Effects of diammonium glycyrrhizinate on the pharmacokinetics of aconitine in rats and the potential mechanism

1. The objective of this study was to investigate the effects of diammonium glycyrrhizinate on the pharmacokinetics of aconitine in rats and the potential mechanism. 2. After oral administration of diammonium glycyrrhizinate (50mg kg^-1), the peak plasma concentration (C_max), area under the plasma concentrationtime curve from zero to time τ (AUC _0τ), and absolute bioavailability of aconitine (0.2mg kg ^-1) significantly increased 1.64-, 1.63-and 1.85-fold, respectively, but there was no significant change in half life (t_1/2) or clearance (CL). In the other two routes of administration via the tail vein and hepatic portal vein, diammonium glycyrrhizinate (15mg kg^-1) did not affect any of the pharmacokinetic parameters of aconitine (0.02mg kg^-1). Thus, diammonium glycyrrhizinate can enhance the absorption of aconitine, leading to higher oral bioavailability and plasma levels, but it does not influence its elimination. 3. Moreover, an in vitro everted gut sac model and Ussing chamber model were used to investigate the potential mechanism. Results from bidirectional transport and inhibition studies demonstrated that P-glycoprotein was the main efflux transporter involved in the absorption of aconitine in rats. The absorption enhancement effect of diammonium glycyrrhizinate should be mainly attributed to inhibiting the activity of P-glycoprotein rather than to the influence on the paracellular or transcellular transport.