A non-chromatographic radioimmunoassay for 3-oxo desogestrel

The pharmacokinetics of ethynylestradiol in the presence and absence of gestodene and desogestrel

Single doses of ethynylestradiol (30 micrograms) were given alone and in combination with either gestodene (75 micrograms) or desogestrel (150 micrograms) to 10 healthy female volunteers. The doses of steroids were given both orally and by i.v. infusion over 5-7 minutes. Blood samples were taken at regular intervals over 24 hours. The area under the plasma concentration versus time curve (AUC) for oral EE2 alone was 867 +/- 338 pg/ml x h, for oral EE2 in the presence of gestodene it was 795 +/- 206 pg/ml x h and for oral EE2 in the presence of desogestrel it was 614 +/- 132 pg/ml x h. With either gestodene or desogestrel present, the AUC of EE2 was not significantly different from that found when EE2 was given alone. In addition, there was no significant difference between EE2 + gestodene and EE2 + desogestrel. Comparing the relative oral and iv doses, the bioavailability of EE2 (alone) was 59.0 +/- 13% (n = 6), for EE2 plus gestodene it was 62.1 +/- 10% and for EE2 in the presence of desogestrel it was 62.1 +/- 4.4%. The clearance of EE2 (alone) was 19.9 +/- 5.5 l/h and in the presence of gestodene it was 19.4 +/- 9.6 l/h. The clearance of EE2 in the presence of desogestrel appeared slightly greater at 27.7 +/- 8.9 l/h but none of these clearance values were significantly different from each other. The urinary excretion of 6-beta-hydroxy cortisol was similar after all 6 doses of EE2. These data strongly suggest that following single dose administration, neither gestodene nor desogestrel have any inhibitory effect on the metabolism of EE2 or alter its kinetics to any clinically significant extent.

Serum pharmacokinetics of orally administered desogestrel and binding of contraceptive progestogens to sex hormone-binding globulin

Serum levels of 3-ketodesogestrel and ethinyl estradiol were analyzed by radioimmunoassay in a balanced crossover study with two tablet formulations containing desogestrel (0.150 mg) and ethinyl estradiol (0.030 mg) in 25 women under steady-state conditions after 21 days of treatment. The pharmacokinetic properties of desogestrel were characterized by the following parameters: (1) maximum serum concentration, (2) time to maximum serum concentration, (3) total area under the serum concentration versus time curve, and (4) serum half-life of elimination. The interindividual variation in these parameters was comparable with that observed with other contraceptive combinations containing ethinyl estradiol and norethisterone, levonorgestrel, or gestodene. The serum distribution of contraceptive progestogens is known to be determined by their affinity to sex hormone-binding globulin and the concentration of sex hormone-binding globulin. We analyzed the structural features that determine binding to sex hormone-binding globulin. The 18-methyl group increased and the 11-methylene group weakened the binding to sex hormone-binding globulin. The double bond at C-15 reinforced the binding only when combined with an 18-methyl group. Therefore, the binding of levonorgestrel (the 18-methyl derivative of norethisterone) and gestodene (the delta-15,18 methyl derivative of norethisterone) to sex hormone-binding globulin was much stronger than that of 3-keto-desogestrel and norethisterone.

Serum levels of 3-keto-desogestrel and SHBG during 12 cycles of treatment with 30 micrograms ethinylestradiol and 150 micrograms desogestrel

The serum concentrations of 3-keto-desogestrel (KDG) have been determined radioimmunologically in 11 female volunteers on Day 1, 10, and 21 of the 1st, 3rd, 6th, and 12th cycle of treatment with 30 micrograms ethinylestradiol and 150 micrograms desogestrel during the first 4 hours and 24 hours after intake. On the first day of each cycle the KDG levels were low, but increased thereafter until Day 21. Highest serum concentrations were measured on Day 21 of the 3rd and 6th cycle with peak levels between 1.5 and 6.2 ng/ml. Contrary to this, the KDG levels were significantly reduced during the 12th treatment cycle. The serum concentrations of SHBG rose significantly between Day 1 and Day 21 of each cycle reaching values which were 3-fold of those at the beginning of treatment. During the pill-free intervals, SHBG levels decreased but remained elevated as compared to controls. There was a significant correlation between the SHBG levels and the area under the KDG-concentration-versus-time curves (AUC) indicating a pronounced influence of the serum steroid-binding protein upon the pharmacokinetics of KDG. There were great interindividual differences in the KDG levels. The serum levels of the individual woman remain, however, in a relatively constant range throughout the treatment period of 12 months, possibly due to genetic factors.

Plasma concentrations of 3-keto-desogestrel after oral administration of desogestrel and intravenous administration of 3-keto-desogestrel

The plasma concentrations of 3-keto-desogestrel have been measured by radioimmunoassay in a crossover study in nine healthy female volunteers given oral desogestrel (150 micrograms) and ethinyloestradiol (30 micrograms) and intravenous (i.v.) 3-keto-desogestrel (150 micrograms) and ethinyloestradiol (30 micrograms). Bioavailability ranged between 40.0 and 113% with a mean value ( +/- SD) of 76.1 +/- 22.5%. Only 3 subjects had a bioavailability of less than 70%. There was no significant difference in the elimination half life of 3-keto-desogestrel which was 12.6 +/- 4.1h following i.v. administration and 11.9 +/- 4.1h after oral administration of desogestrel.