mL⁻¹ in rat whole blood with a lower limit of quantification of 0.03 μg mL⁻¹. The intra- and inter-day precisions were 1.33–4.55 and 3.33–4.65%, respectively, and the intra- and inter-day accuracy ranged from −5.24 to 0.90% and −1.05 to 0.63%, respectively. No endogenous compounds were found to interfere with the analytes. Tetrandrine was stable for 8 h at room temperature, 24 h at 4 °C in rat whole blood, and for 30 days at −20 °C after being prepared. For the first time, the present method was successfully applied to the pharmacokinetic studies of tetrandrine in rats after intravenous administration of three different doses. The results indicated that the pharmacokinetics of tetrandrine on rats was a first-order process.