Abstract: A sensitive and specific method was developed for the isolation of puerarin from biological specimens and its quantitative determination by the application of polyamide thin layer chromatography and ultraviolet spectrophotometry. This method was adopted for the study of the metabolic fate of puerarin and its pharmacokinetics in rats, and also for the evaluation of drug elimination in humans.The blood level of puerarin following intravenous administration in rats was found to decrease in two phases, the distribution phase and the elimination phase, with halflives of 3 and 18 min respectively. The pharmacokinetic parameters calculated according to the 2-compartment open model were as follows:α=0.23/min β=0.04/minK₁₂=0.08/min V₁=19.9 mlK₂₁=0.09/min V₂=33.7 mlK_e(K₂)=0.1/min V_d=53.7 mlClearance=2.0 ml/minThese results imply that puerarin is distributed widely in the body and eliminated in a fairly rapid rate which prevelits its serious accumulation in the body.Determination. of the drug in various organs revealed that drug levels were highest in the kidney, moderate in plasma, liver and spleen and lowest in the brain, indicating the existence of a partial blood-brain barrier.Absorption of the drug from the gastrointestinal tract was found to be fairly rapid but incomplete, 37.7% of the close could still be recovered from the gastrointestinal content and the faeces 24 hours after administration:In rate, the amount excreted in urine and faeces within 24 hours was about 1.85% and 35.7% respectively of the dose. administered orally, as compared with 37.6% and 7.39% administered intravenously. In normal human volunteers, however, only 0.78% of the dose was found in urine in 36 hrs, and 73.3% of the dose was present in the faeces collected for 72 hrs after oral administration.In virto experiments provided evidence that puerarin was rather stable in the gastrointestinal tract, and might be metabolized by blood and various tissues such as liver, lung and kidney. The drug-plasma binding rate was found to be 24.6%.The metabolic characteristics of puerarin and daidzein were compared.