iasepam 10mg was given by iv to 10 women with active phase inlabor and changes of cervicaldila tion were observed. The plasma concentration of diazepam and catecholamine level weremeasure by high performance liquid chromatography simultaneusly during labor. Thepharmacokinetics parameters were calculated with pharmacokinetic program 3p87.The resultsshowed that the distribution of plasma concentration of diazepam in laber women were twocompartment model and the pharmacokinetic parameters were t1/2α:3.17± 1. 2min; t1/2β:177. 8 ± 37.3min; Vd:2.44 ± 126;C 1:71.9±21.18ml/min respectively.The correlation anaysis between the plasma concentration of diazepma and its effect ondecreasing plasma catecholamin was positive correlation(y=3.69 ± 90.31x

r=0.86

P<0.05).Therewas significant difference between the diazepam group and ihe control(P<0. 01).This experunentbdicated that diazepam could dilatc cervix by decreasing plasma catecholamines.