ABSORPTION AND EXCRETION OF PAEONIFLORIN IN RATS

The absorption and excretion of paeoniflorin after intravenous and ora l administration was studied in rats to evaluate the significance of p aeoniflorin in the pharmacological action of Paeony root. The plasma c oncentration of paeoniflorin after intravenous administration at the d oses of 0.5, 2.0 and 5.0 mg kg(-1) rapidly decreased, simulated by a b iexponential curve, with mean terminal half-lives of 11.0, 9.9 and 12. 6 min, respectively. The Vd(ss) values were 0.332, 0.384 and 0.423 L k g(-1) and the CL(tot) values were 26.1, 31.2 and 30.3 mL min(-1) kg(-1 ) at each dose. When given orally at the same doses, the absolute bioa vailability values (F) determined by the AUC were 0.032, 0.033 and 0.0 38, respectively. The cumulative urinary and faecal excretions of paeo niflorin at the dose of 5 mg kg(-1) after intravenous administration w ere 50.5 and 0.22% of the dose within 72 h, and 1.0 and 0.08% of the d ose after oral administration within 48 h, respectively. Cumulative bi liary excretion after intravenous or oral administration at a dose of 0.5 mg kg(-1) was 6.9 and 1.3% of the dose within 24 h, respectively. The total CL(R) and CL(B) value after intravenous dosing was less than the CL(tot) value. These findings suggest that paeoniflorin is metabo lized in other organs as well as in the liver. We conclude that paeoni florin absorbed is excreted mainly in urine, it has a low bioavailabil ity and the metabolites may be involved in the pharmacological action of Paeony root.