[Pharmacokinetics and pharmacodynamics of huangqin tang in febrile rats].

The pharmacodynamic (PD) and pharmacokinetic (PK) properties of Huangqin Tang (HQT) were investigated in yeast-induced febrile rats. Blood sample and rectal temperature data of the rats were collected at different times after single oral administration of HQT at 20 g x kg(-1). The plasma concentrations of paeoniflorin, baicalin, wogonoside, baicalein, wogonin, oroxylin A, glycyrrhizic acid and glycyrrhetinic acid were quantified by a sensitive liquid chromatography-tandem mass spectrometric (LC-MS) method. The blood concentrations of PGE2, 1L-1β and TNF-α were detected by radioimmunoassay (RIA). All pharmacokinetic parameters were processed by non-compartmental analysis using WinNonlin software. The potential relationship between the mean concentration of eight constituents and the antifebrile efficacy was investigated by calculating Pearson correlation coefficients. It was found that HQT had significant antifebrile efficacy in yeast-induced febrile rats, but had no effect to normal rats. The antifebrile effect of HQT can be attributed to the inhibition of PGE2, 1L-1β and TNF-α. The constituents (baicalin, wogonoside, baicalein, wogonin, oroxylin A, glycyrrhizic acid and glycyrrhetinic acid) in febrile rats had delayed absorption and elimination, a longer residence time in the body, and higher C(max) and AUC than those in normal rats. Febrile condition could affect the pharmacokinetic behaviour of HQT in vivo; the flavonoids with the same backbone showed the similar fate in the body; baicalein and wogonin had a strong positive correlation (R > 0.66, P ≤ 0.02) with the antifebrile efficacy determined. Together, these constituents demonstrated different pharmacokinetic properties in the febrile body.