THE BIOAVAILABILITY OF DESOGESTREL ETHINYL ESTRADIOL TABLETS RELATIVETO THE ORAL SOLUTION/

Two studies were conducted in randomised crossover designs to determin e the bioavailability of the tablet components of the 'desogestrel/eth inyl estradiol and ethinyl estradiol regimen (Mircette(TM))' relative to an oral solution. The desogestrel/ethinyl estradiol and ethinyl est radiol regimen (28 days) consists of the following treatment: 21 days of a 150 mu g desogestrel (DSG)/20 mu g ethinyl estradiol (EE) tablet; 2 days of a lactose/starch tablet (placebo); and 5 days of a 10 mu g EE tablet. In each study, 20 healthy women were enrolled, received at least one dose of test drug, and were included in the analysis of tole rability; however, only 18 subjects in each study completed both cross over periods and were included in the pharmacokinetic analysis. In stu dy 1, the women each received a total dose of 300 mu g DSG/40 mu g EE administered as two combination tablets or solution. The women each re ceived a total dose of 20 mu g EE administered as two tablets or solut ion in study 2. Serial blood samples were analysed by radioimunnoassay and pharmacokinetic parameters were estimated from the resulting seru m concentration-time profiles. The results of these studies demonstrat ed that the mean relative bioavailabilities of DSG (measured as 3-keto -DSG, the active metabolite of DSG) and EE from the combination tablet were 100% and 93%, respectively, and that of EE from the EE tablet wa s 99%. The difference in the extent of absorption for the combination tablet versus the reference solution was small; therefore the performa nce of both tablet formulations was near optimal. Both tablet formulat ions were generally well tolerated, with most of the adverse experienc es reported being transient and mild.