Effects of Paeoniflorin on the Pharmacokinetics of Glycyrrhizic Acid and Glycyrrhetinic Acid in Rats

[Objective] To explore the effects of paeoniflorin on the pharmacokinetics of glycyrrhizic acid and its active metabolite glycyrrhetinic acid after. [Method] After the administration of single glycyrrhizic acid or co-administration with paeoniflorin, blood samples were collected at different time points. The plasma concentration-time curves of glycyrrhizic acid and glycyrrhetinic acid were established. And pharmacokinetic parameters were calculated and analyzed by Topfit 2.0 software. [Result] Peak concentration (Cmax) and AUC of glycyrrhizic acid after co-administration with paeoniflorin reduced to 9% and 33% of those after administration of single glycyrrhizic acid, respectively. Tmax prolonged significantly; CL increased and Vd became larger. As for glycyrrhetinic acid, only the t1/2 prolonged significantly while other pharmacokinetic parameters had little changes. [Conclusion] Paeoniflorin dramatically inhibited the absorption rate and extent of glycyrrhizic acid in rats, but had only small effects on the absorption of glycyrrhetinic acid.