Levels of Tibolone and Estradiol and their Nonsulfated and Sulfated Metabolites in Serum, Myometrium, and Vagina of Postmenopausal Women Following Treatment for 21 Days With Tibolone, Estradiol, or Estradiol Plus Medroxyprogestrone Acetate

Tibolone has estrogenic effects on the vagina but not on the uterus. To explain this, levels of tibolone and estradiol and their metabolites were determined in serum, myometrium, and vagina. Thirty-four postmenopausal women with uterine prolapse received either no treatment, tibolone, E(2) or E(2) + medroxyprogesterone acetate (MPA) for 21 days, or a single dose of tibolone. Twenty +/- 6 hours after administration, >98% of the 3-hydroxytibolone metabolites in serum and tissues were disulfated. Of the unconjugated metabolites, the estrogenic 3alpha-hydroxytibolone predominated in serum, whereas the progestagenic/ androgenic Delta(4)-tibolone predominated in myometrium and vagina. Levels of disulfated metabolites in serum and tissues were higher (3- to 5-fold) after multiple dosing than after a single dose. Tissue:serum ratios were <1, except for Delta(4)-tibolone. In all groups, E(2) tissue levels were higher than serum levels; the percentage of serum E(1)S was >90%. Tibolone did not affect endogenous E(1), E(2), or E(1)S levels in serum, but in myometrium and vagina, E(1) levels were significantly higher and E(1)S levels tended to be lower than in controls. Serum and tissue levels of endogenous and exogenous E(1), E(2), and E(1)S were markedly increased 20 hours after E(2) or E(2) + MPA; the percentage of E(1)S and tissue:serum ratios were not affected. MPA had no effect on the degree of sulfation of E(1). Compared with serum, tissue levels of E(2) were high in all groups; absolute E(2) levels in control and tibolone groups were much lower than in the E(2) groups. Tibolone metabolite patterns are different in serum, myometrium, and vagina.

Preparation and in vitro/in vivo evaluation of gestodene (GEST) intravaginal ring

Preparation and in vitro/in vivo evaluation of gestodene (GEST) intravaginal ring (IVR) formulations which can release a constant dose of GEST during 3 weeks were investigated. In present study a reservoir gestodene intravaginal ring, including a gestodene silicone elastomer core and the non-active silicone layer, was reported, which was manufactured by reaction injection moulding at 80°C for 20 min. The raw materials compatibility experiments showed that the silicone elastomer core carrier wouldn't interact with drugs. In vitro release samples were determined by HPLC and the experiment was performed under sink conditions. The equation of cumulative release verse time was Y=64.76χ+5.44 (r=0.9998), performing zero-order release at about the target dose of 60 µg/day over 21 days. Drug release increased with temperature elevating from 45 to 55°C, which could be attributed to optimizing the prescription. In addition, the pharmacokinetic and safety studies of gestodene intravaginal ring were evaluated in female New Zealand White rabbits. The GEST in plasma was analyzed by LC-MS/MS and the results proved that the correlation between in vitro and in vivo was relatively well.

[Simultaneous determination of gestodene, etonogestrel and ethinylestradiol in plasma by LC-MS/MS following derivatization]

To establish a sensitive and specific method for simultaneous determination of gestodene, etonogestrel and ethinylestradiol in plasma by LC-MS/MS, plasma samples were extracted and derivatized before injection. An ESI ion source was used and operated in the positive ion mode with multiple reaction monitoring (MRM). Norgestrel was chosen as internal standard and performed on a C18 (100 mm x 2.1 mm, 5 microm) column. The concentrations of gestodene, etonogestrel and ethinylestradiol were measured, using step-gradient mobile phase and step-gradient flow rate. The method was validated over the concentration range of 0.1-20 ng x mL(-1) for gestodene and etonogestrel and 0.01-2 ng x mL(-1) for ethinylestradiol, and showed excellent linearity. The intra- and inter-assay accuracy and precision were below 10.0% and recovery was 93.6%-110.9% over the three concentration levels evaluated. The method was applied in pharmacokinetic study of the compound gestodene patch and the compound etonogestrel patch in rabbits. The LC-MS/MS method was selective, accurate and sensitive, especially the LOQ were 100 pg x mL(-1) for gestodene and etonogestrel and 10 pg x mL(-1) for ethinylestradiol. The method was successfully applied in pharmacokinetic study for contraceptives.

The influence of smoking on uterine bleeding during sequential oral hormone therapy

OBJECTIVE

To study the influence of smoking on uterine bleeding patterns during sequentially administered oral hormone therapy (HT).

METHODS

Using a post-hoc strategy, we included four sequential oral HT groups from two studies. The therapies consisted of estradiol from days 1 to 28 (estradiol or estradiol valerate) and progestogen (levonorgestrel or gestodene) on days 17-28. A total of 111 healthy, early postmenopausal women (38 smokers and 73 non-smokers) followed for 2 years were included in the analyses. Uterine bleeding data were collected from bleeding calendars.

RESULTS

On the regimen containing levonorgestrel, smoking women had a cyclical bleeding significantly earlier than non-smoking women (about 2 days' difference). Moreover, smoking women had significantly longer bleeding than non-smoking women (about 1 day in difference). This was in contrast to the three regimens containing gestodene, where smoking seemed to have far less influence on uterine bleeding.

CONCLUSIONS

On a regimen containing levonorgestrel, smokers exhibit an earlier and longer uterine bleeding than do non-smokers. This is in contrast to regimens containing gestodene, where smoking women are less likely to differ from non-smoking women with regard to bleeding. This indicates that smoking influences progestogen metabolism, and that this influence may vary with different progestogens. Further studies are needed.

The growth-promoting action of individual women's sera on mammary carcinoma cells

In vitro studies concerning the growth-stimulating effect of hormones, especially of estradiol and its metabolites, have mainly been performed using pure substances and breast cancer cell lines. In order to take into account the metabolism of inactive into active hormones or drugs and vice versa which occurs in several tissues, the influence of individual patients' sera on the growth of breast cancer cells in vitro was tested. Besides measuring the growth promoting action of several hormone replacement therapies, the antiestrogenic effect was determined by measuring the effect of 10(-10) M estradiol added to the culture medium (E2-sensitivity). Influence on proliferation and stimulatability was similar in MCF-7 and T47-D cells. Growth-promoting potential correlated significantly with patient age, being higher in young ladies than in older ones. The converse was true for E2 sensitivity. From the different steroid hormones tested, only higher estradiol levels were associated with increased growth stimulation and diminished E2 sensitivity. Hormone replacement therapy (HRT) of different types did not significantly increase growth potential of serum, however these results are preliminary. Treatment with tamoxifen of breast cancer patients led to a decrease of E2 sensitivity, whereas growth potential was not affected significantly. For the aromatase inhibitor Arimidex, a tendency towards growth inhibition and increased E2 sensitivity was observed. Our in vitro system allows identifying differences between individual persons and groups of women of different age or treatment with respect to stimulation of growth or influence on estrogen sensitivity of breast cancer cells by serum. It is speculated that results might reflect the personal risk or the risk under treatment to develop breast cancer.

Estrogen and tibolone metabolite levels in blood and breast tissue of postmenopausal women recently diagnosed with early-stage breast cancer and treated with tibolone or placebo for 14 days

Unlike estrogens plus progestagens, tibolone, a selective tissue estrogenic activity regulator, does not increase breast tenderness and mammographic density. To elucidate this, serum and breast levels of tibolone and estrogenic metabolites are measured. Postmenopausal women (n = 102) with early-stage, ER(+ve), primary breast cancer received tibolone or placebo for 14 days in an exploratory, double-blind, randomized trial (STEM carcinoma tissue). Baseline and presurgery sera were collected; tumor tissues were obtained at surgery. E(1) (estrone), E(2) (estradiol), E(1)S (estrone-sulfate), tibolone-its nonsulfated, monosulfated, and disulfated 3-hydroxymetabolites-and Delta(4)-tibolone were measured by validated gas chromatography and mass spectrometry and liquid chromatography with tandem mass spectrometry assays. More than 12 hours after the final dose, serum E(1), E(2), and E(1)S levels were unchanged with placebo, whereas tibolone significantly increased E(1)S and the E(1)S/(E(1) + E(2)) ratio. In tumors, E(1) and E(2) levels were higher than in serum, and E(1)S levels were lower, with placebo and tibolone administration. The percentage of E(1)S was about 90% in serum and 16% in tissue. Tibolone did not affect tissue levels of endogenous estrogens. Serum levels of estrogenic 3alpha- and 3beta-hydroxytibolone, progestagenic/androgenic Delta(4)-tibolone, and monosulfate metabolites were low. Serum 3alphaS,17betaS-tibolone and 3 betaS,17betaS-tibolone levels were 250 and 52 ng/mL, respectively. Tumor levels of 3alpha- and 3beta-hydroxytibolone and Delta(4)-tibolone were higher than in serum, but disulfate levels were lower. The percentage of sulfated tibolone metabolites was 99% in serum and 96% in tumor. Serum metabolite patterns of estradiol and tibolone are different from those in tissues and are compatible with neutral effects of tibolone on breast Ki67 expression.

Selective tissue distribution of tibolone metabolites in mature ovariectomized female cynomolgus monkeys after multiple doses of tibolone

Tibolone is a selective tissue estrogenic activity regulator (STEAR). In postmenopausal women, it acts as an estrogen on brain, vagina, and bone, but not on endometrium and breast. Despite ample supporting in vitro data for tissue-selective actions, confirmative tissue levels of tibolone metabolites are not available. Therefore, we analyzed tibolone and metabolites in plasma and tissues from six ovariectomized cynomolgus monkeys that received tibolone (0.5 mg/kg/day by gavage) for 36 days and were necropsied at 1, 1.25, 2.25, 4, 6, and 24 h after the final dose. The plasma and tissue levels of active, nonsulfated (tibolone, 3alpha-hydroxytibolone, 3beta-hydroxytibolone, and Delta(4)-tibolone), monosulfated (3alpha-sulfate,17beta-hydroxytibolone and 3beta-sulfate,17beta-hydroxytibolone), and disulfated (3alpha,17beta-disulfated-tibolone and 3beta,17betaS-disulfated-tibolone) metabolites were measured by validated gas chromatography with mass spectrometry and liquid chromatography with tandem mass spectrometry. Detection limits were 0.1 to 0.5 ng/ml (plasma) and 0.5 to 2 ng/g (tissues). In brain tissues, estrogenic 3alpha-hydroxytibolone was predominant with 3 to 8 times higher levels than in plasma; levels of sulfated metabolites were low. In vaginal tissues, major nonsulfated metabolites were 3alpha-hydroxytibolone and the androgenic/progestagenic Delta(4)-tibolone; disulfated metabolites were predominant. Remarkably high levels of monosulfated metabolites were found in the proximal vagina. In endometrium, myometrium, and mammary glands, levels of 3-hydroxymetabolites were low and those of sulfated metabolites were high (about 98% disulfated). Delta(4)-Tibolone/3-hydroxytibolone ratios were 2 to 3 in endometrium, about equal in breast and proximal vagina, and 0.1 in plasma and brain. It is concluded that tibolone metabolites show a unique tissue-specific distribution pattern explaining the tissue effects in monkeys and the clinical effects in postmenopausal women.

Pharmacokinetic Parameters of Tibolone and Metabolites in Plasma, Urine, Feces, and Bile from Ovariectomized Cynomolgus Monkeys after a Single Dose or Multiple Doses of Tibolone

Levels of nonsulfated and sulfated tibolone metabolites were determined in plasma, urine, and feces from six ovariectomized, mature female cynomolgus monkeys after a single dose and multiple p.o. doses (including bile) of tibolone using validated gas chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry assays. In plasma, the predominant nonsulfated metabolite after single and multiple dosing was the estrogenic 3alpha-hydroxytibolone; levels of the estrogenic 3beta-hydroxytibolone were 10-fold lower and of progestagenic/androgenic Delta(4)-tibolone, 5-fold lower. Tibolone was undetectable. The predominant sulfated metabolite was 3alphaS,17betaS-tibolone; levels of 3betaS,17betaS-tibolone were about 2-fold lower, and monosulfated 3-hydroxymetabolites were about 10-fold lower. After multiple doses, areas under the curve of nonsulfated metabolites were lower (2-fold), and those of sulfated metabolites were 25% higher. In plasma, >95% metabolites were disulfated. In urine, levels of all the metabolites after single and multiple doses were low. After a single dose, high levels of 3beta-hydroxytibolone and the 3-monosulfated metabolites (3betaS,17betaOH-tibolone and 3alphaS,17betaOH-tibolone) were found in feces. After multiple dosing, 3alpha-hydroxytibolone increased, and the ratio of 3alpha/3beta-hydroxytibolone became about 1. The predominant sulfated metabolite was 3alphaS,17betaS-tibolone. Levels of all the metabolites in feces were higher after multiple doses than after a single dose. Levels of nonsulfated and 3-monosulfated metabolites were higher in feces than in plasma. Bile contained very high metabolite levels, except monosulfates. This may contribute to the metabolite content of the feces after multiple doses. 3beta-Hydroxytibolone and 3alphaS,17betaS-tibolone predominated. In conclusion, tibolone had different metabolite patterns in plasma, urine, feces, and bile in monkeys. The bile contributed to the metabolite pattern in feces after multiple doses. The major excretion route was in feces.

p-Toluenesulfonyl isocyanate as a novel derivatization reagent to enhance the electrospray ionization and its application in the determination of two stereo isomers of 3-hydroxyl-7-methyl-norethynodrel in plasma

In this paper, p-toluenesulfonyl isocyanate has been reported as a novel derivatization reagent with strong nuclephilic reactivity for the hydroxyl compounds. The derivatization for the two pharmacologically active 3-hydroxyl metabolites, 3alpha-hydroxyl-7-methyl-norethynodrel and 3beta-hydroxyl-7-methyl-norethynodrel by p-toluenesulfonyl isocyanate can be accomplished in 2 min under room temperature. The offline derivatization procedure introduced an easily ionizable sulfonylcarbamic ester moiety to the metabolites. This greatly improved the analyte's sensitivity in negative electrospray ionization and enabled us to achieve the desired lower limit of quantitation at 100 pg/ml in plasma. Therefore, a sensitive high performance liquid chromatography-mass spectrometry (HPLC-MS) method for the analysis of the two stereo isomers was developed. The method had been validated to be accurate, precise, and sensitive, and can be used for the metabolism pharmacokinetic study of tibolone in human subjects.

The in vivo metabolism of tibolone in animal species

The in vivo tissue distribution and metabolism of tibolone was studied in different animals to further investigate the compound's tissue-specificity. Tibolone's metabolism was studied in vivo in rats and rabbits by administration of [16-3H]-tibolone and the metabolic pattern was determined in urine and faeces after oral administration to female rats and dogs. The main excretory pathway was found to be excretion in the faeces. Important phase-I metabolic routes were the reduction of the 3-keto to the 3a- or 3beta-hydroxy functions with a preference for 3alpha-OH in rats and for 3beta-OH in dogs. To a lesser extent, hydroxylation reactions at C2 and C7, and a shift of the delta5(10)-double bond to a delta4(5)-position also occurred. The main phase-II metabolic route was sulphate conjugation of the hydroxyl groups at C3 and C17. Since the oxidation reactions form only a minor part of the metabolism of tibolone, it is concluded that the cytochrome P450 enzymes do not play an important role in tibolone's metabolism. For both phases, quantitative differences were found between the species. In human similar metabolites are found. Profiling of the target organs in female rats and rabbits showed a tissue-specific distribution of metabolites. The majority of the metabolites existed as sulphate conjugates and no glucuronidated conjugates were observed. The same metabolites were found in both the circulation and the tissues. However, different tissues had quantitatively different metabolic profiles.

Dose proportionality of three different doses of tibolone

STUDY OBJECTIVE

To assess dose proportionality of tibolone tablets after multiple oral administration.

DESIGN

Open-label, randomized, three-period crossover study

SETTING

Department of Drug Metabolism and Kinetics, N.V. Organon, Oss, The Netherlands.

SUBJECTS

Twenty-seven postmenopausal women aged 65 years or younger.

INTERVENTION

Subjects received tibolone 1.25, 2.5, or 5.0 mg once/day for 7 days.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of tibolone and its three primary metabolites were assayed. Steady state was attained by day 5. Elimination half-life for 3alpha-hydroxytibolone was 7.2-8.5 hours. At steady state, the dose-normalized peak concentration and area under the curve satisfied bioequivalence requirements for the 1.25- and 2.5-mg doses, but not fully for the 5.0-mg dose. Parameters were proportionally slightly lower for the 5.0-mg dose compared with the 1.25- and 2.5-mg doses.

CONCLUSION

Proportional bioequivalence was established for the 1.25- and 2.5-mg doses, but not between the 5.0-mg dose and the two lower doses of tibolone.

A comparison of tibolone and hormone replacement therapy on coronary artery and myocardial function in ovariectomized atherosclerotic monkeys

OBJECTIVE

Tibolone is used to prevent osteoporosis and to treat climacteric symptoms. The objectives of these studies were to measure and compare the effects of tibolone with hormone replacement therapy on coronary artery vascular reactivity and myocardial function and to relate these outcomes to treatment-induced plasma lipid/lipoprotein concentrations and atherosclerosis.

DESIGN

One hundred forty-eight adult ovariectomized cynomolgus monkeys were fed an atherogenic diet for 24 months while receiving one of five oral treatments: no treatment (control, n = 31); conjugated equine estrogens (CEE), given at the equivalent of 0.625 mg/day ( n = 27); CEE (same dose) plus medroxyprogesterone acetate (MPA), given at the equivalent of 2.5 mg/day ( n = 29); low-dose tibolone (LoTib; 0.625 mg/day equivalent, n = 30); or high-dose tibolone (HiTib; 2.5 mg/day equivalent, n = 31).

RESULTS

Quantitative coronary angiography showed that endothelium-mediated dilation was enhanced (17.5 +/- 5%, p = 0.002) in the CEE-treated group (but not other treatment groups) compared with the control. Both doses of tibolone and CEE reduced the incidence of dobutamine-induced ST-segment depression (LoTib: 33%, HiTib 25%, and CEE: 23%) compared to the control (79%) ( p = <0.05). Neither vascular reactivity nor dobutamine-induced myocardial ischemia were associated with treatment-induced changes in atherosclerosis or plasma lipid/lipoprotein concentrations.

CONCLUSIONS

Tibolone, unlike CEE, has no benefit for endothelium-mediated dilation. Despite these differences, both tibolone and CEE reduced the incidence of myocardial ischemia, whereas CEE+MPA had no effect. It is speculated that tibolone may have direct effects on the myocardium that protect against myocardial ischemia.

A comparison of tibolone and conjugated equine estrogens effects on coronary artery atherosclerosis and bone density of postmenopausal monkeys

This study compared the effects of tibolone, a tissue-specific compound for the treatment of climacteric symptoms and the prevention of osteoporosis, with those of conjugated equine estrogens (CEE) with and without medroxyprogesterone (MPA) on bone mineral density and coronary atherosclerosis (CAA) of postmenopausal cynomolgus monkeys. The groups were tibolone [two doses were used, 0.05 mg/kg (LoTib) and 0.2 mg/kg (HiTib)], CEE (0.042 mg/kg), CEE (0.042 mg/kg) plus MPA (0.167 mg/kg given continuously), and a control group given no treatment for 2 yr. Compared with no treatment, bone mineral density was higher by 6.3% (P = 0.0004) in the LoTib group and by 9.5% (P = 0.02) in the HiTib group compared with 4.3% (P = 0.12) for CEE and 4.5% (P = 0.10) for CEE+MPA. Plasma high density lipoprotein cholesterol was reduced by 49% with HiTib and by 34% with LoTib. There were no differences in CAA between control and HiTib (P = 0.60) or LoTib (P = 0.58). CEE and CEE+MPA both reduced CAA by about 62% (CEE vs. control, P = 0.02; CEE+MPA vs. control, P = 0.01). Despite adverse effects of tibolone on plasma lipoprotein concentrations, there was no increase in CAA, suggesting that tibolone is a cardiovascular-safe treatment for climacteric symptoms and the prevention of osteoporosis.

Charcoal treatment and risk of escape ovulation in oral contraceptive users

Ovulatory potential was studied during the use of two oral contraceptive pill preparations, after repeated mid-cycle administration of activated charcoal. Eleven women used monophasic pills containing gestodene, 75 microgram, plus ethinyl oestradiol, 30 microgram, or norethisterone acetate, 1 mg, plus ethinyl oestradiol, 30 microgram, for 4 months each, in randomized order. During both pill treatments the third cycle was a control cycle, and during the fourth cycle of both pill types, 5 g of activated charcoal was ingested four times a day, starting 3 h after pill intake, on cycle days 12, 13 and 14. Ovarian activity was monitored by intravaginal ultrasonography of follicles and by measurements of serum concentrations of LH, FSH, oestradiol and progesterone throughout the control and charcoal-treatment cycles of both pill treatments. None of the women ovulated. Follicular activity seen in two women did not correlate with charcoal administration. It is concluded that the possible enterohepatic recirculation of gestodene and norethisterone is not of clinical importance. Repeated charcoal treatment, when administered 3 h after but at least 12 h before pill intake, can be used to treat diarrhoea in women taking oral contraceptives.

Low doses of estradiol in combination with gestodene to prevent early postmenopausal bone loss

OBJECTIVE

Our purpose was to study combinations of estradiol and gestodene for prevention of bone loss in early postmenopausal women.

STUDY DESIGN

We randomly assigned 278 healthy, early postmenopausal women to receive either 2 mg 17beta-estradiol sequentially combined with 25 microg gestodene (group 2/25s), 2 mg estradiol sequentially combined with 50 microg gestodene (group 2/50s), 1 mg estradiol sequentially combined with 25 microg gestodene (group 1/25s), 1 mg estradiol continuously combined with 25 mg gestodene (group 1/25c), or placebo.

RESULTS

After 3 years the changes in bone mineral density of the spine were as follows (mean +/- SEM): group 2/25s, 7. 41% +/- 0.72%; group 2/50s, 8.53% +/- 0.90%; group 1.25s, 6.67% +/- 0.88%; group 1/25c, 4.44% +/- 0.59%; and placebo group, -2.03% +/- 0. 64%. The changes in bone mineral density were mirrored in the biochemical bone markers. The average responses for the urinary C-terminal telopeptide fragments of type I collagen corrected for creatinine excretion were as follows (mean of baseline +/- SEM): group 2/25s, -68.8% +/- 0.03%; group 2/50s, -72.8% +/- 0.02%; group 1/25s, -60.7% +/- 0.03%; group 1/25c, -52.28% +/- 0.04%; and placebo group, 6.5% +/- 0.09%. Beneficial lipid effects were found in all active groups. The decreases in low-density lipoprotein were as follows (mean +/- SEM): group 2/25s, -13.7% +/- 3.0%; group 2/50s, -14.6% +/- 3.2%; group 1/25s, -9.28% +/- 2.2%; group 1/25c, -9.92% +/- 2.4%; and placebo group, 1.53% +/- 1.9%.

CONCLUSION

These results demonstrate that estradiol therapy with 1 mg estradiol is fully protective against early postmenopausal bone loss.

Progestational effects of combinations of gestodene on the postmenopausal endometrium during hormone replacement therapy

OBJECTIVE

The aim of the study was to assess the dose-response effects on the postmenopausal endometrium of 3 sequential combined hormone replacement regimens and 1 continuous combined hormone replacement regimen of estradiol and gestodene.

STUDY DESIGN

In this 2-year double-blind, placebo-controlled study, 278 healthy postmenopausal women received either 2 mg estradiol sequentially combined with 50 microg or 25 microg gestodene, 1 mg estradiol sequentially or continuously combined with 25 microg gestodene, or placebo.

RESULTS

All 4 hormone treatment regimens produced a safe endometrial histologic appearance. The regimens that were based on the lower dose of 1 mg estradiol was associated with less uterine bleeding than were those that were based on 2 mg estradiol. For sequentially opposing the 2 mg dose of estradiol, the dose of 25 microg gestodene was less efficient in producing secretory activity than was the dose of 50 microg gestodene. The measurement of placental protein 14 in serum reflected the secretory transformation of the endometrial buildup.

CONCLUSION

The reduction in bleeding episodes associated with regimens with lower estradiol doses may lead to improved long-term therapy compliance by menopausal women. The potency of progestogens can be assessed by measuring the serum concentration of placental protein 14.

Effects of felbamate on the pharmacokinetics of a low-dose combination oral contraceptive

The effects of felbamate on the pharmacokinetics of a low-dose combination oral contraceptive containing 30 micrograms ethinyl estradiol and 75 micrograms gestodene were assessed in a randomized, double-blind, placebo-controlled parallel-group study in healthy premenopausal female volunteers established in a regimen of oral contraceptive use. They received either placebo or 2400 mg/day felbamate from midcycle (day 15) to midcycle (day 14) of two consecutive oral contraceptive cycles (months 1 and 2). Pharmacokinetic assessments of ethinyl estradiol and gestodene were performed on day 14 of both cycles. To determine whether ovulation occurred, plasma progesterone and urinary luteinizing hormone levels were measured, and diaries recording vaginal bleeding were kept. Felbamate treatment resulted in a significant 42% decrease in gestodene area under the plasma concentration-time curve (0 to 24 hours) (p = 0.018) compared with baseline, whereas a minor but not clinically relevant effect was observed on the pharmacokinetic parameters of ethinyl estradiol. There were no changes in the pharmacokinetics of ethinyl estradiol or gestodene after placebo treatment. No volunteer showed hormonal evidence of ovulation; however, one volunteer reported the onset of intermenstrual bleeding during felbamate treatment. Because of the effect of felbamate on the pharmacokinetics of gestodene and the report of intermenstrual bleeding, it is possible that the contraceptive efficacy of low-dose combination oral contraceptives may be adversely affected during felbamate treatment.

A single-dose and 3-month clinical-pharmacokinetic study with a new combination oral contraceptive

The study was performed in 14 young women. The combination oral contraceptive contained 75 microgram gestodene (GSD) and 20 microgram ethinyl estradiol (EE2) per dosage unit. The volunteers received a single dose on day 21 of a treatment-free precycle (PCd21) and, after a washout period of 7 days, used the preparation in a 21 d/7 d schedule for three months. Daily drug serum level profiles were taken on PCd21 and on days 1 and 21 of treatment cycles 1 and 3. In addition, trough drug serum levels were followed every other day during treatment cycles 1 and 3. Serum levels of GSD, EE2, CBG, SHBG and testosterone (T) were determined by means of specifically developed or commercially available RIAs. Pharmacokinetic evaluation was carried out with TOPFIT and parameters were evaluated for differences with the t-test. Main target variables were Cmax, tmax and AUC for EE2, GSD and unbound GSD on day 21, cycle 3 vs. PCd21. EE2 pharmacokinetics were in agreement with a dose of 20 microgram/unit. Single-dose Cmax of 65 pg/ml and AUC of 612 pg h ml(-1) increased by 40-60% during treatment cycles as a result of accumulation EE2 induced basal SHBG (102nmol/L) and CBG (42 microgram/ml) serum levels to about 220 nmol/L and 87 microgram/ml, respectively, at the end of treatment cycles 1 and 3. Serum T levels dropped to 50% of baseline levels during treatment cycles and free T concentrations were reduced by 60-70%. GSD pharmacokinetics at the end of treatment cycles 1 and 3 were different from single-dose pharmacokinetics. Single-dose Cmax of 3.5 ng/ml and AUC 0-24 h of 22 ng h ml(-1) increased to steady-state levels of 8-8.7 ng/ml and 90-106 ng h ml(-1), respectively. The increase in GSD levels under treatment is the result of two parallel processes, i.e. accumulation and enlargement of the specific binding compartment. This was shown by protein-binding experiments, demonstrating an increase in specific (SHBG) binding from 69% to 80% and a reduction in the free fraction of GSD by 40% during treatment. The results of GSD and EE2 pharmacokinetics obtained in the present study confirm previous results with Femodene, when the reduction in the EE2 dose by 10 microgram/d is taken into account.

Serum distribution of two contraceptive progestins: 3-ketodesogestrel and gestodene

A cross-over study of two oral contraceptive formulations, containing 30 micrograms ethinylestradiol in combination with 150 micrograms desogestrel (Marvelon) or 75 micrograms gestodene (Femovan), has been performed to compare the serum distribution and pharmacokinetics of gestodene and the active metabolite of desogestrel, namely 3-ketodesogestrel. Serum concentrations of both sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) were also measured and were increased more than 3-fold and 2-fold, respectively, on day 21 of the treatment cycle, with no statistically significant difference between treatment groups. In addition, 35 days after ingestion of either oral contraceptive had ceased, the serum SHBG and CBG concentrations were similar to the pretreatment values. During treatment cycles, increased serum SHBG levels were associated with a redistribution of 3-ketodesogestrel and gestodene such that the non-protein-bound (NPB) and albumin-bound fractions were reduced in concert with an increase in the relative proportions bound to SHBG. The proportion of gestodene bound to SHBG was consistently higher than that observed for 3-ketodesogestrel, and this undoubtedly reflects the higher affinity of SHBG for gestodene (Kd = 1.2 nM at 37 degrees C) when compared to 3-ketodesogestrel (Kd = 4.7 nM at 37 degrees C). It also probably accounts, in part, for the much higher total serum levels of gestodene (8.58 nmol/L) when compared to 3-ketodesogestrel (2.37 nmol/L) during the treatment cycles. Consequently, the absolute amounts of NPB, non-SHBG-bound, and SHBG-bound gestodene are significantly higher than those measured for 3-ketodesogestrel. It is concluded that ethinylestradiol-induced increases in serum SHBG levels during treatment with Marvelon or Femovan, influenced the distribution and total amount of 3-ketodesogestrel and gestodene in serum, respectively, and that this, combined with the higher affinity of SHBG for gestodene, results in a greater amount of bioavailable gestodene compared to 3-ketodesogestrel, despite the smaller dose of gestodene administered.

Pharmacokinetics and protein binding of 3-ketodesogestrel and gestodene in the serum of women during 6 cycles of treatment with two low dose oral contraceptives

The serum concentrations of 3-ketodesogestrel (KDG) and gestodene have been measured in 30 and 31 women respectively who took low dose oral contraceptives containing 30 micrograms ethinylestradiol together with either 150 micrograms desogestrel or 75 micrograms gestodene for 6 months. On days 1, 10 and 21 of the first third and sixth treatment cycles blood samples were drawn at 0, 0.5, 1, 1.5, 2, 3, 4 and 24 h. KDG and gestodene levels were measured by radioimmunoassays and were evaluated for Cmax (peak serum concentration), tmax (time to Cmax), and AUC (area under the curve) to 4 and 24 h. The overall total gestodene concentrations were higher and the accumulation of the steroid throughout a cycle greater than that of KDG. For example, the AUC0-4 of gestodene increased in cycle 1 by a factor of 2.8 (day 10 vs. day 1) and 3.6 (day 21 vs. day 1) compared to 2.3 and 2.6 for KDG. The higher concentration of gestodene reflects a lower volume of distribution than KDG, and is consistent with gestodene binding to sex hormone binding globulin (SHBG) with a higher affinity than KDG. Concentrations of KDG and gestodene were higher on day 1 of cycles 3 and 6 than on day 1 of cycle 1. The serum concentrations of KDG and gestodene during multiple dosing cannot be predicted on the basis of single dose pharmacokinetics.

Pharmacokinetics of gestodene and ethinylestradiol in 14 women during three months of treatment with a new tri-step combination oral contraceptive: serum protein binding of gestodene and influence of treatment on free and total testosterone levels in the serum

The pharmacokinetics of gestodene (GEST) and ethinylestradiol (EE2) were determined in 14 healthy women (age 18 to 32 years) during a treatment period of three months with a new tri-step combination oral contraceptive (Milvane). Prior to this treatment period, the same women received a single administration of a coated tablet containing 0.1 mg GEST together with 0.03 mg EE2. There was a wash-out phase of one week between both treatments. Following single dose administration, a mean terminal half-life of 18 h was observed for GEST. The total clearance was 0.9 ml x min-1 x kg-1 and the volume of distribution was 84 l. During a treatment cycle, GEST levels in the serum accumulated by a factor of 8 as compared to single dose administration. Steady-state drug levels were reached during the second half of each cycle. As compared to single dose administration, the following changes were observed for GEST at the end of treatment cycles one and three: prolonged terminal half-life (20 to 22 h), reduced total (0.16 ml x min-1 x kg-1) and free clearance (ca. 27 ml x min-1 x kg-1), reduced volume of distribution (ca. 18 l). A concomitant EE2-induced increase in the SHBG concentrations by a factor of three as compared to pretreatment values was observed during a treatment cycle and appeared to be mainly responsible for the changes in the pharmacokinetics of GEST. Marked changes were also seen for the serum protein binding of GEST. After single dose administration, the free fraction of GEST was 1.3% and the fractions bound to SHBG and albumin were 69.4% and 29.3%, respectively. At the end of cycle one, the free fraction was only 0.6% and the fractions bound to SHBG and albumin were 81.4% and 18.0%, respectively. There was no difference in corresponding pharmacokinetic parameters and in the serum protein binding of GEST at the end of cycles one and three. On the last day of treatment cycles one and three, the AUC(0-4h) values of EE2 were 299.2 and 278.1 pg x ml-1 x h, respectively, which corresponds to an about 30% increase as compared to single dose administration, where an AUC(0-4h) value of 216.1 pg x ml-1 x h was found. Total and free testosterone concentrations decreased during treatment cycles one and three by about 36% and 60%, respectively, compared with the corresponding values measured prior to treatment. The fraction of unbound testosterone thus decreased from 0.5% to 0.3% during treatment.

Pharmacokinetics and serum protein binding of gestodene and 3-keto-desogestrel in women after single oral administration of two different contraceptive formulations

Two low-dose oral contraceptives, both containing the same dose of ethinyl estradiol (EE2, CAS 57-63-6) but different progestins--gestodene (CAS 60282-87-3) and desogestrel (CAS 54024-22-5), respectively--were administered to 18 women in a single dose, cross-over study. The serum concentrations of gestodene (GEST, one of the components of Femovan) and 3-keto-desogestrel (KDG) have been measured by specific radioimmuno-assays and the pharmacokinetics of both progestins were assessed. The serum protein binding of both compounds was also investigated and although the free fraction was the same for GEST and KDG, the distribution with respect to the binding proteins albumin and sex hormone binding globulin (SHBG) was slightly different. GEST was mainly bound to SHBG, while KDG was predominantly bound to albumin. Maximum concentrations of GEST were observed after 0.7 +/- 0.2 h and amounted to 4.9 +/- 2.4 ng/ml. A biphasic pattern of disposition was observed, with half lives of 0.13 +/- 0.06 h and 14.6 +/- 4.2 h, respectively. The AUC was 32.9 +/- 18.3 ng.ml-1.h. For KDG, maximum serum levels of 1.7 +/- 0.8 ng/ml were observed 1.5 +/- 0.8 h post administration. Drug levels declined with half-lives of 0.5 +/- 0.2 h and 17.0 +/- 9.3 h, respectively, and the AUC was 15.2 +/- 10.9 ng.ml-1.h.

Clinical trial with 3-keto-desogestrel subdermal implants

The study was done to assess the clinical performance and in vivo steroid release rate of 3-keto-desogestrel subdermal implants designed to deliver 5 different doses of the progestin. Volunteers were healthy women of proven fertility who provided blood samples at scheduled intervals during treatment. No pregnancy occurred in 514 woman-months in users of implants delivering 30 and 40 micrograms per day of 3-keto-desogestrel. Three pregnancies, one ectopic, were observed in 109 woman-months recorded with implants delivering 20 micrograms per day or less. Ovulation was inhibited, as judged by depressed progesterone levels, in 57 of 59 (97%) blood samplings in women whose 3-keto-desogestrel plasma levels were greater than 0.28 nmol/L and in 39 of 75 (52%) of cases with lower levels. Users of 4 cm implants manufactured by The Population Council, New York, showed mean levels above 0.28 nmol/L until 18 months of use. Levels achieved with 4.4 cm implants manufactured by Organon, Oss, Holland, were less consistent. No changes were observed in the plasma lipoprotein pattern or clinical chemistry during treatment. The main complaint was the occurrence of bleeding irregularities, particularly with the lower doses. Ovarian cysts found during pelvic examination in 11 (22%) subjects disappeared spontaneously within 7-90 days. 3-keto-desogestrel implants releasing around 40 ug/day and providing plasma levels around 0.28 nmol/L afford efficient contraceptive protection.

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.

Pharmacokinetics of the contraceptive steroids levonorgestrel and gestodene after single and multiple oral administration to women

Little is known about the pharmacokinetics of the two progestins levonorgestrel and gestodene during long-term administration compared with single-dose pharmacokinetics. The predictive value of single-dose administration for the pharmacokinetic behavior of a progestin during long-term treatment was investigated for two triphasic oral contraceptives. One contained levonorgestrel and the other gestodene, each in combination with ethinyl estradiol. In eight Japanese women who received the levonorgestrel-containing formulation over a treatment cycle, steady-state trough levels of levonorgestrel were higher than those obtained by computer simulation based on single-dose administration. An analogous observation was made in a group of 10 white women who received the gestodene-containing formulation. A close correlation between gestodene and sex hormone-binding globulin concentrations was demonstrated for eight subjects; the other two patients already had initially high sex hormone-binding globulin levels. Ethinyl estradiol-induced production of sex hormone-binding globulin seems to be a major factor that contributes to the accumulation of the two progestins in the plasma. Computer simulation, based on single-dose pharmacokinetics, allows an estimation of this contribution.

Pharmacokinetics and pharmacodynamics of oral contraceptive steroids: factors influencing steroid metabolism

The time-dependent alterations in the serum concentrations of ethinyl estradiol, gestodene, and 3-keto-desogestrel during treatment with 30 micrograms of ethinyl estradiol + 75 micrograms of gestodene or 30 micrograms of ethinyl estradiol + 150 micrograms of desogestrel were investigated during 12 months. The levels of gestodene and 3-keto-desogestrel increased between days 1 and 21 of each cycle, reaching maximal levels during the third and sixth cycles. The serum concentrations of gestodene were fourfold to fivefold higher than those of 3-keto-desogestrel. The ethinyl estradiol levels increased significantly between days 1 and 10 during each cycle and were significantly higher by 70% during intake of ethinyl estradiol/gestodene compared with ethinyl estradiol/desogestrel, although the dose was identical. Intake of gestodene, in addition to 35 micrograms of ethinyl estradiol + 2 mg of cyproterone acetate, caused a rise in ethinyl estradiol levels. During treatment with ethinyl estradiol/gestodene and an additional 150 micrograms of levonorgestrel, there was a continuous increase in gestodene levels, although sex hormone-binding globulin level did not change. During treatment with 30 or 35 micrograms of ethinyl estradiol and 75 micrograms of gestodene, 150 micrograms of desogestrel, or 2 mg of cyproterone acetate, there were large intraindividual and interindividual variations in the steroid levels and ratios of estrogen: progestogen levels. There was no correlation with the occurrence of intermenstrual bleedings. It is concluded that ethinyl estradiol and nortestosterone derivatives may inhibit steroid-metabolizing enzymes in the liver, which results in a rise in the serum levels of contraceptive steroids. The cause of the large intraindividual variations is as yet unknown, but it is probably from changes in steroid metabolism.

Intra- and interindividual variations in contraceptive steroid levels during 12 treatment cycles: no relation to irregular bleedings

During one year of treatment with oral contraceptives containing 30 micrograms ethinylestradiol and 150 micrograms desogestrel (EE/DG) or 30 micrograms EE and 75 micrograms gestodene (EE/GSD), the serum concentrations of EE, 3-keto-desogestrel (KDG) and GSD were determined on day 1, 10 and 21 of the 1st, 3rd, 6th and 12th cycle. The areas under the time-versus-concentration curves were calculated from the levels before and 0.5, 1, 1.5, 2, 3, 4 and 24 hours after intake of a tablet. There were large intra- and interindividual variations both revealing coefficients of variation (C.V.) between 25% and 80% (EE),, 30% and 50% (KDG) and 30% and 65% (GSD). During each cycle, the EE levels increased significantly between day 1 and 10 by 70% on average reaching a steady-state, while the progestogen concentrations rose by 100% (KDG) and 150% (GSD) up to a steady-state between day 10 and 21. After reaching the steady-state, the C.V. were generally lower. The ratios between the levels of EE and the progestogens showed still higher variations indicating different influences on the estrogen and progestogen component. There was no correlation between the steroid levels and weight, height or age. In spite of the large intraindividual variations, most of the women showed a distinct pattern of the levels of EE and the progestogens throughout the year of treatment indicating a genetic or acquired predisposition. The difference in the average AUC of EE, KDG and GSD between the women was 300% at most. During the first cycle of treatment with EE/DG and EE/GSD, about half of the women recorded intermenstrual bleedings which decreased thereafter. There was no relation between the occurrence of irregular bleedings and the average serum levels of EE and the progestogens of the individual women, neither during the first cycle nor during the whole treatment period of 12 cycles. It is concluded that spottings or breakthrough bleedings during treatment with oral contraceptives are not dependent on a distinct pattern of the serum levels of EE and the progestogen.

Protein binding of active ingredients and comparison of serum ethinyl estradiol, sex hormone-binding globulin, corticosteroid-binding globulin, and cortisol levels in women using a combination of gestodene/ethinyl estradiol (Femovan) or a combination of desogestrel/ethinyl estradiol (Marvelon) and single-dose ethinyl estradiol bioequivalence from both oral contraceptives

Results from two clinical pharmacokinetic studies are given. The first study was an observational study in oral contraceptive users who took either a combination of gestodene and ethinyl estradiol (pill A, Femovan) or desogestrel and ethinyl estradiol (pill B, Marvelon). A total of 69 women (39 receiving pill A and 30 receiving pill B) were evaluated to determine serum ethinyl estradiol, sex hormone-binding globulin, corticosteroid-binding globulin, and cortisol levels. Samples were obtained on 1 day during the tenth to twenty-first days of pill intake. All women received the respective oral contraceptive for at least 3 months. The test power was such that an 80% difference of 1 standard deviation of each target variable would have been detected (alpha = 0.05; beta = 0.1). No statistically significant differences were found in sex hormone-binding globulin, corticosteroid-binding globulin, or cortisol serum levels between both groups. Time and height of maximum ethinyl estradiol levels were identical as was the area under the curves. Ex vivo protein-binding analysis of the progestins revealed a free portion of 0.6% for gestodene and 2.5% for 3-ketodesogestrel as the active metabolite of desogestrel. Sex hormone-binding globulin-bound portions were much higher for gestodene (75.3% +/- 9.1%) than for 3-ketodesogestrel (31.6% +/- 12%). The remaining fractions were bound to albumin. In a second study, ethinyl estradiol-bioequivalence from pills A and B was investigated in 18 women in a controlled, single-dose, randomized, crossover design. The area under the ethinyl estradiol serum levels were identical up to 4 hours after pill intake between both treatments. According to the relatively low variation in data in this group of women, a 10% difference in ethinyl estradiol-availability could have been detected. Both studies indicate that the pharmacokinetics of ethinyl estradiol were independent of the concomitantly administered progestin, that is, desogestel and gestodene.

Clinical and hormonal effects of two contraceptives: correlation to serum concentrations of levonorgestrel and gestodene

Two triphasic oral contraceptives containing gestodene (GES) (a new progestogen) and levonorgestrel (LNG) were compared with respect to contraceptive effect, cycle control, acceptability and side effects. The serum concentrations of ingested hormones were measured together with ovarian, pituitary, and some adrenal hormones, as well as sex hormone binding globulin (SHBG). The contraceptive effect and cycle control were good with both preparations, and there were only a few minor side effects. SHBG was elevated 2-fold in the LNG group and 3-fold in the GES group. The GES concentration in serum varied more than the LNG concentration, but with correction for variations in SHBG binding, less variability in actual GES and LNG concentrations was seen. Serum levels of FSH, LH, estradiol and progesterone were all depressed with both preparations. The depression was more marked in the GES group, despite lower progestogen ingestion and similar serum concentrations. Equal decreases were found in testosterone, androstenedione and dehydroepiandrosterone sulfate (DHEA-S) with both preparations.

Protein binding of the contraceptive steroids gestodene, 3-keto-desogestrel and ethinylestradiol in human serum

The protein binding of ethinylestradiol (EE2), gestodene (GEST) and 3-keto-desogestrel (KDG) has been determined by ultrafiltration in the serum of women who had either taken a gestodene (n = 37) or desogestrel (n = 28) containing oral contraceptive for a time period of at least 3 months. GEST and KDG were analyzed in individual serum pools whereas EE2 was repeatedly measured in two serum pools, each one representing one treatment group. The respective free fractions of the three steroids were 0.6 +/- 0.1% (GEST), 2.5 +/- 0.2% (KDG), 1.7 +/- 0.6% (EE2, in the gestodene-group) and 1.5 +/- 0.2% (EE2, in the desogestrel-group). EE2 was exclusively bound to albumin, whereas GEST and KDG were also bound to sex-hormone-binding globulin (SHBG). The distribution of the two progestins over the serum binding proteins was determined after heat-treatment of serum samples. For GEST, the contribution of albumin and SHBG was 24.1 +/- 9.1 and 75.3 +/- 9.1%, respectively and for KDG it was 65.9 +/- 11.9 and 31.6 +/- 12.0%, respectively. SHBG and corticosteroid-binding globulin (CBG) concentrations were measured in the serum samples obtained from both treatment groups. In the gestodene-group 180 +/- 61 nmol/l (SHBG) and 89 +/- 13 mg/l (CBG) were measured, the corresponding values in the desogestrel-group were 226 +/- 64 nmol/l (SHBG) and 93 +/- 14 mg/l (CBG). SHBG concentrations were correlated with the total concentration of GEST and its free fraction and a positive (r = 0.395) and negative (r = -0.491) correlation respectively was found. Only a weak negative correlation (r = -0.291) was found for SHBG and the free fraction of KDG in the serum. These data demonstrate that the three contraceptive steroids EE2, GEST and KDG were all bound extensively to serum proteins, however, with pronounced differences concerning their distribution over the various binding proteins.

Lipid metabolism and coagulation of two contraceptives: correlation to serum concentrations of levonorgestrel and gestodene

The effects of two triphasic oral contraceptives containing the same amount of ethinylestradiol (EE) in combination with levonorgestrel (LNG) or gestodene (GES), respectively, on lipid metabolism and coagulation were studied. Serum concentrations of GES and LNG were determined at the same time. Thirty-three healthy women were randomized into two groups receiving either of the preparations. Before treatment and in the 3rd and the 6th cycle, blood samples were drawn in the morning while subjects were still in bed to obtain basal conditions. HDL2-cholesterol decreased in the LNG group but was unchanged in the GES group, whereas apolipoprotein A1 increased in the GES but not in the LNG group. Antithrombin III decreased in the GES group but was unchanged in the LNG-treated women. Factor VII increased in both groups, but more in the GES group. It is concluded that GES has a positive influence on lipid metabolism, and has a slightly negative influence on coagulation but the latter is more likely to be without clinical relevance. The positive influence of GES compared to LNG on lipids is probably due to its lower androgenicity and not to differences in bioavailability.

The in vivo release characteristics of a multi-compartment vaginal ring releasing 3-keto-desogestrel

The results of a stage I study of a new vaginal ring releasing 3-keto-Desogestrel [3kDOG] is reported. The study design consisted of one study cycle, where the ring was used continuously for 21 days and then removed. Twenty healthy volunteers were randomly allocated to each of two study groups. On day 5 of the menstrual cycle, group A used a vaginal ring releasing 30 micrograms 3kDOG per 24 hours and group B used a 15 micrograms 3kDOG per 24 hours ring. After initial absorption of the 3kDOG a plateau phase was reached in 46 hours [group A] and 49 hours [group B]. On reaching the plateau phase, the overall decline in plasma levels during the 21 days of use was 5.24% for group A and 5.27% for group B. This represents a daily decline in plasma levels of 0.27% and 0.28% for the 30 micrograms and 15 micrograms per 24 hours rings, respectively. The plasma levels achieved by the rings were significantly different throughout (p = 0.011). On removal after 21 days, the mean removal half-life for both ring types was similar at 20.9 hours for group A and 21.1 hours for group B. It is concluded that the characteristics of the delivery system are worthy of further study as a potential means of contraception using 3kDOG delivered from a vaginal ring.

Single dose pharmacokinetics of gestodene in women after intravenous and oral administration

Six healthy female volunteers (age 25 - 39 years) received 75 micrograms gestodene intravenously followed by 3 oral administrations of 25, 75 and 125 micrograms gestodene together with 30 micrograms ethinylestradiol (EE2) in a cross-over design. Gestodene plasma levels were determined using a specific RIA. After intravenous administration, plasma gestodene concentrations decayed triphasically with mean half-lives of 0.16 h, 1.5 h and 10 hours. The area under the plasma level curve, the total plasma clearance and the volume of distribution (VZ) were as follows: AUC = 35 +/- 15 ng.h/ml, CL = 0.80 +/- 0.53 ml/min/kg, and VZ = 0.66 +/- 0.43 1/kg, respectively. After oral administration of all doses, maximum plasma levels of 1.0 (25 micrograms), 3.8 (75 micrograms) and 7.0 ng/ml (125 micrograms) were achieved between 1.4 and 1.9 hours after the intake. Post-maximum levels showed 2 disposition phases with half-lives of 1 and 12 - 14 hours. Absolute bioavailabilities were calculated as 87.5 +/- 17.5% (25 micrograms), 99.3 +/- 10.9% (75 micrograms) and 110.8 +/- 17.7% (125 micrograms) indicating that gestodene is completely absorbed and systemically available at all doses investigated.

Development and application of a radioimmunoassay of the new progestagen gestodene

A radioimmunoassay for the determination of gestodene (17-ethinyl-13-ethyl-17 beta-hydroxy-4,15-gonadien-3-one) in human plasma is described with regard to procedure, specificity, accuracy and reproducibility. Antiserum was raised against gestodene-3-O-(carboxymethyl)oxime-BSA in rabbits and [9,11-3H]-gestodene tracer was used with a specific radioactivity of 2.16 TBq/mmol. The final antiserum dilution was 1: 200,000. RIA was performed according to routine methods using diethylether plasma extracts and the charcoal separation technique. Cross-reactivity of antiserum with cortisol, 17 beta-estradiol, progesterone, testosterone and ethinylestradiol was less than 0.03%; levonorgestrel exhibited a 5% cross-reactivity. No cross-reactivity with metabolites of gestodene or ethinylestradiol was found. Accuracy and precision of the assay were tested using human plasma samples spiked with 1, 5 and 10 ng/ml gestodene. Accuracy was within 94 to 104% of the nominal values. Within-assay and between-assay coefficients of variation were in the range of 4.7-6.5% and 10.3-13.1%, resp. This RIA was used to follow plasma gestodene levels after single oral administration of 75 micrograms of gestodene combined with 30 micrograms ethinylestradiol as tablet and coated tablet in a cross-over design in 6 female test subjects. Plasma gestodene levels were equivalent after both treatments.

Alterations in the serum levels of gestodene and SHBG during 12 cycles of treatment with 30 micrograms ethinylestradiol and 75 micrograms gestodene

The serum concentrations of gestodene have been measured radioimmunologically in 11 female volunteers on Day 1, 10, and 21 of the 1st, 3rd, 6th, and 12th cycle of treatment with an oral contraceptive containing 30 micrograms ethinylestradiol and 75 micrograms gestodene during the first 4 hours and 24 hours after intake. During the 1st cycle the maximal gestodene levels increased from 2.1 to 6.2 ng/ml on Day 1 to values between 7.5 and 22.0 ng/ml on Day 21. During the 3rd and 6th treatment cycle the levels were still higher with maxima between 10.1 and 26.3 ng/ml, while during the 12th cycle the gestodene concentrations were slightly lower. The serum levels of SHBG rose significantly during intake of the pill up to values between 210 and 240 nmol/l on Day 21 of each cycle, and were reduced to a certain degree during the pill-free interval. The SHBG concentrations correlated closely with the area under the gestodene concentration-versus-time curves (AUC) indicating a pronounced influence of serum protein binding upon the pharmacokinetics of gestodene. The gestodene levels of the individual women remained relatively constant during the 12 treatment cycles, although great interindividual differences were found. It is concluded that the relatively high serum concentrations of gestodene are not only based on the binding to SHBG, but probably also on an impeded metabolism of gestodene.

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.

Serum levels of 3-keto-desogestrel after oral administration of desogestrel and 3-keto-desogestrel

In a cross-over study with orally administered desogestrel (0.150 mg) plus ethinyloestradiol (0.030 mg) and 3-keto-desogestrel (0.150 mg) plus ethinyloestradiol (0.030 mg) in ten women under steady-state conditions, the serum levels of 3-keto-desogestrel were monitored by radioimmunoassay. No statistically significant differences between treatment groups were found with respect to the areas under the curve of the serum levels versus time (AUC), peak heights and peak times. The individual AUCs for 3-keto-desogestrel after dosing with desogestrel (plus EE) or 3-keto-desogestrel (plus EE) show a similar degree of variation. The biotransformation of desogestrel into 3-keto-desogestrel is rapid and appears not to be limited by the metabolic capacity of the normal liver.

A non-chromatographic radioimmunoassay for 3-oxo desogestrel

A non-chromatographic radioimmunoassay for 3-oxo desogestrel (13 beta-ethyl-17-hydroxy-11-methylene-18,19-dinor-pregn-4-en-20-yn-3- one), the biologically-active metabolite of desogestrel (13 beta-ethyl-11-methylene-18,19-dinor-pregn-4-en-20-yn-17-ol), has been developed to facilitate studies of the pharmacokinetics of this steroid. The method uses an antiserum raised against levonorgestrel (13 beta-ethyl-17-hydroxy-18,19-dinor-pregn-4-en-20-yn-3-one). None of the steroids tested which showed significant cross-reactions are believed to be present in plasma after ingestion of desogestrel; furthermore, dilutions of standards and unknowns gave parallel responses in the assay. Intra- and inter-assay coefficients of variation were 12.9 and 11.8% respectively. The sensitivity of the assay was approx 0.02 ng/ml. The peak concentrations of 3-oxo desogestrel after a 150 micrograms dose of desogestrel in three subjects were between 0.48-0.71 ng/ml, and in two subjects 3-oxo desogestrel was still detectable 24 h after dosing.

Pharmacokinetic observations on ST-1435 administered subcutaneously and intravaginally

Plasma levels of ST-1435 were determined by radioimmunoassay in 36 women and three men during treatment with subdermal capsules releasing ST-1435. The total lengths of the capsules used were 180 mm, 90 mm, 30 mm, 15 mm and 7.5 mm. A linear correlation between the mean plasma concentrations of ST-1435 and capsule length was found during the treatment period studied. However, great interindividual variation in plasma levels of ST-1435 between study subjects having similar capsules was observed. In comparison with the mean plasma concentrations in the initial months, only less than half of these plasma concentrations of ST-1435 were measured after six months of treatment, which indicates a short lifetime for this contraceptive system. In two women the disappearance of ST-1435 from the circulation was studied by measuring ST-1435 concentrations in the plasma after removal of a contraceptive vaginal ring (CVR) releasing ST-1435. Triphasic disappearance curves of ST-1435 were found, with half-lives 0.7-1.0 h, 3.1-4.0 h, and 10.7.3-11.8 h.

Intestinal absorption of ST-1435 in rats

The intestinal absorption of a 19-norprogesterone (ST-1435) was studied in rats after an oral dose of 5 mg ST-1435/kg body weight. Blood samples were collected simultaneously from the portal vein and by cardiac puncture. Plasma ST-1435 concentrations were measured from the samples by radioimmunoassay (RIA). Chromatographic purification of ST-1435 in rat plasma revealed a metabolite cross-reacting in the RIA. A peak concentration of 240 ng ST-1435/ml was found in portal plasma 75 minutes after administration, indicating that the steroid is well absorbed from the small intestine. However, in spite of the relatively high dose used, the plasma concentrations of ST-1435 in the systemic circulation remained low and of short duration. Thus, it seems that ST-1435 in hepatic portal blood is extensively taken-up and metabolized by the liver, resulting in low plasma concentrations of ST-1435 in the systemic circulation when the steroid is administered orally. This is also supported by the observation that higher metabolite levels were found in systemic plasma than in portal plasma during the first 90 minutes after administration. This pronounced first-pass effect may also explain why in women oral administration of ST-1435 has failed to result in any biological effect.

Plasma levels of levonorgestrel, gestodene, norethisterone and cyproterone acetate on single-dose subcutaneous administration in oily solution in the rat, beagle and rhesus monkey

This report describes the pharmacokinetics of levonorgestrel, gestodene, norethisterone and cyproterone acetate following subcutaneous administration of oily solutions in the rat, beagle dog and rhesus monkey. The plasma levels of the progestogens were measured by means of specific radioimmunoassays. Half-lives calculated for the disposition process of a particular metabolically unchanged drug in plasma revealed marked differences in different animal species. Furthermore, comparison of the different progestogens showed large variations in this parameter in all the animal species. It became obvious that there are physico-chemical properties as well as metabolic rate limitations effecting the release and elimination of synthetic progestogens administered in oily solution. The results are compared with the half-lives of these progestogens administered intravenously as reported previously. A prolongation of half-life as a result of the depot effect of subcutaneous administration was demonstrated for all the progestogens in the rat, the beagle dog and the rhesus monkey.

Serum non-protein bound percentage and distribution of the progestin ST-1435: no effect of ST-1435 treatment on plasma SHBG and CBG binding capacities

The non-protein bound percentage of ST-1435 was measured by centrifugal ultrafiltration-dialysis in undiluted female serum at 37°C. It was found that as much as 13% of ST-1435 in serum is not bound to proteins. The results also show that the affinities of SHBG and CBG of ST-1435 are very low and that SHBG and CBG do not bind ST-1435 under physiological conditions in serum. We suggest that ST-1435 is bound mainly to serum albumin, and that the binding to that accounts for more than 87% of total serum ST-1435 concentrations. During the treatment period of 3 months, no change in SHBG or CBG binding levels was observed when ST-1435 was administered parenterally.

The lack of any interaction between ST-1435 and high affinity serum steroid binding proteins, and the very high percentage of non-protein bound ST-1435 in serum, probably explain its extremely high biological potency at the hypothalamic-pituitary level, when compared for example with d-norgestrel. For the same reason, practically all the ST-1435 in hepatic portal blood is probably taken-up and very rapidly metabolised by the liver. This may explain why oral administration of ST-1435 results in low and inadequate plasma concentrations for contraceptive purposes, while alternative parenteral routes of administration result in relatively much higher serum concentrations of the steroid. Finally, because ST-1435 does not bind to SHBG and CBG under physiological conditions, and does not change plasma SHBG and CBG binding capacities, ST-1435 treatment will not indirectly alter the amounts of endogeneous sex steroid hormones or their distribution in plasma. Therefore, side effects such as acne or hirsutism are unlikely to develop as a result of sustained administration of this potent progestin.

Terminal half-lives in plasma and bioavailability of norethisterone, levonorgestrel, cyproterone acetate and gestodene in rats, beagles and rhesus monkeys

Norethisterone, levonorgestrel, cyproterone acetate and gestodene have been used for a long time in oral contraception and other indications, or are in the process of development for such indications. However, very little is known concerning the bioavailability and plasma levels of unmetabolized gestagens in the animal species used for chronic toxicity testing and pharmacological investigation. In this study the gestagens were administered intravenously, subcutaneously and orally to rats, beagles and rhesus monkeys. The drug plasma levels were determined by specific radioimmunoassay. The half-life of the terminal disposition phase was calculated following intravenous administration, and the extent of bioavailability was determined from the area under the drug level curves following subcutaneous and oral administration. The terminal half-lives of a particular compound in different animal species differed considerably. Furthermore, comparison of the different gestagens showed large variations in this parameter in all the animal species. In addition, inter-animal species comparison of a particular substance, and comparison of different substances in a single species, also showed great differences in bioavailability. The results are compared with the corresponding parameters in man. This investigation illustrates the fundamental problems inherent in the extrapolation of the results of toxicity studies and pharmacological investigations in animals, to man. The best tolerance and the lowest degree of pharmacological effect seem to occur where the bioavailability of a gestagen is poor and its terminal half-life short.