The pharmacokinetics of Tiangou antihypertensive capsule in rat in vivo

The aim of the study was to examine the effect of complex prescription on the pharmacokinetics of baicalin, rhynochophylline and gastrodin in Tiangou antihypertensive capsule. After administration, rat plasma was collected at different time-points. High-performance liquid chromatography was used to determine the content of baicalin, rhynochophylline and gastrodin in plasma. Two peaks occurred in the baicalin concentration-time curve. No significant difference was found for the peak concentration time (t_max) and area under concentration-time curve (AUC) of baicalin between the complex prescription and baicalin groups. The peak concentration (C_max) of baicalin in the complex prescription group was significantly decreased, while no significant difference was found for the absorption factor (K_a) and AUC of baicalin between the complex prescription and gastrodin groups. The elimination factor (K_e) of gastrodin in the complex prescription group was significantly decreased, while the apparent volume of distribution (Vd) of gastrodin was significantly increased. No significant difference was found for AUC of baicalin between the complex prescription and rhynochophylline groups. Levels of K_a and K_e of rhynochophylline were lower in the complex prescription group while Vd was higher. Thus, complex prescription made plasma concentration-time curve more smooth. By contrast, the Tiangou antihypertensive capsule improved the distribution of baicalin, rhynochophylline and gastrodin in vivo.