Influence of gestodene and desogestrel as components of low-dose oral contraceptives on the pharmacokinetics of ethinyl estradiol (EE2), on serum CBG and on urinary cortisol and 6 beta-hydroxycortisol

Abstract

A randomized controlled clinical trial was undertaken over a 6-month treatment period with two low-dose combined oral contraceptives (OC) to investigate whether the metabolism and elimination of ethinyl estradiol (EE2) is differently influenced by the two progestational components gestodene (G) and desogestrel (D), an issue which has been very controversial recently. The two formulations contained 30 micrograms EE2 each, together with either 75 micrograms G or 150 micrograms D. Of the 40 young women recruited for each formulation, 31 of each group were available for statistical evaluation. The pharmacokinetics of serum EE2 were studied on day 1, 10 and 21 of cycle 1, 3 and 6. There were no significant differences between the two groups in any cycle with respect to parameters measured. This was true for the distinct intracyclical rise in the mean EE2 serum levels from day 1 to day 10 and the smaller further increase between day 10 and day 21, with no change in this respect between the cycles studied. Respective changes were seen with regard to the area under the EE2 serum concentration curve up to 4 and 24 hours (AUC0-4 and AUC0-24), cmax and tmax of serum EE2. The estrogen-dependent corticoid-binding globulin (CBG) increased similarly in the two groups intracyclically and slightly also intercyclically at all times tested. Except for the first treatment cycle, urinary excretion of cortisol and 6 beta-hydroxycortisol displayed a tendency to lower values intracyclically as well as intercyclically, again with no differences between the two groups. Also, the 6 beta-hydroxycortisol-to-cortisol ratio was not different between the groups, showing a slight tendency to rise from about 4 at the beginning of the medication to around 5.5 at the end of the 6th treatment cycle in both groups. It is concluded that G and D as components of low-dose OCs exert comparable effects on the metabolism and elimination of EE2.

PIP: The question of whether the pharmacokinetics of ethinyl estradiol (EE2) is affected differently by the progestins in low-dose combined oral contraceptives containing gestodene or desogestrel was revisited. 80 randomly allocated women took 30 mcg EE2 and either 75 mcg gestodene or 150 mcg desogestrel for the first 21 days of each cycle for 6 months. Blood samples taken on days 1, 10, and 21 of the 1st, 3rd and 6th cycle, at frequent times for 24 hours after pill intake, were analyzed for EE2, corticosteroid binding globulin, cortisol and 6beta-hydroxycortisol. 31 women in each group completed the study. Minor side effects such as headache, breast tension, acne, and nausea occurred in each group; 1 subject dropped out because of headache, nausea, and hypermenorrhea and 1 because of a hematoma. No significant differences were seen in serum EE2 levels including the rise in mean EE2 on days 1-10, or the smaller rise between days 10-21, or the pharmacokinetic parameters Cmax, tmax, area under the curve (AUC) at 0-4 hours, or AUC at 0-24 hours. There was a maximal variation of 11% in intracyclical increases in serum EE2, but no change in intercyclical variations. There were also no significant differences between groups in the expected estrogen-induced increase in corticosteroid binding globulin. Urinary hydroxycortisol increased slightly over each cycle, somewhat more in the 1st cycle, and a bit more in the desogestrel cycles than in gestodene cycles, but not significantly. This study was contrasted in detail with the reports that prompted the controversy over pharmacokinetics of estradiol during intake of the involved combined pills. The import of the assays for cortisol metabolites is the fact that estradiol and cortisol are metabolized by the same liver cytochrome P450 isoenzyme.