Interaction with the pharmacokinetics of ethinylestradiol and progestogens contained in oral contraceptives

Drug Interactions Involving 17α-Ethinylestradiol: Considerations Beyond Cytochrome P450 3A Induction and Inhibition

It is widely acknowledged that drug-drug interactions (DDIs) involving estrogen (17α-ethinylestradiol (EE))-containing oral contraceptives (OCs) are important. Consequently, sponsors of new molecular entities (NMEs) often conduct clinical studies with priority given to OCs as victims of cytochrome P450 (CYP) 3A (CYP3A) induction and inhibition. Such scenarios are reflected in the US Food and Drug Administration-issued guidance documentation related to OC DDI studies. Although CYP3A is important, OCs such as EE are metabolized by sulfotransferase 1E1 and UDP-glucuronosyltransferase (UGT) 1A1, expressed in the gut and liver, and so both can also serve as loci of victim OC DDI. Therefore, for any NME, one should carefully consider its induction and inhibition profile involving CYP3A4/5, UGT1A1, and SULT1E1. As DDI perpetrators, available clinical DDI data indicate that EE-containing OCs can induce (e.g., UGT1A4 and CYP2A6) and inhibit (CYP1A2 ≥ CYP2C19 > CYP3A4/5 > CYP2C8, CYP2B6, CYP2D6, and CYP2C9) various CYP forms. Although available in vitro CYP inhibition data do not explain such a graded inhibitory effect in vivo, it is hypothesized that EE differentially modulates CYP expression via potent agonism of the estrogen receptor expressed in the gut and liver. From the standpoint of the NME as potential OC DDI victim, therefore, it is important to assess its projected (pre-phase I) or known therapeutic index and pharmacokinetic profile (fraction absorbed, absolute oral bioavailability, clearance/extraction class, fraction metabolized by CYP1A2, CYP2C19, CYP2A6, and UGT1A4). Such information can enable the prioritization, design, and interpretation of NME-OC DDI studies.

Reproducibility of hormone-driven regional grey matter volume changes in women using SPM8 and SPM12

Aim of this work was to evaluate the reproducibility of hormone driven regional grey matter volume differences in women, and their correlations with premenstrual symptoms, as determined by voxel-based morphometry (VBM). After data quality control, a total of 138 T1-weighted MR images were included in this longitudinal study, and were analyzed as three different subgroups. Women with a natural menstrual cycle were scanned at three time-points: follicular, ovulatory and luteal phase. Two groups of women, using androgenic and anti-androgenic hormonal contraceptives, respectively, were scanned twice: during the pill-free week and during pill intake. Additionally, subjects were asked to complete a "daily rating of severity of problems" questionnaire, to quantify premenstrual symptoms. All data were analyzed using SPM8 and SPM12 with identical parameter settings. In the natural menstrual cycle group, the regional grey matter volume of the insula is larger at ovulation, as compared to the luteal phase. Premenstrual symptoms correlate differently with regional grey matter volumes between women with a natural cycle and hormonal contraceptive users. Changes in hormonal environment can to various extents affect VBM findings in women. We suggest that researchers take these confounding factors into account while applying this technique, to avoid heterogeneity in data acquisition and to safeguard the sensitivity of findings. Additionally, we suggest validating the consistency of results using more than one software package.

Prefrontal GABA concentration changes in women-Influence of menstrual cycle phase, hormonal contraceptive use, and correlation with premenstrual symptoms

Prefrontal regions are involved in processing emotional stimuli and are a topic of interest in clinical and neurological research. Although sex steroids are potent neuromodulators, the influence of menstrual cycle phase and hormonal contraceptive use is rarely taken into account in neuroimaging studies. Our purpose was to evaluate changes in gamma-aminobutyric acid (GABA) in women, as measured by magnetic resonance spectroscopy (MRS), with phases of the menstrual cycle and use of hormonal contraceptives, and to assess correlations with premenstrual symptoms.Three MRI sessions per cycle were obtained in the natural cycle group, and two sessions in the hormonal contraceptives group. In addition to an anatomical scan, single voxel MRS in the prefrontal area was performed. After quality control, 10 women with natural cycle and 21 women taking hormonal contraceptives were included for analysis. Peripheral blood samples were obtained to determine endogenous hormone concentrations. Subjects were asked to complete a daily rating of severity of problems questionnaire, to quantify premenstrual symptoms. In the natural cycle group, we found a significant increase in prefrontal GABA concentration at the time of ovulation. Conversely, in the hormonal contraceptives group, no differences were found between the pill phase and pill-free phase. GABA concentrations did not significantly correlate with endogenous hormone levels, nor with premenstrual symptoms. Our results indicate that spectroscopically measured GABA concentrations are higher during ovulation in women with a natural menstrual cycle. We suggest that neuroimaging studies should take into account this variability.

Development and validation of UPLC-MS/MS method for simultaneous determination of gestodene and ethinyl estradiol in rat plasma

A selective and sensitive ultra-performance liquid chromatography method with tandem mass spectrometric detection for simultaneous determination of gestodene (GES) and ethinyl estradiol (EE) in rat plasma was developed and validated. GES, EE and the internal standard, norgestrel, were extracted with ethyl acetate, derivatized (EE only) with dansyl chloride and then back-extracted into diethyl ether-hexane (2:1, v/v). The separation was performed on an ACQUITY UPLC BEH C(18) column with gradient elution using mobile phase consisting of acetonitrile and water (both containing 0.1% formic acid). The detection was carried out by means of electrospray ionization (ESI) mass spectrometry in positive ion mode with multiple-reaction monitoring. Calibration curves of GES and EE were linear (r(2) >or= 0.99) over the concentration ranges 1.59-159 and 0.196-78.4 ng/mL, respectively. The intra- and inter-day precisions were not more than 6.9 and 12.9% for GES and 10.6 and 9.0% for EE, and the accuracies were -2.5-8.0% for GES, and -7.2-0.19% for EE, respectively. The method herein described was superior to previous methods and was applicable to the pharmacokinetic study of GES and EE in rats.

A comparative study on the effects of a contraceptive vaginal ring NuvaRing®and an oral contraceptive on carbohydrate metabolism and adrenal and thyroid function

OBJECTIVES

To compare carbohydrate metabolism, adrenal and thyroid function during use of a combined contraceptive vaginal ring (NuvaRing, NV Organon, Oss, The Netherlands) with those of a combined oral contraceptive.

METHODS

Healthy women aged 18-40 years used either the vaginal ring, delivering 15 microg ethinylestradiol and 120 microg of etonogestrel per day, or a combined oral contraceptive containing 30 microg ethinylestradiol and 150 microg levonorgestrel, for six cycles. Each cycle comprised 3 weeks of use of the ring or the pill followed by 1 ring- or pill-free week. The following parameters were measured at baseline and at the end of cycles 3 and 6: carbohydrate metabolism (glucose, insulin, glycosylated hemoglobin); adrenal function (total cortisol, cortisol binding globulin, dehydroepiandrosterone sulfate); thyroid function (thyroid stimulating hormone, free thyroxine).

RESULTS

Small and similar increases in insulin were seen in both groups. Concentrations of cortisol binding globulin and total cortisol rose significantly less during ring use than during combined oral contraceptive use (cycle 3, p= 0.0002; cycle 6, p < 0.0001). Levels of dehydroepiandrosterone sulfate did not change in either group. Thyroid stimulating hormone levels increased significantly more in the ring group at cycle 3 (p = 0.0016) but free thyroxine levels were unchanged in both groups.

CONCLUSIONS

Both the vaginal ring and the oral contraceptive have no clinically relevant effects on carbohydrate metabolism, adrenal or thyroid function.

Pharmacokinetic Drug Interactions Involving 17??-Ethinylestradiol

17alpha-Ethinylestradiol (EE) is widely used as the estrogenic component of oral contraceptives (OC). In vitro and in vivo metabolism studies indicate that EE is extensively metabolised, primarily via intestinal sulfation and hepatic oxidation, glucuronidation and sulfation. Cytochrome P450 (CYP)3A4-mediated EE 2-hydroxylation is the major pathway of oxidative metabolism of EE. For some time it has been known that inducers of drug-metabolising enzymes (such as the CYP3A4 inducer rifampicin [rifampin]) can lead to breakthrough bleeding and contraceptive failure. Conversely, inhibitors of drug-metabolising enzymes can give rise to elevated EE plasma concentrations and increased risks of vascular disease and hypertension. In vitro studies have also shown that EE inhibits a number of human CYP enzymes, such as CYP2C19, CYP3A4 and CYP2B6. Consequently, there are numerous reports in the literature describing EE-containing OC formulations as perpetrators of pharmacokinetic drug interactions. Because EE may participate in multiple pharmacokinetic drug interactions as either a victim or perpetrator, pharmaceutical companies routinely conduct clinical drug interaction studies with EE-containing OCs when evaluating new chemical entities in development. It is therefore critical to understand the mechanisms underlying these drug interactions. Such an understanding can enable the interpretation of clinical data and lead to a greater appreciation of the profile of the drug by physicians, clinicians and regulators. This article summarises what is known of the drug-metabolising enzymes and transporters governing the metabolism, disposition and excretion of EE. An effort is made to relate this information to known clinical drug-drug interactions. The inhibition and induction of drug-metabolising enzymes by EE is also reviewed.

Pharmacokinetics of chlormadinone acetate following single and multiple oral dosing of chlormadinone acetate (2 mg) and ethinylestradiol (0.03 mg) and elimination and clearance of a single dose of radiolabeled chlormadinone acetate

BACKGROUND

Published data on pharmacokinetic parameters for chlormadinone acetate (CMA) are in part contradictory, especially with regard to terminal half-life (t(1/2,z)).

MATERIALS AND METHODS

Single and multiple doses of CMA (2 mg) and ethinylestradiol (EE; 0.03 mg) were administered to healthy female volunteers for six menstrual cycles. Plasma concentrations of CMA and EE were determined by gas chromatography-mass spectrometry. Single-dose and steady-state pharmacokinetic parameters were calculated. In a separate study, healthy female volunteers were given a single 2-mg dose of radiolabeled CMA. Concentrations of radioactivity in fecal and urine samples were determined via liquid scintillation. Excretion of total radioactivity was calculated as percentage of administered dose.

RESULTS

Eighteen women completed the repeated-dose study. Peak plasma concentrations for CMA and EE were reached within 1 and 2 h after taking the study drug. Peak plasma concentrations of CMA were approximately 1600 pg/mL after single-dose administration and 2000 pg/mL after multiple dosing. CMA and EE showed linear pharmacokinetics throughout six cycles, with constant trough values of approximately 400-500 pg/mL for CMA and 20-40 pg/mL for EE. Mass balance factors were 1.2-1.4 for CMA and 1.6-1.7 for EE, and accumulation factors were 1.7-2 for CMA and 1.7-1.8 for EE. Mean t(1/2,z) of CMA was approximately 25 h after single dosing and 36-39 h at steady state. In the excretion balance study, mean dose of CMA recovered was 87.3+/-6.4%, with urinary and fecal excretion accounting for 45% and 42%, respectively.

CONCLUSIONS

The pharmacokinetics of CMA and EE is linear after multiple dosing and remains stable during long-term administration, once steady state is reached. The t(1/2,z) of CMA was 36-39 h after multiple dosing, which is considerably shorter than the 80 h often quoted in the literature.

Effect of a combined oral contraceptive containing 20 microg ethinyl estradiol and 75 microg gestodene on hemostatic parameters

The effects of a combined oral contraceptive (COC) containing 20 microg ethinyl estradiol (EE) and 75 microg gestodene (GSD) on prothrombin activity (PA), activated partial thromboplastin time (APTT), thrombin time (TT), platelet number, fibrinogen, antithrombin III (ATIII), protein C, protein S and D-dimer were evaluated over 6 months in 23 young, healthy women. Laboratory assessments were performed prior to initiation of COC use (pretreatment) and after 3 and 6 months of use. Results showed no significant changes in fibrinogen, protein C, ATIII or D-dimer during COC use, compared with pretreatment values. The increase in platelet count, decreases in protein S level, PA and APTT, and the prolongation of TT were significant. In conclusion, the use of a COC containing 20 microg EE and 75 microg GSD did not cause any significant changes in the hemostatic parameters studied that could be suggestive of a higher prothrombotic risk. Further studies with a larger sample size are necessary in order to obtain conclusive data.

Effect of ciclesonide and fluticasone on hypothalamic-pituitary-adrenal axis function in adults with mild-to-moderate persistent asthma

BACKGROUND

Despite their proven efficacy in the treatment and prevention of asthma exacerbations, current inhaled corticosteroids carry safety concerns, especially adrenal suppression. Ciclesonide (hydrofluoroalkane propellant) is a novel inhaled corticosteroid with few, if any, clinical adverse events.

OBJECTIVE

To evaluate the potential effects of ciclesonide therapy on the dynamic cortisol response to sequential low- and high-dose cosyntropin stimulation in adults with mild-to-moderate persistent asthma.

METHODS

This was a double-blind, randomized, placebo-controlled, 12-week study in adults with mild-to-moderate asthma. One hundred sixty-four patients were randomized and treated; 148 patients completed the study. Fluticasone propionate (chlorofluorocarbon propellant) was used as an active comparator. The doses administered were 320 microg of ciclesonide once daily, 320 microg of ciclesonide twice daily, and 440 microg of fluticasone propionate twice daily, all doses ex-actuator.

RESULTS

For both ciclesonide groups, changes in mean low- and high-dose peak serum cortisol levels and in 24-hour urinary free cortisol levels corrected for creatinine were small vs baseline and comparable with placebo. For the fluticasone propionate group, significant reductions vs placebo in serum cortisol levels in response to high-dose cosyntropin stimulation and in 24-hour urinary free cortisol levels were observed. Oral candidiasis rates were 2.5% for 320-microg/d ciclesonide, 2.4% for 640-microg/d ciclesonide, and 22.0% for 880-microg/d fluticasone propionate.

CONCLUSIONS

These findings confirm the safety of ciclesonide therapy, demonstrating that at doses up to 640 microg/d, the drug does not affect sensitive markers of adrenal function.

Long-Cycle Treatment with Oral Contraceptives

The conventional regimen of oral contraceptive (OC) use mimics the natural cycles by causing regular withdrawal bleeding, which can be avoided by omission of the hormone-free interval of 7 days. Consequently, long-cycle regimens with continuous administration of OCs for 3 or 6 months followed by a hormone-free interval of 7 days may reduce the frequency of menstruations and cycle-dependent complaints. Surveys have revealed that, despite a higher rate of irregular bleeding, the majority of women prefer the long-cycle regimen to the conventional OC regimen with regular bleeds every 4 weeks because it may improve quality of life. As this regimen increases the contraceptive efficacy to a large degree, continuous treatment with OCs may prevent unintended pregnancies in women who miss a pill or are concomitantly treated with drugs that are able to impair the efficacy of OCs. Postponement of withdrawal bleeding may also reduce or prevent menses-associated disorders such as hypermenorrhoea and dysmenorrhoea, and have beneficial effects in patients with haemorrhagic diathesis, endometriosis, uterine leiomyoma and polycystic ovary syndrome. Continuous use of OCs prevents the cyclic fluctuations of serum levels of ethinylestradiol and progestogen and, hence, the cyclic variations of metabolic serum parameters. Although the long-cycle regimen is initially associated with an elevated rate of irregular bleeding, the total number of bleeding days that require sanitary product protection is lower than during conventional OC treatment. Many physicians tend to prescribe extended OC cycles for postponement of menstruation or reduction of frequency of regular bleeding. This review summarises and examines the available data on OC long-cycle regimens. The data suggest that the rate of treatment-related side effects with OCs according to the long-cycle regimen is similar to that of conventional OC regimens. However, clinical trials are necessary to assess the impact of long-term OC long cycles on safety, particularly the risk of cancer and cardiovascular disease, and fertility after discontinuation of treatment.

Breast cancer and specific types of oral contraceptives: a large Norwegian cohort study

The aim of our study was to examine the risk of breast cancer according to specific types of estrogens and progestagens in oral contraceptives (OCs) based on the prospective Norwegian Women and Cancer study (NOWAC). Between 1991-97 women aged 30-70 years were drawn at random from the central person register and mailed an invitation and a questionnaire. Women (102,443) were enrolled with follow-up information collected throughout 1999 by linkage with national registries of cancer, mortality and emigration based on the unique national identification number. Among the 96,362 women included in the present analysis 851 invasive breast cancer were diagnosed. The adjusted risk of breast cancer increased with 25% for ever use of OCs and the risk increased with increasing duration of use (test for trend: p = 0.007). No association between time since last use and breast cancer risk was found after stratification on duration of use. Positive trend was still found for total duration of use among women who used OCs more than 5 years ago. Second generation of OCs had an increased risk with increasing duration of use. Classifying progestagens according to chemical groups, the relative risk increased significantly with increasing cumulative dose of levonorgestrel progestagen. It was difficult to conclude for the other groups due to lack of power. In a multivariate analysis the cumulative dose for all progestagen groups were non-significant, although we observed a significant increased risk with increasing milligram-months of estrogen exposure (p = 0.002). In conclusion, the increased risk of breast cancer related with OC formulations could be due mostly to estrogen component.

The effects of an oral contraceptive containing ethinyloestradiol and norgestrel on CYP3A activity

AIMS

To examine the effects of an oral contraceptive containing ethinyloestradiol and norgestrel on intestinal and hepatic CYP3A activity using midazolam as a probe substrate.

METHODS

In a nonblinded sequential study, nine healthy women received simultaneous doses of intravenous midazolam (0.05 mg kg(-1)) and oral 15N3-midazolam (3 mg) on days 0, 4, 6, 8, and 14. On study day 5, Ovral(50 microg ethinyloestradiol/500 microg norgestrel) was administered for 10 days. Serum and urine samples were assayed for midazolam, 15N3-midazolam and metabolites by liquid chromatography-mass spectrometry. A Digit Symbol Substitution Test (DSST) was used to assess changes in the pharmacodynamic activity of midazolam.

RESULTS

Moderate (% CV 26-46) interindividual variability in the pharmacokinetics of midazolam were observed. Compared with baseline, AUC(0,infinity)iv ratios (95% CIs) after 2, 4, and 10 days treatment with OC were 89% (79, 101), 96% (85, 109), and 88% (77, 99), respectively. The AUC(0,infinity)oral ratios (95% CIs) were 101% (82, 125), 105% (85, 130), and 114% (92, 141), respectively, after 2, 4, and 10 days OC treatment compared with baseline. Concomitant administration of the oral contraceptive, Ovral for 2, 4 or 10 days did not significantly alter the area under the curve, clearance, or half-life of midazolam after either oral or intravenous administration. No alterations in pharmacodynamic effects of midazolam were observed between treatment days. Mean DSST scores strongly correlated with mean total midazolam blood concentrations (r = -0.936).

CONCLUSIONS

Administration of Ovral for 10 days had no impact on intestinal or hepatic CYP3A activity as determined by midazolam metabolism.

Oral contraceptives and venous thromboembolic disease: the findings from database studies in the United Kingdom and Germany

OBJECTIVE

Three research articles published in late 1995 and early 1996 suggested that oral contraceptives containing either of the newer progestogens (gestodene or desogestrel) could be associated with an increased risk of venous thromboembolism. During the months after the initial publications, the results have been scrutinized with great care and further studies have been published. The findings of 2 recent database studies, 1 in the United Kingdom and 1 in Germany, are presented in this article.

PATTERNS OF USE

The average age of users of combined oral contraceptives in Germany was 27 years, compared with 26 years in the United Kingdom. In Germany the use of gestodene-based products was lower than that in the United Kingdom. In the United Kingdom the users of desogestrel with 20 microg ethinyl estradiol (Mercilon) were older than the users of desogestrel with 30 microg ethinyl estradiol (Marvelon).

CRUDE INCIDENCE

The crude incidence of venous thromboembolism in the UK study was 4.1 cases/10,000 woman-y exposure to combined oral contraceptives. In Germany it was 4.2 cases/10,000 woman-y. In Germany the rates among users of second-generation combined oral contraceptives were higher than those among users of third-generation products. The reverse was the case in the United Kingdom. In the United Kingdom the crude incidence rates were higher for the 20 microg estrogen desogestrel product than for the 30 microg product. CASE-CONTROL ANALYSIS: The adjusted odds ratios in the UK study did not show significant increases for desogestrel or gestodene compared with levonorgestrel products. There were inconsistencies in the results among centers in the 2 international studies (the World Health Organization and Transnational studies). In both there was a consistent inverse dose-response relationship with estrogen in all centers.

CONCLUSION

The limitations of the observational studies are such that the hypothesis that the newer progestogens are more likely to cause venous thromboembolism cannot be proved.

Role of cytochrome P450 enzymes in drug-drug interactions

Many adverse drug-drug interactions are attributable to pharmacokinetic problems and can be understood in terms of alterations of P450-catalyzed reactions. Much is now known about the human P450 enzymes and what they do, and it has been possible to apply this information to issues related to practical problems. A relatively small subset of the total number of human P450s appears to be responsible for a large fraction of the oxidation of drugs. The three major reasons for drug-drug interactions involving the P450s are induction, inhibition, and possibly stimulation, with inhibition appearing to be the most important in terms of known clinical problems. With the available knowledge of human P450s and reagents, it is possible to do in vitro experiments with drugs and make useful predictions. The results can be tested in vivo, again using assays based on our knowledge of human P450s. This approach has the capability of not only improving predictions about which drugs might show serious interaction problems, but also decreasing the number of in vivo interaction studies that must be performed. These approaches should improve with further refinement and technical advances.

Relationships of serum estradiol levels, menopausal duration, and mood during hormonal replacement therapy

A study was undertaken in 38 menopausal women on-cyclic HRT (estropipate) and estropipate + nor-ethindrone). Serum estradiol levels during treatment were related to mood changes and platelet MAO activity. The relationship between serum estradiol levels and mood changes was found to be a function of the duration of menopause. Women with a short duration of menopause (12.9 months +/- 6.1) were compared to women with a long duration of menopause (76.6 months +/- 52.3). Women with a short duration of menopause had significantly lower mean serum estradiol levels during HRT compared to women with a long duration of menopause (216.9 +/- 62.3 vs. 291.13 +/- 118.12, respectively, p < .02). It had previously been reported that estrogen treatment in menopausal women had a positive effect on mood, whereas the combination of estrogen plus a progestin had a negative effect on mood. We found that the women with a long duration of menopause and higher treatment serum estradiol levels had significantly more dysphoria when receiving a combination of estrogen plus progestin than did the women with a short duration of menopause and lower serum estradiol levels. However, both short and long duration menopausal groups showed improvement in mood when estrogen was administered alone. Platelet MAO levels, a marker of adrenergic and serotonergic function thought to relate to mood, were negatively correlated with serum estradiol levels during HRT. We suggest that these paradoxical findings may be secondary to a prolonged estrogen deficiency state in women with a long duration of menopause.

Modern oral contraceptives and cardiovascular disease

We reviewed evidence that bears on the cardiovascular safety of combined oral contraceptives containing second- and third-generation progestogens and < 50 micrograms of estrogen. Recent epidemiologic studies indicate that current use of these formulations is associated with a smaller increase in the incidence of venous thromboembolism than earlier formulations. In some studies the increase for third-generation formulations containing desogestrel or gestodene was about 1.5 to 2 times that for second-generation formulations, but there is evidence that differences between users in underlying risk and likelihood of being diagnosed contributed to this result. Recent studies of myocardial infarction suggest a smaller increase in risk associated with modern formulations than with earlier ones; one study suggests a threefold increase for second-generation formulations and no increase for third-generation formulations, but the finding requires confirmation. Recent studies of stroke indicate little or no increase in risk for modern formulations among women without risk factors. We conclude that modern combined oral contraceptives are safer than earlier formulations with respect to cardiovascular disease, which occurs rarely in young women.

Pharmacokinetics of the new progestogens and influence of gestodene and desogestrel on ethinylestradiol metabolism

The purpose of the present report is to summarize the most important pharmacokinetic features of the new progestogens. In addition, the question of whether or not gestodene, in comparison to desogestrel, has an influence on the pharmacokinetics of ethinylestradiol (EE2) will be addressed.

Oral contraceptives and venous thromboembolism

In October, 1995, the United Kingdom Committee on Safety of Medicines recommended that women should use oral contraceptives containing desogestrel or gestodene only if prepared to accept an increased risk of thromboembolism. This action was based on observational studies that indicated a 2-3-fold increase in the risk of thromboembolism when desogestrel and gestodene-containing contraceptives were compared to products with levonorgestrel. The fact that these studies point in the same direction is concerning, but it is possible that these observational studies, somewhat similar in design, are influenced by the same unrecognized biases. Furthermore, the case numbers are relatively small (20-40 cases), and, for example, preferential prescribing to women at greater risk could affect the results. It is difficult to reconcile the conclusions with the strong belief supported by good evidence that thrombosis is an estrogen dose-related complication, and that progestational agents have no impact on clotting parameters. In my view, these equivocal reports are not of sufficient strength to escape biases and to change our prescribing of oral contraceptives.

Third generation oral contraceptives and risk of venous thromboembolic disorders: an international case-control study. Transnational Research Group on Oral Contraceptives and the Health of Young Women

OBJECTIVE

To test whether use of combined oral contraceptives containing third generation progestogens is associated with altered risk of venous thromboembolism.

DESIGN

Matched case-control study.

SETTING

10 centres in Germany and United Kingdom.

SUBJECTS

Cases were 471 women aged 16-44 who had a venous thromboembolism. Controls were 1772 women (at least 3 controls per case) unaffected by venous thromboembolism who were matched with corresponding case for age and for hospital or community setting.

MAIN OUTCOME MEASURES

Odds ratios derived with stratified analyses and unconditional logistic regression to adjust for potential confounding variables.

RESULTS

Odds ratios (95% confidence intervals) for venous thromboembolism were: for any oral contraceptives versus no use, 4.0 (3.1 to 5.3); for second generation products (low dose ethinyl-oestradiol, no gestodene or desogestrel) versus no use, 3.2 (2.3 to 4.3); for third generation products (low dose ethinyloestradiol, gestodene or desogestrel) versus no use, 4.8 (3.4 to 6.7); for third generation products versus second generation products, 1.5 (1.1 to 2.1); for products containing gestodene versus second generation products, 1.5 (1.0 to 2.2); and for products containing desogestrel versus second generation products, 1.5 (1.1 to 2.2). Probability of death due to venous thromboembolism for women using third generation products is about 20 per million users per year, for women using second generation products it is about 14 per million users per year, and for non-users it is five per million per year.

CONCLUSIONS

Risk of venous thromboembolism was slightly increased in users of third generation oral contraceptives compared with users of second generation products.

Desogestrel, norgestimate, and gestodene: the newer progestins

OBJECTIVE

To review and compare the newer progestins desogestrel, norgestimate, and gestodene with regard to chemistry, pharmacokinetics, efficacy, and tolerability.

DATA SOURCES

Primary literature on desogestrel, norgestimate, and gestodene was identified from a comprehensive MEDLINE English-literature search from 1984 through 1994, with additional studies selected by review of the references. Indexing terms included progestins, desogestrel, gestodene, norgestimate, levonorgestrel, and norgestrel.

STUDY SELECTION

Only human clinical and pharmacokinetic trials performed in Europe, Canada, and the US were included.

DATA EXTRACTION

All available data from human studies were reviewed; both comparative and noncomparative studies were included because of the paucity of direct comparative information available.

DATA SYNTHESIS

The newer progestins were designed to minimize the adverse effects (e.g., acne, hirsuitism, nausea, carbohydrate and lipid metabolism changes) observed with older oral contraceptives (OCs) while maintaining efficacy and good menstrual cycle control. Desogestrel, norgestimate, and gestodene have minimal amounts of androgenicity and antiestrogenic potential. All of these agents are pharmacokinetically similar to older agents: they are highly bioavailable when administered orally, hepatically metabolized, and obtain steady-state concentrations after 8-10 days of continuous administration. The newer agents have similar Pearl Indexes and slightly better cycle control. Furthermore, the new progestins appear to cause fewer adverse effects, such as acne and hirsuitism, and similar rates of weight gain, blood pressure changes, and lipid and carbohydrate metabolism changes.

CONCLUSIONS

Desogestrel, norgestimate, and gestodene appear to offer clinical advantages because of their decreased androgenicity. Women whose cycles are currently well controlled with other OCs should not be switched to a newer progestin. However, any of the combination OC products that contain these progestins may be prescribed for women intolerant of older agents or to first-time users of OCs. The newer progestins appear to be efficacious and offer similar cycle control, improved safety and tolerability profiles, and comparable price with the older agents.

Sex steroids and lipoprotein metabolism

Lipoprotein metabolism is involved in atherogenesis. Female sex-hormones have substantial effects on both lipoprotein metabolism and the vessel wall. Cholesterol, one of the major lipids in lipoproteins, is both the substrate for, and the target of, the steroidal sex hormones.

Lansoprazole does not affect the bioavailability of oral contraceptives

The effects of the proton pump inhibitor lansoprazole on the bioavailability of a low-dose oral contraceptive (OC), containing 0.03 mg ethinyloestradiol (EE) and 0.15 mg levonorgestrel (LNG), were investigated. Twenty-four healthy females (aged 19-35 years; weight 60.6 +/- 7.1 kg) participated in a multiple-dose, placebo-controlled, randomized two-way cross-over study. All subjects received the OC over 2 full menstrual cycles from day 1 to day 21 separated by a drug-free interval of 7 days. Lansoprazole (60 mg day-1) or placebo was coadministered for 3 weeks each. Plasma concentrations of EE and LNG were determined by GC-MS. The 90% confidence intervals for ratios of Cmax and AUC after log transformation of both EE and LNG ranged between 91 and 111%, indicating that lansoprazole did not affect the bioavailability of EE and LNG.

Aromatization and hydrolysis of norethisterone-3-oxime in rabbit

Two pharmacologically active metabolites, norethisterone (NET) and ethinylestradiol (EE2), were detected by HPLC and HPLC-RIA methods in rabbit plasma following single i.v. and i.g. administration at a dose of 1 mg/20 microCi/kg of [3H]norethisterone-3-oxime (NETO). Approximately 48% (i.v. injection) and 91% (i.g. administration) of the NETO dose were hydrolyzed to NET. Although only 0.35% of the NETO dose was aromatized to EE2, due to its high estrogenic potency, EE2 might contribute to the overall pharmacological pattern of NETO in the rabbit.

New knowledge in the physiology of hormonal contraceptives

The present review addresses some of the new knowledge regarding the physiology and mechanisms of action of hormonal contraceptives. Specific topics that are discussed include oral contraceptives, intravaginal rings, long-term contraception, gonadotropin-releasing hormone agonists and antagonists, and antiprogestins. It has been shown that in combined oral contraceptives, lower doses of the new progestins (desogestrel, norgestimate, and gestodene) can be used to inhibit ovulation compared with norethindrone and levonorgestrel. In addition, lower doses of ethinyl estradiol are now used with progestins. Estrogen has been added to intravaginal rings containing levonorgestrel or norethindrone acetate to reduce frequency of bleeding. A new ring containing 3-keto-desogestrel is under evaluation. The use of subdermal implants containing levonorgestrel is currently a popular and highly effective method of long-term contraception. Studies show that gonadotropin-releasing hormone agonists and antagonists can provide ovarian suppression, and antiprogestins such as RU486 effectively block the midcycle gonadotropin surge. These and other novel methods of hormonal contraception are still years away from general use.

Pharmacokinetics of a triphasic oral contraceptive containing desogestrel and ethinyl estradiol

OBJECTIVE

To demonstrate that pharmacokinetic measurements were made at steady state. Subsequently, dose proportionality for desogestrel and ethinyl E2 kinetics were demonstrated.

DESIGN

Open-label, noncomparative study.

SETTING

Healthy volunteers in an academic research environment.

PARTICIPANTS

Twenty white women who were 19 to 32 years old were solicited via an advertisement. Nineteen of the 20 women completed the study.

INTERVENTIONS

Study medication consisted of three cycles of a triphasic oral contraceptive containing desogestrel and ethinyl E2. Blood samples were taken at baseline and during cycle 3 between -48 and 24 hours on days 1, 7, 14, and 21, with additional sampling times on day 21 at 48, 60, and 72 hours.

MAIN OUTCOME MEASURES

Serum concentrations of 3-keto-desogestrel and ethinyl E2.

RESULTS

Evaluation of the trough serum levels indicated that a steady state of 3-keto-desogestrel had been reached. Statistical analysis on the Cmax, area under the curve (AUC), and Css,min indicated dose proportionality for the administered desogestrel. Ethinyl E2 serum levels obtained at the same time points also reflected steady state levels and showed minimal variability. The statistical analysis on Cmax, AUC, Css,min, and Tmax indicated that the pharmacokinetics of ethinyl E2 on days 7, 14, and 21 were not statistically significantly different, indicating dose equivalency.

CONCLUSIONS

Steady state of 3-keto-desogestrel is reached after each of the three phases and the pharmacokinetics are dose proportional. After reaching steady state, the pharmacokinetics of ethinyl E2 remain constant over time.

New progestogens in oral contraception

The major developments in combined oral contraceptives (COCs) have been a reduction in the total dose of both the oestrogen and progestogen administered per cycle and the introduction of new progestogens which are claimed to be more 'selective' than the older ones. This review examines in detail the clinical efficacy of the new COCs, where possible in comparison with those containing levonorgestrel or norethisterone, and their pharmacological effect on carbohydrate and lipid metabolism, haematological factors, pituitary-ovarian function and serum protein and androgen concentrations. Based mainly on the pharmacological evidence, the newer COCs are an improvement over the older low-dose formulations and are clearly preferable to the high-dose ones. However, the older low-dose COCs, despite many years of use, have not resulted in a high incidence of adverse effects. The increasing use of the new COCs, as evidenced by their increasing market share throughout Europe, does indicate that they have been well accepted in clinical practice.

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.

Contraception in Germany: a review

In this paper studies on current contraceptive use and attitudes toward various contraceptive methods in Germany are reviewed. Both the former West and East Germany are considered. On the basis of the existing studies it is difficult to have a clear impression of which methods are currently used in both countries and how contraceptive practice developed over time, due to methodological differences between studies. Nevertheless, it can be concluded that use of reliable contraceptive methods is widespread in both East and West Germany. In this respect East Germany differs considerably from other previously communistic countries. Attitudes were mainly assessed in West Germany, and with respect to oral contraceptives and IUDs great concern appeared to exist regarding the safety of both methods. As far as oral contraceptives are concerned, selective mass media attention toward possible side-effects of oral contraceptives may have contributed to this situation.

Single- and multiple-dose pharmacokinetics of a low-dose oral contraceptive in women with chronic renal failure undergoing peritoneal dialysis

OBJECTIVE

Our purpose was to compare the pharmacokinetic parameters of oral administration of a 35 micrograms ethinyl estradiol, 1 mg norethindrone pill in peritoneal dialysis patients and normal women.

STUDY DESIGN

A single-dose study was performed with five patients and four controls, followed by a multiple-dose study with five subjects in each group. Pharmacokinetic parameters were calculated by noncompartmental analysis and statistical analysis performed with Mann-Whitney U testing.

RESULTS

There is no difference in the pharmacokinetic parameters for norethindrone in peritoneal dialysis patients compared with normal women. During multiple dosing an increased area under the concentration curve and decreased apparent oral clearance was observed for ethinyl estradiol in peritoneal dialysis patients compared with normal women.

CONCLUSION

Peritoneal dialysis patients have decreased apparent oral clearance of ethinyl estradiol, leading to slightly higher serum concentrations compared with women with normal renal function. The clearance of norethindrone is the same in peritoneal dialysis patients and normal women.

Effect of four combined oral contraceptives on blood pressure in the pill-free interval

OBJECTIVE

To evaluate blood pressure changes in the pill-free interval and from baseline among women taking four different low-dose monophasic oral contraceptives.

DESIGN

131 women were randomized to four different oral contraceptives. Pressures were obtained at baseline, at the end of treatment cycles and at the end of the 7 pill-free days, during 6 months of treatment. Pressures were obtained at 4 and 8 weeks after discontinuation. Group 1 received norethisterone acetate 1000 micrograms, group 2 received levonorgestrel 150 micrograms, group 3 received desogestrel 150 micrograms, and group 4 received gestodene 75 micrograms, all combined with ethinyloestradiol 30 micrograms.

RESULTS

All four groups showed an increase in pressure during treatment, with return to baseline levels four weeks after treatment. At the end of the pill-free interval, the readings did not differ significantly from on treatment except for women in Group 4, who experienced an increase in diastolic pressure.

CONCLUSIONS

Use of the four oral contraceptives was associated with a small increase in systolic and diastolic pressure. Whatever mechanism causes the increase is not entirely reversible by 7 days without treatment.

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

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.

Pharmacokinetics, hydrolysis and aromatisation of norethisterone-3-oxime in female cynomolgus monkey

Norethisterone-3-oxime (NETO) was administered to 3 female cynomolgus monkeys intragastrically and, after a wash-out period of 2-5 weeks, intravenously at a dose of 1 mg/kg. The radioactive dose of tritiated NETO was 20 microCi/kg for both treatments. For i.v. injection, a 30% propylene glycol/water solution and for i.g. administration an aqueous microcrystalline suspension was used. Excretion of radiolabel in urine and feces was followed for 5 days and plasma samples were obtained up to 2 days after administrations. In all samples (urine, feces and plasma) radioactivity was determined. Extracts from plasma samples were subjected to HPLC separation of drug and metabolites, as well as NETO and NET (metabolite of NETO after hydrolysis of the oxime group) levels were determined. In addition, EE2 (ethinylestradiol, A-ring aromatised metabolite of NET) levels were estimated using a specifically designed HPLC system for separation. Quantification of EE2 was achieved by radioimmunoassay (RIA) of specific eluate fractions. The results demonstrate that [3H]-NETO was absorbed completely at a dose level of 1 mg/kg, and excreted predominantly via the kidneys. A urinary to fecal excretion ratio of 1.5 (i.v.) or 1.0 (i.g.) was found. Renal excretion of total radiolabel proceeded with a half-life of about 0.8 (i.v.) or 1.1 (i.g.) days. Balances were incomplete, probably due to technical reasons. Orally administered NETO was highly bioavailable (84.0 +/- 16.9% of dose) but rapidly cleared from plasma (total clearance corresponded to 97% of plasma liver flow). The clearance from plasma is equivalent to the metabolic clearance because almost no unchanged NETO is excreted. Extensive metabolism of the parent drug was observed leading to at least two pharmacologically active metabolites (NET, EE2). The main progestogenic metabolite was NET reaching similar high plasma levels as NETO. EE2 turned out to be a metabolite of NETO and a conversion rate of below 0.5% of dose was estimated. However, due to its high estrogenic potency EE2 might contribute to the overall pharmacological pattern of NETO in the cynomolgus monkey.

P450 enzymes. Inhibition mechanisms, genetic regulation and effects of liver disease

Multiple hepatic P450 enzymes play an important role in the oxidative biotransformation of a vast number of structurally diverse drugs. As such, these enzymes are a major determinant of the pharmacokinetic behaviour of most therapeutic agents. There are several factors that influence P450 activity, either directly or at the level of enzyme regulation. Drug elimination is decreased and the incidence of drug interactions is increased when there is competition between 2 or more drugs for oxidation by the same P450 enzyme. The available knowledge concerning the relationship between the presence of certain functional groups within the drug structure and inhibition of P450 activity is increasing. In many instances, it is possible to associate inhibition with certain drug classes, e.g. antimycotic imidazoles and macrolide antibiotics. Disease states, especially those with hepatic involvement, and the genetic makeup of the individual are conditions in which some P450s may be downregulated (that is, the enzyme concentrations in liver are decreased), with associated slower rates of drug elimination. In these individuals, dosages of drugs that are substrates for downregulated P450s should be decreased. Exposure to environmental pollutants as well as a large number of lipophilic drugs can result in induction (upregulation) of P450 enzyme activity. This raises the issue of previous approaches to the study of P450 induction in vivo. The use of human hepatocyte preparations in culture is a promising new direction that could assist the determination of modifications to drug therapy necessitated by exposure to inducing agents. Until such information is obtained, however, the use of drugs known to increase the microsomal expression of particular P450s, and increase associated drug oxidation capacity in humans, should be used with caution.

Single and multiple administration of a new triphasic oral contraceptive to women: pharmacokinetics of ethinyl estradiol and free and total testosterone levels in serum

Ethinyl estradiol is part of almost every combined oral contraceptive, and its pharmacokinetic characteristics have been thoroughly investigated in numerous studies. However, little is known about its pharmacokinetics during long-term administration, as compared with single-dose administration. In this study 10 women received a triphasic formulation that contained ethinyl estradiol together with the progestin gestodene over one treatment cycle. Mean area under the curve values of ethinyl estradiol were significantly higher on the last treatment day, as compared with the corresponding values obtained from the same women after single-dose administration. However, the observed increase in area under the curve was within the range of pharmacokinetic accumulation, to be expected on the basis of dosing interval and terminal half-life. Another point of interest was the effect of the triphasic preparation on testosterone concentrations in serum. Both total and free testosterone levels were suppressed by about 60% as compared with pretreatment values, and there was no correlation with corresponding sex hormone-binding globulin levels in the serum.

Characteristics of the new progestogens in combination oral contraceptives

This review details the characteristic features of three new progestogens which soon will be available in low-dose combination oral contraceptive agents in the United States. Available data suggest that desogestrel, gestodene, and norgestimate are extremely potent progestogens with few androgenic side effects. The smaller changes in lipids induced by these progestogens seem to confer some advantage to the use of preparations containing one of these agents. Whether this advantage is also present clinically remains to be determined.

Intrasubject variability in the pharmacokinetics of ethynyloestradiol

Intrasubject and intersubject variability in the metabolism of ethynyloestradiol (EE) was assessed in a cross-over randomized study of 6 women who each received 3 months treatment with 50 micrograms EE and 50 micrograms EE with 250 micrograms levonorgestrel (LNG). Blood samples were collected at the end of each treatment month, assayed for EE and the half-life of elimination (Tel) and bioavailability (area under the serum concentration-time curve, AUC) calculated. Intrasubject variability for Tel and AUC varied markedly; the variability was random and not correlated with the formulation administered. The intrasubject variability for Tel and AUC was 31 and 17%, respectively, and intersubject variability 66 and 95%. The intersubject range of values was more than 3-fold for both Tel and AUC and the intrasubject range about 2-fold. The pharmacokinetics of EE were not influenced by LNG; mean values for Tel and AUC were 17.3 +/- 5.5 h and 11.1 +/- 3.8 ng/ml/h, respectively, when EE was administered alone compared with 16.4 +/- 4.8 h and 12.5 +/- 3.9 ng/ml/h when given with LNG. However, EE influenced the metabolism of LNG; Tel for LNG was 19.3 +/- 4.2 h when administered alone and significantly higher (30.0 +/- 11.2 h) when given with EE. There was no correlation between the rate of metabolism of EE and that of LNG. The intrasubject variability shown in this and other studies suggests that genetic factors are less important in intersubject variability than previously thought. Some implications of intrasubject variability are discussed.

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.

Effect of the progestogens, gestodene, 3-keto desogestrel, levonorgestrel, norethisterone and norgestimate on the oxidation of ethinyloestradiol and other substrates by human liver microsomes

A number of different progestogens, levonorgestrel (LNG), norethisterone (NET), gestodene (GSD), desogestrel (DG) and norgestimate (NORG) are used in combination with the oestrogen ethinyloestradiol (EE2) in oral contraceptive steroid preparations. All the progestogens are acetylenic steroids and previous studies have indicated the potential of acetylenic steroids to cause mechanism-based or "suicide" inactivation of cytochrome P-450. We have compared the effects of the different progestogens on EE2 2-hydroxylation (a reaction catalyzed by enzymes from the P-450IIC, P-450IIIA and P-450IIE gene families) and also the oxidative metabolism of other drug substrates (cyclosporin, diazepam, tolbutamide) by human liver microsomes. On coincubation with EE2 as substrate, GSD, 3-keto desogestrel (3-KD, the active metabolite of desogestrel) and LNG produced some concentration-dependent inhibition of EE2 2-hydroxylation (maximum 32% inhibition at 100 microM 3-keto desogestrel). Ki values determined for GSD and 3-KD were 98.5 +/- 12.3 and 93.2 +/- 10.3 microM (mean +/- SD; n = 4), respectively. Preincubation of progestogens in a small volume (50 microliters) incubation for 30 min in the presence of an NADPH-generating system enhanced the inhibitory potential of all the steroids (at 100 microM, inhibition was for GSD 39%, 3-KD 46%, LNG 46%, NET 51% and NORG 43%). Inhibitory effects were therefore comparable and also similar to the macrolide antibiotic troleandomycin. The most marked inhibition seen was of diazepam N-demethylation and hydroxylation by GSD (71 and 57%, respectively) and 3-KD (62 and 50%, respectively). In preincubation studies involving cyclosporin as the substrate, the order of inhibitory potency was GSD greater than 3-KD greater than NET greater than LNG for production of both metabolite M17 and M21. The results of the study indicate that all the progestogens in common use have the propensity to inhibit a number of oxidative pathways but there is little evidence for one progestogen being more markedly inhibitory than others.

Group comparison of serum ethinyl estradiol, SHBG and CBG levels in 83 women using two low-dose combination oral contraceptives for three months

Serum ethinyl estradiol (EE2), sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) concentrations were studied in healthy young women randomly allocated to one of two low-dose combination oral contraceptives containing 30 micrograms EE2 and either 75 micrograms gestodene (F) or 150 micrograms desogestrel (M) per unit. There was either no (formerly non-pill users) or one (pill users) wash-out cycle before the study started with a pill-free pretreatment cycle in which the hormone status and basal SHBG and CBG levels were measured. Treatment was for three months. During treatment cycles 1 and 3, there were three test days each. Seven serum samples were obtained up to four hours and one sample 24 hours after intake of the first, tenth and the last (21st) pill. Additional samples were taken prior to morning ingestion of pills 5 and 15. For each individual and each test day, a representative serum pool has been constructed for SHBG and CBG analysis. EE2 concentrations were analyzed in all individual samples by means of a specific and sensitive RIA using anti-EE2-6 beta-CMO-BSA antiserum. Area under the curves (AUC) up to 4 and 24 hours, Cmax and tmax were evaluated and compared between the two treatment groups (n = 40 for F, n = 43 for M). SHBG and CBG concentrations were measured using commercially available immunoassay kits. Groups were large enough to detect a difference in group means of 75% of one standard deviation (alpha = 0.05, 1-beta = 0.9) of target variables, which is equivalent to 28 pg EE2/ml for Cmax, 69 pg.h.ml-1 for AUCEE2 0-4h, 257 pg.h.ml-1 for AUCEE2 0-24h, 39 nmol/l SHBG and 13.4 micrograms CBG/ml. Results clearly demonstrate that there were no differences between the two treatment groups in any of the target variables at any of the six test days distributed over a three-month period. Mean SHBG and CBG pretreatment levels of about 70 nmol/l and 37 micrograms/ml, respectively, increased to about 210 nmol/l and 88 micrograms/ml during the first treatment cycle and to about 230 nmol/l and 93 micrograms/ml during the third treatment cycle. Whereas the time of maximum EE2 serum levels did not differ significantly between test days, Cmax, AUCEE2 0-4h and AUCEE2 0-24h values increased by 30-35% or 40-50%, respectively, when test days 10 and 21 were compared to test day 1. Similar results were found for the third treatment cycle.(ABSTRACT TRUNCATED AT 400 WORDS)

Interactions with oral contraceptives

The interaction of a range of different factors with the pharmacologic activity of oral contraceptives is reviewed. Pharmacokinetic interactions with oral contraceptives may occur (1) during absorption and extrahepatic circulation, (2) by interfering with protein binding, and (3) during hepatic metabolism. The hepatic mixed function oxidase system, which is mainly responsible for the metabolism of oral contraceptives, is affected by several different factors and is easily induced. Nutrition affects the activity of many drugs, but information regarding oral contraceptives is meager. Both pharmacokinetic and pharmacodynamic interactions, which may be synergistic or antagonistic, between the estrogen and gestagen components of oral contraceptives, are important, but there is no correlation between the rate of metabolism of the two components. Evidence suggests that some anticonvulsant, antibiotic, and antibacterial drugs may reduce the efficacy of oral contraceptives. Instances of interactions of other therapeutic agents are reported infrequently. The incidence of serious interactions is low and does not appear to have been reduced with low-dose oral contraceptives, probably because of large intersubject variability in the pharmacokinetics of oral contraceptives.