To investigate pharmacokinetics ofbaicalin after an oral administration of different Shuang-Huang-Lian （SHL） formulations to rats. Different SIlL formulations were orally administered to rats. The concentrations of baicalin in rat plasma were determined by HPLC, the non-compartmental pharmacokinetic parameters and population pharmacokinetic parameters of baicalin were estimated by WinNonlin and NONMEM. The plasma concentration profiles of baicalin demonstrated double-peak phenomenon except for group microemulsion prescription 2. Population pharmacokinetic model developed includes four covariates, which were the effect of formulation （FORM） on CL/F and V/F, the effect of body weight （BW） on Ka, and the effect of gender （GEND） on V/F. Numbers 1 to 6 denote SHL formulation decoction, oral liquid, colloidal solution, microemulsion prescription 1, microemulsion prescription 2 and granule, respectively. The equations for the parameters are as following： CL/F = （0.432 ＋ 0.529）. e^ηCl L/h if formulation was 2 or 6, otherwise CL/F = 0.432. e^ηCl L/h ; V/F = （11.3- 4.03 - 3.87. GEND）. e^ηv L if formulation was 5, otherwise V/F = （11.3 - 3.87. GEND）. e^ηv L ; Ka = 0.475. [1 - 0.0223. （BW - 195.1）]. e^ηKah^-1. SHL formulations have significant effects on the nharmacokinefic narameters.
To evaluate the effect of components in Guanxin Ⅱ prescription on the pharmacokinetic profiles of paeoniflorin. Plasma concentration of Paeoniflorin in rats after intravenous injection of Paronia Pall Extract （PPE） and oral administration of PPE and three types of decoctions in Guanxin Ⅱ prescription, respectively, were determined by HPLC analyses. NONMEM （nonlinear mixed-effect modeling） method was used to analyze full set of pharmacokinetic data directly. A two-compartment model with first-order degradation in absorption compartment was employed for the data analysis. The mean of population parameters, CL1, V1, CL2, V2, Ka0, and Kal, were measured to be 0.509 L/h, 0.104 L, 0.113 L/h, 0.123 L, 0.135/h, and 0.0135/h, respectively. Inter-individual variabilities were estimated and dose formulation （DF） was identified as a significant covariate of Ka 1, Ka0, and V1. It is concluded that the pharmacokinetic behaviors of paeoniflorin in rats can alter with different dose formulations.
