Comparative progestational and androgenic activity of norgestimate and levonorgestrel in the rat

Pharmacokinetics of Levonorgestrel in Rat and Minipig and Pharmacokinetics of Etonogestrel in Rat Following Various Administration Routes

1. The objective of these studies was to determine the pharmacokinetics of levonorgestrel and etonogestrel in Sprague-Dawley rat or Göttingen minipig following various administration routes.2. Four sequential crossover studies were conducted: Study 1 administered levonorgestrel 30 µg intravenously and intradermally in four minipigs; Study 2 administered levonorgestrel 30 µg intravenously in 12 rats; Study 3 administered levonorgestrel 60 µg intravenously and subcutaneously in 12 rats; and Study 4 administered etonogestrel 30 µg intravenously in 12 rats. Samples were quantified using liquid chromatography-tandem mass spectrometry and pharmacokinetic parameters were estimated via noncompartmental analysis.3. C_max and AUC_inf for etonogestrel and levonorgestrel were similar following 30 µg intravenous bolus in rat, suggesting comparable pharmacokinetics. Levonorgestrel exposure was dose-proportional in rats, based on two-fold higher AUC_inf following levonorgestrel 60 versus 30 µg. Bioavailability of intradermal and subcutaneous levonorgestrel was 97.7% (Study 1) and 90.3% (Study 3), respectively. The minipig levonorgestrel clearance was 21.5 L/hr, which was about 10-fold higher than both the rat levonorgestrel (range: 0.985 to 1.45 L/hr) and etonogestrel clearance (range: 0.803 to 0.968 L/hr).4. These studies contribute to the gap in knowledge of nonclinical levonorgestrel and etonogestrel pharmacokinetics, which is necessary for ongoing development of long-acting reversible contraceptives.

Combined Oral Contraceptives and Venous Thromboembolism: Review and Perspective to Mitigate the Risk

Many factors must be considered and discussed with women when initiating a contraceptive method and the risk of venous thromboembolism (VTE) is one of them. In this review, we discuss the numerous strategies that have been implemented to reduce the thrombotic risk associated with combined oral contraceptives (COCs) from their arrival on the market until today. Evidences suggesting that COCs were associated with an increased risk of VTE appeared rapidly after their marketing. Identified as the main contributor of this risk, the dosage of the estrogen, i.e., ethinylestradiol (EE), was significantly reduced. New progestins were also synthetized (e.g., desogestrel or gestodene) but their weak androgenic activity did not permit to counterbalance the effect of EE as did the initial progestins such as levonorgestrel. Numerous studies assessed the impact of estroprogestative combinations on hemostasis and demonstrated that women under COC suffered from resistance towards activated protein C (APC). Subsequently, the European Medicines Agency updated its guidelines on clinical investigation of steroid contraceptives in which they recommended to assess this biological marker. In 2009, estradiol-containing COCs were marketed and the use of this natural form of estrogen was found to exert a weaker effect on the synthesis of hepatic proteins compared to EE. In this year 2021, a novel COC based on a native estrogen, i.e., estetrol, will be introduced on the market. Associated with drospirenone, this preparation demonstrated minor effects on coagulation proteins as compared with other drospirenone-containing COCs. At the present time, the standard of care when starting a contraception, consists of identifying the presence of hereditary thrombophilia solely on the basis of familial history of VTE. This strategy has however been reported as poorly predictive of hereditary thrombophilia. One rationale and affordable perspective which has already been considered in the past could be the implementation of a baseline screening of the prothrombotic state to provide health care professionals with objective data to support the prescription of the more appropriate contraceptive method. While this strategy was judged too expensive due to limited laboratory solutions, the endogenous thrombin potential-based APC resistance assay could now represent an interesting alternative.

New steroidal derivatives synthesized using 3beta-hydroxyandrosten-17-one as starting material

In this study, we synthesized some new substituted steroidal derivatives using 3beta-hydroxyandrosten-17-one (dehydroepiandrosterone) as starting material. The synthesized steroidal derivatives 1-11 were evaluated for their androgenic-anabolic activities compared to testosterone as positive control. Details of the synthesis, spectroscopic data and toxicity (LD50) of synthesized compounds are reported.

Postcoital treatment with levonorgestrel does not disrupt postfertilization events in the rat

Levonorgestrel (LNG), a progestin widely used for regular hormonal contraception, is also used for emergency contraception (EC) to prevent pregnancy after unprotected intercourse. However, its mode of action in EC is only partially understood. One unresolved question is whether or not EC prevents pregnancy by interfering with postfertilization events. Here, we report the effects of acute treatment with LNG upon ovulation, fertilization and implantation in the rat. LNG inhibited ovulation totally or partially, depending on the timing of treatment and/or total dose administered, whereas it had no effect on fertilization or implantation when it was administered shortly before or after mating, or before implantation. It is concluded that acute postcoital administration of LNG at doses several-fold higher than those used for EC in women, which are able to inhibit ovulation, had no postfertilization effect that impairs fertility in the rat.

Inhibition of skin 5 alpha-reductase by oral contraceptive progestins in vitro

Androgenic disorders of female skin such as hirsutism, acne and alopecia are etiologically caused by androgen excess. Skin 5 alpha-reductase activity is a major factor influencing the manifestation of endogenous androgen excess in women. Oral contraceptives have proven useful for the treatment of androgen disorders of the skin. The mechanisms of action by which oral contraceptives correct skin androgen levels may include inhibition of 5 alpha-reductase and androgen receptor activity. We investigated the inhibitory effect of oral contraceptive progestins and ethinyl estradiol on skin 5 alpha-reductase and their influence on androgen receptor activity and affinity, using three different in vitro assay systems. It was shown that norgestimate blocked 5 alpha-reductase activity with an IC50 value of 10 microM, followed by levonorgestrel (IC50 52 microM), dienogest (IC50 55 microM), cyproterone acetate (IC50 87 microM) and gestodene (IC50 98 microM). To determine the full androgenic potential of the progestins, androgen receptor binding affinities and activation potentials were determined. The progestins norgestimate and dienogest in particular combined 5 alpha-reductase inhibition with minimal androgenic potential. These data demonstrate that the progestins norgestimate and dienogest might help in the treatment of clinical hyperandrogeny in women.

The epidemiology of oral contraceptive use: a critical review of the studies on oral contraceptives and the health of young women

Recent observational studies show a slightly increased risk of venous thromboembolism among users of newer combined oral contraceptives with odds ratios between 0.8 and 2.3 when compared with users of older oral contraceptives. The controversy regarding the newer oral contraceptives is reviewed by analyzing the recent studies with epidemiologic methods. Key studies on venous thromboembolism may be subject to bias related to prescribing criteria, diagnostics, hospital referral, cohort effects, and residual confounding, resulting in an overestimate of the risk of venous thromboembolism associated with the newer oral contraceptives. The studies on stroke showed no difference between newer and older oral contraceptives, and studies on myocardial infarction show that newer oral contraceptives carry no risk of this event. Newer-generation oral contraceptives are unlikely to constitute a significant hazard to the user population with regard to venous thromboembolism. The results for other disease entities also need to be taken into account when the results on venous thromboembolism are assessed on a population basis.

The increased risk of venous thromboembolism and the use of third generation progestagens: role of bias in observational research. The Transnational Research Group on Oral Contraceptives and the Health of Young Women

A matched case-control study was undertaken in 10 centers in Germany and the United Kingdom to explore the association of current use of major combination oral contraceptives with the occurrence of venous thromboembolism. The cases recruited were 505 women aged 16-44 years with venous thromboembolism, controls were 1877 women (at least 3 controls per case) matched for 5-year age group and region without VTE. The main outcome measures were odds ratios derived by comparing current use of a specific oral contraceptive or group of OC against current use of other groups or against no current use of OC. The odds ratios (95% confidence intervals) for venous thromboembolism were: for third generation products (low dose ethinyloestradiol, gestodene and desogestrel) versus second generation products (low dose ethinyloestradiol, no gestodene and desogestrel, 1.5 (1.1 to 2.0), for third versus second generation products with norgestimate included in third generation, 1.6 (1.2 to 2.2). The odds ratios for current use for women aged 16-44 of specific progestagens versus levonorgestrel-containing compounds were 1.7 (1.1 to 2.6) for gestodene, 1.8 (1.2 to 2.6) for desogestrel, 1.9 (1.0 to 3.6) for norgestimate and 1.3 (0.7 to 2.5) for progestagen-only pills. For women aged 25 to 44 likely to be exposed to any of these progestagens, odds ratios for the comparison of progestagens versus levonorgestrel showed a successive increase by market introduction ranging from 1.5 (0.9 to 2.5) for desogestrel with 30 micrograms oestrogen content (introduced 1981) to 2.8 (1.3 to 6.5) for desogestrel with 20 micrograms oestrogen content (introduced 1992) significant in linear trend analysis (p = 0.00012). The influence of norgestimate classification as third or second generation product does not significantly alter the results regarding the association of third generation products and venous thromboembolism. A direct comparison of current use of norgestimate (which is primarily metabolized to levonorgestrel) versus levonorgestrel shows an increased odds ratio. The trend of increasing risk of progestagens by recency of market introduction when compared with levonorgestrel is strongly indicative of the existence of external bias due to attrition of susceptibles.

Comparative progestational activity of norgestimate, levonorgestrel-oxime and levonorgestrel in the rat and binding of these compounds to the progesterone receptor

The progestational activity of norgestimate (NORG), levonorgestrel-oxime (LNG-oxime) and levonorgestrel (LNG) were compared in a pregnancy maintenance study in rats. The compounds were administered subcutaneously to pregnant rats at several doses, blood samples were collected repeatedly, and the concentration of LNG was measured in these samples. It could be demonstrated that following the administration of NORG and LNG-oxime, LNG was a major metabolite present in the serum. The pharmacological response in rats treated with NORG and LNG-oxime could be related to the systemic exposure of these animals to metabolically derived LNG. Thus, both NORG and LNG-oxime can be regarded as pro-drugs of LNG, the latter being almost exclusively responsible for the pharmacological activity of both pro-drugs. This notion was further supported by studies on the comparative binding affinity of these compounds to rabbit and human progesterone receptor (PR). LNG exhibited the highest binding affinity of the compounds studied. Relative binding affinity (RBA) values of LNG using progesterone as reference (100%) were found to be 125% for rabbit PR (rPR), 143% for human uterine PR (hPR) and 125% for recombinant hPR, respectively. In contrast to LNG, NORG exhibited only a low affinity to the PR, which is documented by RBA values of 1.2% for rPR, 3.2% for uterine hPR and 9% for recombinant hPR. The corresponding values of LNG-oxime were 30% (rPR), 20% (uterine hPR) and 18% (recombinant hPR), respectively. Thus, the combined experimental evidence of the present study does not support the view of NORG being a progestogen on its own as has been suggested by others.