Abstract: AIM: To establish RIA method for determination of gestodene and aethinyloestradiol in blood serum, and investigate the pharmacokinetics and bioequivalence of compound gestodene tablet in Chinese healthy female adult volunteers. METHODS: Twenty-four female healthy volunteers were randomized to eceive a single crossover oral dose of compound gestodene reference tablet or domestic tablet. Seven mL venous blood was taken at time 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 6, 8, 12, 24, 36, 48, 72 h after administration. The concentrations of gestodene and aethinyloestradiol in blood serum were determined by RIA. The data were managed by DAS Software. RESULTS: The main pharmacokinetic parameters of test and reference compound gestodene tablets were as following :tmax of gestodene were (1.00 ±0.00) and (1.01 ±0.12)h ;their Cmax were (2756±287) and (2571±387) ng/L ;AUC0 -t were (23400 ±4288) and (26275±4609)ng/L_-1/h ;t_{1 2} were (13.1 ±1.6) and (14.5 ±2.2) h ;t_max of aethinyloestradiol were (1.54 ±0.25) and (1.75±0.25) h ;Cmax were (138 ±13) and (142 ±16) ng/L;AUC_0-t :were (2311±558 ) and (2266±637 )ng/L_-1/h ;t_{1 2β}were (28 ±7) and (31 ±8) h. The relative bioavailabilities of gestodene and aethinyloestradiol of test tablet were 88.97 % and 102.87 %. CONCLUSION: The assay method is shown to be sensitive and accurate giving reliable results. The test tablet was bioequivalent to the reference tablet.

Key words: compound gestodene tablet, gestodene, aethinyloestradiol, radioimmupoassay, pharmacokinetics, bioequivalence