Serum distribution of the major metabolites of norgestimate in relation to its pharmacological properties

Clinical pharmacology of progestins

INTRODUCTION

In this paper, we report general pharmacological profile and major biological activities of natural progesterone (P) and progestins. The aim of this article consists of synthesizing the principal aspects of pharmacology and metabolism of P and progestins related to the clinical consequences of their use.

METHODS

We review scientific literature on the topic "Progestins", evaluating the most relevant data from original articles, reviews and meta-analyses.

EVIDENCE SYNTHESIS

Progestins represent a specific class of synthetic analogues of P clinically employed (alone or associated with estrogens) to manage several gynaecological conditions, for instance multiple abortions, luteal phase defect, premenstrual syndrome, abnormal uterine bleeding, endometriosis and menopause (for hormone replacement therapy). Besides their use in the field of contraception, many non-contraceptive benefits of estroprogestins are mostly due to the activities of progestins. Pharmacological characteristics, dosage and individual metabolism could be listed among the principal aspects influencing their clinical effects.

CONCLUSIONS

The choice of each progestin according to its pharmacological profile is crucial for the appropriate management of any gynaecological condition. An aware knowledge of these compounds is fundamental to hone medical practice.

Pharmacokinetics, metabolism and serum concentrations of progestins used in contraception

Many different forms of hormonal contraception are used by millions of women worldwide. These contraceptives differ in the dose and type of synthetic progestogenic compound (progestin) used, as well as the route of administration and whether or not they contain estrogenic compounds. There is an increasing awareness that different forms of contraception and different progestins have different side-effect profiles, in particular their cardiovascular effects, effects on reproductive cancers and susceptibility to infectious diseases. There is a need to develop new methods to suit different needs and with minimal risks, especially in under-resourced areas. This requires a better understanding of the pharmacokinetics, metabolism, serum and tissue concentrations of progestins used in contraception as well as the biological activities of progestins and their metabolites via steroid receptors. Here we review the current knowledge on these topics and identify the research gaps. We show that there is a paucity of research on most of these topics for most progestins. We find that major impediments to clear conclusions on these topics include a lack of standardized methodologies, comparisons between non-parallel clinical studies and variability of data on serum concentrations between and within studies. The latter is most likely due, at least in part, to differences in intrinsic characteristics of participants. The review highlights the importance of insight on these topics in order to provide the best contraceptive options to women with minimal risks.

Pharmacokinetic and Pharmacodynamic Profiles of Ethinylestradiol/Norgestimate Combination or Norethindrone upon Coadministration with Elagolix 150 mg Once Daily in Healthy Premenopausal Women

Background

Two pharmacokinetic/pharmacodynamic studies were conducted to evaluate the potential drug–drug interaction between elagolix, an oral gonadotropin-releasing hormone receptor antagonist, and an oral contraceptive (ethinylestradiol [EE] 0.035 mg and norgestimate 0.18/0.215/0.25 mg) or progestin-only contraceptive (norethindrone 0.35 mg) in healthy premenopausal women.

Methods

These phase I studies used a two-period, sequential design, where period 1 included treatment with oral contraceptives, followed by period 2 with contraceptives coadministered with elagolix 150 mg once daily.

Results

In study 1, pharmacokinetic exposures for EE in period 2 increased by 30% and the norgestimate metabolites decreased by approximately 15% when coadministered with elagolix. Mean hormone exposure appeared lower for follicle-stimulating hormone (FSH; 31%), luteinizing hormone (LH; 38%), and estradiol (E2; 16%). The percentage of women with consecutive progesterone (P) concentrations above 5 nmol/L was similar in both periods. Norethindrone pharmacokinetic exposures were comparable in both periods. The hormone exposure for LH and FSH was similar, and mean E2 exposure was 32% lower in period 2. The percentage of subjects with consecutive ovulatory P concentrations was also similar in both periods (study 2). Safety and tolerability profiles were unremarkable in both studies.

Conclusions

Coadministration of elagolix 150 mg once daily with oral contraceptives containing EE and norgestimate, or norethindrone, resulted in small pharmacokinetic changes in the oral contraceptive components. Similar or lower FSH, LH, and E2 exposures were observed during coadministration, with ovulatory P concentrations also comparable in both periods. The pharmacodynamic profiles of the oral contraceptives were maintained when coadministered with elagolix.

A Multi-Center, Open-Label, Pharmacokinetic Drug Interaction Study of Erenumab and a Combined Oral Contraceptive in Healthy Females

BACKGROUND

Erenumab is a human anti-calcitonin gene-related peptide monoclonal antibody developed for migraine prevention. Migraine predominately affects women of childbearing age; thus, it is important to determine potential drug-drug interactions between a common oral contraceptive and drugs used to treat migraine.

OBJECTIVES

We sought to evaluate potential drug-drug interactions between erenumab and a common oral contraceptive.

METHODS

Healthy women received three cycles of a norgestimate/ethinyl estradiol-containing oral contraceptive with a single 140-mg subcutaneous dose of erenumab during cycle three. Norgestimate metabolites (norgestrel and norelgestromin) and ethinyl estradiol pharmacokinetics were evaluated in the absence and presence of erenumab. Primary endpoint was peak plasma concentration (C_max) and area under concentration-time curve from time 0 to 24 h (AUC_tau). Luteinizing hormone, follicle-stimulating hormone, and progesterone concentrations were evaluated as pharmacodynamic markers.

RESULTS

Erenumab did not influence the pharmacokinetics of norelgestromin, norgestrel, or ethinyl estradiol. Least-squares mean estimates (90% confidence interval) for C_max ratios were 1.05 (0.90-1.23), 1.06 (0.97-1.16), and 1.04 (0.88-1.22) for norelgestromin, norgestrel, and ethinyl estradiol, respectively. Respective AUC_tau ratios were 1.02 (0.94-1.12), 1.03 (0.96-1.10), and 1.02 (0.91-1.14). Luteinizing hormone, follicle-stimulating hormone, and progesterone concentrations were similar after exposure to oral contraceptive alone and with erenumab.

CONCLUSION

Erenumab did not alter the pharmacokinetics of the active components of an estrogen/progestin combination oral contraceptive. Thus, no change in contraceptive efficacy is expected with erenumab.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02792517.

The Drug-Drug Interaction Potential of Antiviral Agents for the Treatment of Chronic Hepatitis C Infection

Several safe and highly effective direct-acting antiviral (DAA) drugs for chronic hepatitis C virus (HCV) have been developed and greatly increase the number of therapeutic options available to successfully treat HCV infection. However, because treatment regimens contain at least two drugs (e.g., elbasvir and grazoprevir, glecaprevir and pibrentasvir, or sofosbuvir with daclatasvir, simeprevir, ledipasvir, or velpatasvir) and up to five drugs (ombitasvir/paritaprevir/ritonavir plus dasabuvir with or without ribavirin), the potential for drug-drug interactions (DDIs) becomes an important consideration for HCV-infected individuals with comorbidities that require concomitant medications, such as human immunodeficiency virus/HCV coinfection or immunosuppression after liver transplantation. This review details the pharmacokinetics and DDI potential of approved DAAs for the treatment of HCV infection.

Contraceptive Care of Obese Women

Importance

In the United States, 27% of reproductive-aged women are overweight, and 35% are obese. Until recently, contraceptive research excluded women greater than 130% of their ideal body weight. Gaps in data limit evidence-based decision making for effective contraceptive counseling and management in this rapidly growing population.

Objectives

The aims of this summary are to review the benefits, adverse effects, and risk factors associated with contraceptive methods in obese women, with special attention to effectiveness, and provide contraceptive management and counseling recommendations for best clinical practice.

Evidence Acquisition

We performed a thorough search of PubMed for current literature, including original research articles, review articles, and guidelines on contraceptive counseling and management in obese women in the United States. We reviewed the body of evidence with special attention to studies published since recent Cochrane and systematic reviews on this topic.

Conclusions

Contraceptive use is safer than pregnancy, especially for obese women who have increased pregnancy risks. Baseline health is compromised by obesity, but contraceptive risks remain low. Long-acting, reversible contraceptive methods offer superior effectiveness, minimal risk, and numerous noncontraceptive benefits across body mass index groups. No substantial evidence supports ineffectiveness of any method in obese women except oral emergency contraception and the patch. Pharmacokinetic changes of obesity associated with other oral methods do not seem to result in clinically significant declines in effectiveness. Future contraceptive efficacy studies should include obese women to better discuss their contraceptive needs.

Relevance

This review is beneficial for all providers caring for reproductive-aged women wanting to avoid unintended pregnancy.

Combined hormonal contraception and the risk of venous thromboembolism: a guideline

While venous thromboembolism (VTE) is rare in young women of reproductive age, combined oral contraceptives increase the risk of VTE. In the patient in whom combined hormonal contraception is appropriate, it is reasonable to use any currently available preparation.

Hormonal contraception and obesity

The rising rate of overweight and obesity is a public health crisis in the United States and increasingly around the globe. Rates of contraceptive use are similar among women of all weights, but because contraceptive development studies historically excluded women over 130% of ideal body weight, patients and providers have a gap in understanding of contraceptive efficacy for obese and overweight women. Because of a range of drug metabolism alterations in obesity, there is biologic plausibility for changes in hormonal contraception effectiveness in obese women. However, these pharmacokinetic changes are not linearly related to body mass index or weight, and it is unknown what degree of obesity begins to affect pharmacokinetic or pharmacodynamics processes. Overall, most studies of higher quality do not demonstrate a difference in oral contraceptive pill effectiveness in obese compared with non-obese women. However, data are scant for women in the highest categories of obesity, and differences by progestin type are incompletely understood. Effectiveness of most non-oral contraceptives does not seem to be compromised in obesity. Exceptions to this include the combined hormonal patch and oral levonorgestrel emergency contraception, which may have lower rates of effectiveness in obese women. The purpose of this review is to summarize evidence on contraceptive use in women with obesity, including differences in steroid hormone metabolism, contraceptive effectiveness, and safety, compared with women of normal weight or body mass index using the same methods.

Molecular action of norgestimate: new developments

BACKGROUND

Acne occurs because the sebaceous glands are overstimulated by high levels of androgens or are hypersensitive to normal levels of testosterone. In women with mild or moderate acne, the association of norgestimate (NG), and ethinyl estradiol (EE) is an effective treatment. This is related to the effect of oral contraceptives on androgen production and transport and the antiandrogenic properties of NG itself.

DESIGN

The present work was undertaken to find out whether NG and its derivative, 17-deacetylnorgestimate(dNG), present steroid activities other than antiandrogen activities, using human progesterone receptor(PR), estrogen receptor α(ERα) and β(ERβ), glucocorticoid receptor(GR) and mineralocorticoid receptor(MR)-responsive cell lines.

RESULTS

We confirmed that NG and its metabolite were progestogen partial agonists (EC50 of 13 and 11.1 nM) and ERα selective agonists (EC50 of 30.4 and 43.4 nM), as well as full antagonists of low affinity for GR (IC50 of 325 and 255 nM) and moderate affinity for MR (IC50 of 81.2 and 83.7).

CONCLUSION

We demonstrated that NG and dNG have full progestogen and weak estrogenic (through ERα) properties, which could explain in part the efficacy of NG in association with EE for the treatment of moderate acne in women. Moreover, their antagonist MR activity might have a favorable impact on cardiovascular risk, atherosclerosis and lipid profiles.

Quantification of 17-desacetyl norgestimate in human plasma by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and its application to bioequivalence study

A rapid and sensitive ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) method was developed and validated for the estimation of 17-desacetyl norgestimate in human plasma using solid-phase extraction technique. 17-desacetyl norgestimate D6 was used as the internal standard. Simple gradient chromatographic conditions and mass spectrometric detection enabled accurate and precise measurement of 17-desacetyl norgestimate at sub-picogram levels. The proposed method was validated for a linear range of 20–5000 pg/mL with a correlation coefficient ≥0.9988. The intra-run and inter-run precision and accuracy were within 10%. The overall recoveries for 17-desacetyl norgestimate and 17-desacetyl norgestimate D6 were 96.30% and 93.90%, respectively. The total run time was 4.5 min. The developed method was applied for the determination of the pharmacokinetic parameters of 17-desacetyl norgestimate following a single oral administration of a norgestimate and ethinyl estradiol 0.250 mg/0.035 mg tablets in 35 healthy female volunteers.

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Simple and rapid estimation of norgestimate metabolite in human plasma.

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Sensitive method for 17-desetyl norgestimate estimation with limit of quantification 20 pg/mL.

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Better cleanup using solid phase extraction method.

Epidemiology of hormonal contraceptives-related venous thromboembolism

For many years, it has been well documented that combined hormonal contraceptives increase the risk of venous thromboembolism (VTE). The third-generation pill use (desogestrel or gestodene (GSD)) is associated with an increased VTE risk as compared with second-generation (levonorgestrel) pill use. Other progestins such as drospirenone or cyproterone acetate combined with ethinyl-estradiol (EE) have been investigated. Most studies have reported a significant increased VTE risk among users of these combined oral contraceptives (COCs) when compared with users of second-generation pills. Non-oral combined hormonal contraception, such as the transdermal patch and the vaginal ring, is also available. Current data support that these routes of administration are more thrombogenic than second-generation pills. These results are consistent with the biological evidence of coagulation activation. Overall, the estrogenic potency of each hormonal contraceptive depending on both EE doses and progestin molecule explains the level of thrombotic risk. Some studies have shown a similar increased VTE risk among users of COCs containing norgestimate (NGM) as compared with users of second-generation pill. However, for this combination, biological data, based on quantitative assessment of sex hormone-binding globulin or haemostasis parameters, are not in agreement with these epidemiological results. Similarly, the VTE risk associated with low doses of EE and GSD is not biologically plausible. In conclusion, newer generation formulations of hormonal contraceptives as well as non-oral hormonal contraceptives seem to be more thrombogenic than second-generation hormonal contraceptives. Further studies are needed to conclude on the combinations containing NGM or low doses of EE associated with GSD.

The effect of combined oral contraception on testosterone levels in healthy women: a systematic review and meta-analysis

BACKGROUND; Combined oral contraceptives (COCs) reduce levels of androgen, especially testosterone (T), by inhibiting ovarian and adrenal androgen synthesis and by increasing levels of sex hormone-binding globulin (SHBG). Although this suppressive effect has been investigated by numerous studies over many years, to our knowledge no systematic review concerning this issue had been performed. This systematic review and meta-analysis was performed to evaluate the effect of COCs on concentrations of total T, free T and SHBG in healthy women and to evaluate differences between the various types of COCs (e.g. estrogen dose, type of progestin) and the assays used to assess total T and free T.

METHODS

A review of the literature was performed using database searches (MEDLINE, EMBASE and the Cochrane Central Register of Clinical Trials) and all publications (from inception date until July 2012) investigating the effect of COCs on androgen levels in healthy women were considered eligible for selection. Three reviewers were involved in study selection, data extraction and critical appraisal. For the meta-analysis, data on total T, free T and SHBG were extracted and combined using random effects analysis. Additional subgroup analyses were performed to evaluate differences between the various types of COCs (e.g. estrogen dose, type of progestin) and the assays used to assess total T or free T.

RESULTS

A total of 151 records were identified by systematic review and 42 studies with a total of 1495 healthy young women (age range: 18-40 years) were included in the meta-analysis. All included studies were experimental studies and 21 were non-comparative. Pooling of the results derived from all the included papers showed that total T levels significantly decreased during COC use [mean difference (MD) (95% confidence interval, CI) -0.49 nmol/l (-0.55, -0.42); P < 0.001]. Significantly lower levels of free T were also found [relative change (95% CI) 0.39 (0.35, 0.43); P < 0.001], with a mean decrease of 61%. On the contrary, SHBG concentrations significantly increased during all types of COC use [MD (95% CI) 99.08 nmol/l (86.43, 111.73); P < 0.001]. Subgroup analyses revealed that COCs containing 20-25 µg EE had similar effects on total and free T compared with COCs with 30-35 µg EE. In addition, suppressive effects on T levels were not different when comparing different types of progestins. However, subgroup analyses for the estrogen dose and the progestin type in relation to changes in SHBG levels did show significant differences: COCs containing second generation progestins and/or the lower estrogen doses (20-25 µg EE) were found to have less impact on SHBG concentrations.

CONCLUSIONS

The current literature review and meta-analysis demonstrates that COCs decrease circulating levels of total T and free T and increase SBHG concentrations. Due to the SHBG increase, free T levels decrease twice as much as total T. The estrogen dose and progestin type of the COC do not influence the decline of total and free T, but both affect SHBG. The clinical implications of suppressed androgen levels during COC use remain to be elucidated.

Effect of raltegravir on estradiol and norgestimate plasma pharmacokinetics following oral contraceptive administration in healthy women

AIMS

Oral contraceptives such as norgestimate-ethinyl estradiol (Ortho Tri-Cyclen®) are commonly prescribed in the HIV-infected patient population. A placebo-controlled, randomized, two-period crossover study in healthy HIV-seronegative subjects was conducted to assess the effect of raltegravir on the pharmacokinetics of the estrogen and progestin components of norgestimate-ethinyl estradiol [ethinyl estradiol (EE) and norelgestromin (NGMN), an active metabolite of norgestimate (NGT)].

METHODS

In each of two periods, nineteen healthy women established on norgestimate-ethinyl estradiol contraception (21 days of active contraception; 7 days of placebo) received either 400 mg raltegravir or matching placebo twice daily on days 1-21. Pharmacokinetics were analysed on day 21 of each period.

RESULTS

The geometric mean ratio (GMR) and 90% confidence interval (CI) for the EE component of norgestimate-ethinyl estradiol when co-administrated with raltegravir relative to EE alone was 0.98 (0.93-1.04) for the area under the concentration-time curve from 0 to 24 h (AUC(0-24 h) ) and 1.06 (0.98-1.14) for the maximum concentration of drug in the plasma (C(max) ); the GMR (90% CI) for the NGMN component of norgestimate-ethinyl estradiol when co-administered with raltegravir relative to NGMN alone was 1.14 (1.08-1.21) for AUC(0-24 h) and 1.29 (1.23-1.37) for C(max) . There were no discontinuations due to a study drug-related adverse experience, nor any serious clinical or laboratory adverse experience.

CONCLUSIONS

Raltegravir has no clinically important effect on EE or NGMN pharmacokinetics. Co-administration of raltegravir and an oral contraceptive containing EE and NGT was generally well tolerated; no dose adjustment is required for oral contraceptives containing EE and NGT when co-administered with raltegravir.

The effects of oral contraceptives on androgen levels and their relevance to premenstrual mood and sexual interest: a comparison of two triphasic formulations containing norgestimate and either 35 or 25 μg of ethinyl estradiol

PURPOSE

This study compared two oral contraceptives (OCs) with the same triphasic regimen of progestin (norgestimate 0.18, 0.215 and 0.25 mg) but differing doses of ethinyl estradiol (EE) - 25 and 35 microg EE - in their effects on androgens, mood and sexual interest in women starting on OCs.

METHODS

Total testosterone (T), free testosterone (FT), sex-hormone-binding globulin (SHBG) and dehydroepiandrosterone sulphate (DHEA-S), together with measures of mood [Beck Depression Inventory (BDI)], sexual interest [Dyadic and Solitary subscales of the Sexual Desire Inventory (SDI)] and self-reported side effects were assessed before starting on the OC and again after 3 months of use.

RESULTS

Sixty women, all university students, were randomized to receive either the 25 microg EE (N/EE25) or the 35 microg EE (N/EE35) pill; 12 women discontinued, leaving 48 who completed the 3-month study. Their mean age was 19.7 years (18-30) and they were predominantly white and single. Both OCs produced reductions in mean T [N/EE35: from 1.33 to 0.60 nmol/L, p<.001; N/EE25: from 1.12 to 1.02 nmol/L; nonsignificant (NS)] and FT (N/EE35: from 41.3 to 4.4 pmol/L, p<.001; N/EE25: from 25.4 to 7.9 pmol/L, p<.01), but the reduction in both T and FT was significantly greater with the higher EE dose (N/EE35) (p=.05 and p=.03, respectively). DHEA-S was also reduced with both formulations (N/EE35: from 7.26 to 5.22 micromol/L); N/EE25: from 7.50 to 5.39 micromol/L), although the reduction was only significant in the N/EE35 group (p<.02). Considerable variability in changes in mood was evident with both OCs, with some women showing predominantly negative effects (10 in N/EE35, 5 in N/EE25); others, positive effects (9 in N/EE35, 17 in N/EE25) and some, no change (four in each group). Women using N/EE25 were significantly more likely to show improvement in premenstrual mood than those in the N/EE35 group (p<.02), although there was no correlation between changes in BDI and FT or DHEA-S. Sexual interest scores did not change significantly from baseline to posttreatment with either OC (N/EE35: dyadic, from 40.5 to 39.6, NS; solitary, from 5.9 to 6.4, NS; N/EE25: dyadic, from 36.7 to 37.0, NS; solitary, from 5.0 to 4.2, NS).

CONCLUSION

The lower EE pill reduced FT less and was associated with greater improvement in premenstrual mood. A causal relation between these two effects is uncertain.

Does oral contraceptive-induced reduction in free testosterone adversely affect the sexuality or mood of women?

The aim of this study was to examine whether changes in plasma androgen levels (total testosterone (T), free testosterone (FT), and dehydro-epiandrosterone-sulfate (DHEA-S)) induced by oral contraceptive (OC) use were related to changes in sexual interest or response or in mood. Sixty-one women provided blood samples and were assessed, using interviews and standardized questionnaires, prior to starting, and after 3 months on OCs (Ortho-Tricyclen, Ortho-Tricyclen-Lo, or Ortho-Cyclen, all containing the same progestagen, norgestimate). Significant decreases in T, FT, and DHEA-S were found after 3 months, although the extent of reduction was variable across women. There was some support for a relationship between the degree of reduction in total T and FT and the frequency of sexual thoughts after 3 months on OCs. However, some women had no loss of sexual interest in spite of substantial reduction in FT, and there was overall no evidence that reduction in FT affected enjoyment of sexual activity with a partner. The findings are consistent with the idea that some women may be more sensitive to changes in T than others. No relationship was found between negative mood, as assessed by the Beck Depression Inventory, and changes in T, FT, or DHEA-S.

Antiandrogenic activity of norgestimate in a human androgen-dependent stable-transfected cell line

BACKGROUND

Acne occurs from an overstimulation of the sebaceous glands by high levels of androgens or because sebaceous glands are hypersensitive to normal levels of testosterone. In women with moderate acne, norgestimate (NG) in association with ethinyl estradiol (EE) is acknowledged as an effective treatment; this is related to the effect of oral contraceptives on androgen production and transport. However, the antiandrogenic properties of NG itself have been poorly studied.

DESIGN

The present work was undertaken to find out whether NG and its derivative, 17-deacetylnorgestimate (dNG), present antiandrogen activity. First, we studied the effect of NG and dNG on the intracellular localization of green fluorescent protein (GFP)-labeled androgen receptor (AR). Then, we compared the AR activity of NG and dNG with that of cyproterone acetate (CPA), a gold-standard antiandrogenic compound, by investigating competitive binding, antagonist activity and transactivation level of AR.

RESULTS

NG and dNG decreased GFP-AR nuclear translocation, revealing their antiandrogenic property, as for CPA. In the whole cell competition assay performed in a human cell line stably expressing an AR-responsive luminescent reporter gene (PALM cells) with (3)H-labeled R1881 as tracer, NG and dNG were slightly stronger competitors than the antiandrogen CPA. Half-maximal inhibition (K(i)) of (3)H-labeled R1881 (10(-9) M) binding occurred at 4.2 +/- 0.5 x 10(-8) M of NG, 3.4 +/- 0.4 x 10(-8) M of dNG and 6.6 +/- 0.8 x 10(-8) M of CPA. Comparison of antagonist activities of NG, dNG and CPA on AR transactivation levels showed that NG, dNG and CPA inhibited androgen-induced luciferase activity in PALM cells. We observed slight and similar inhibition with 6 x 10(-8) M respectively of NG, dNG and CPA. For the three compounds, the best inhibitory effect was found at 3 x 10(-7) M: 24% for NG and dNG vs. 47% for CPA. The antiandrogenic activity of NG and dNG was found to be 50% that of CPA.

CONCLUSION

In a human androgen-dependent stable-transfected cell line, a useful tool for studying AR transcriptional activity and its subnuclear localization in the presence of androgens and antiandrogens, we demonstrated that NG and dNG have antiandrogenic properties that could partly explain the efficacy of NG in association with EE for the treatment of moderate acne in women.

Pharmacology of estrogens and progestogens: influence of different routes of administration

This review comprises the pharmacokinetics and pharmacodynamics of natural and synthetic estrogens and progestogens used in contraception and therapy, with special consideration of hormone replacement therapy. The paper describes the mechanisms of action, the relation between structure and hormonal activity, differences in hormonal pattern and potency, peculiarities in the properties of certain steroids, tissue-specific effects, and the metabolism of the available estrogens and progestogens. The influence of the route of administration on pharmacokinetics, hormonal activity and metabolism is presented, and the effects of oral and transdermal treatment with estrogens on tissues, clinical and serum parameters are compared. The effects of oral, transdermal (patch and gel), intranasal, sublingual, buccal, vaginal, subcutaneous and intramuscular administration of estrogens, as well as of oral, vaginal, transdermal, intranasal, buccal, intramuscular and intrauterine application of progestogens are discussed. The various types of progestogens, their receptor interaction, hormonal pattern and the hormonal activity of certain metabolites are described in detail. The structural formulae, serum concentrations, binding affinities to steroid receptors and serum binding globulins, and the relative potencies of the available estrogens and progestins are presented. Differences in the tissue-specific effects of the various compounds and regimens and their potential implications with the risks and benefits of hormone replacement therapy are discussed.