[Pharmacokinetics of epostane in rats].

After rats were given (ig) epostane 50, 100 and 200 mg.kg-1, plasma concentrations of epostane were determined by HPLC. According to concentration versus time data, the pharmacokinetic model of epostane in all rats followed a pattern of one-compartment model. The pharmacokinetic parameters of the three doses were found to be as follows: Ka were 0.578 h-1, 0.553 h-1 and 0.439 h-1; K were 0.308 h-1, 0.282 h-1 and 0.224 h-1; T1/2 were 2.27 h, 2.54 h, 3.12 h and AUC were 786.89 micrograms.h.ml-1, 1644.43 micrograms.h.ml-1, and 3335.35 micrograms.h-1.ml-1 respectively. The tissue distribution of epostane in rats were as follows: highest in adrenal, liver, gastrointestinal tract, uterus and ovary; next in kidney, heart, brain, lung and spleen. The peak concentration times were about 3 h and comparable to plasma peak time. Plasma protein binding of epostane was determined by equilibrant dialysis of the plasma of rats given the drug and found that the degree of binding was not correlated with drug dosage under our experimental conditions. Little epostane was found in the bile, urine and feces. It appears that epostane might have undergone extensive biotransformation in the rat body.