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

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.

Acetylene in Organic Synthesis: Recent Progress and New Uses

Recent progress in the leading synthetic applications of acetylene is discussed from the prospect of rapid development and novel opportunities. A diversity of reactions involving the acetylene molecule to carry out vinylation processes, cross-coupling reactions, synthesis of substituted alkynes, preparation of heterocycles and the construction of a number of functionalized molecules with different levels of molecular complexity were recently studied. Of particular importance is the utilization of acetylene in the synthesis of pharmaceutical substances and drugs. The increasing interest in acetylene and its involvement in organic transformations highlights a fascinating renaissance of this simplest alkyne molecule.

Levonorgestrel decreases cilia beat frequency of human fallopian tubes and rat oviducts without changing morphological structure

Levonorgestrel, a derivative of progesterone, effectively protects women against unwanted pregnancy as an emergency contraceptive. Previous studies have not been successful in determining the mechanism by which levonorgestrel acts. In the present study we analysed cilia beat action and cilia morphology following levonorgestrel exposure in vitro and in vivo using both light and electron microscopy. There was a significant decrease in the ciliary beat frequency (CBF) of human fallopian tubes between mucosal explants bathed in 5 μmol/L levonorgestrel and those bathed in medium alone (P < 0.05). There was a tendency for CBF to decrease more in the ampulla than in isthmus, but there were no differences between the proliferative and secretory phases. In rat oviducts, levonorgestrel produced a similar reduction in CBF (~ 10%) compared with the saline control group (P < 0.05). Histological and ultrastructural analysis demonstrated no changes in the percentage of ciliated cells or in the classic '9 + 2' structure of cilia following levonorgestrel treatment in either system. Thus, levonorgestrel reduces CBF without damaging cilia morphology. Decreases in CBF may indicate a pathological role for levonorgestrel in the transportation of the ovum and zygote in the fallopian tube.

The challenge presented by progestins in ecotoxicological research: a critical review

Around 20 progestins (also called gestagens, progestogens, or progestagens) are used today in assisting a range of medical conditions from endometrial cancer to uterine bleeding and as an important component of oral contraception. These progestins can bind to a wide range of receptors including progestin, estrogen, androgen, glucocorticoid, and mineralocorticoid receptor, as well as sex hormone and corticosteroid binding globulins. It appears that only five of these (four synthetic and one natural) progestins have so far been studied in sewage effluent and surface waters. Analysis has reported values as either nondetects or low nanograms per liter in rivers. Seven of the progestins have been examined for their effects on aquatic vertebrates (fish and frogs). The greatest concern is associated with levonorgestrel, norethisterone, and gestodene and their ability to reduce egg production in fish at levels of 0.8-1.0 ng/L. The lack of environmental measurements, and some of the contradictions in existing values, however, hampers our ability to make a risk assessment. Only a few nanograms per liter of ethynodiol diacetate and desogestrel in water would be needed for fish to receive a human therapeutic dose for these progestins according to modeled bioconcentration factors. But for the other synthetic progestins levels would need to reach tens or hundreds of nanograms per liter to achieve a therapeutic dose. Nevertheless, the wide range of compounds, diverse receptor targets, and the effect on fish reproduction at sub-nanogram-per-liter levels should prompt further research. The ability to impair female reproduction at very low concentrations makes the progestins arguably the most important pharmaceutical group of concern after ethinylestradiol.

Differential effects of synthetic progestagens on neuron survival and estrogen neuroprotection in cultured neurons

Progesterone and other progestagens are used in combination with estrogens for clinical purposes, including contraception and postmenopausal hormone therapy. Progesterone and estrogens have interactive effects in brain, however interactions between synthetic progestagens and 17β-estradiol (E2) in neurons are not well understood. In this study, we investigated the effects of seven clinically relevant progestagens on estrogen receptor (ER) mRNA expression, E2-induced neuroprotection, and E2-induced BDNF mRNA expression. We found that medroxyprogesterone acetate decreased both ERα and ERβ expression and blocked E2-mediated neuroprotection and BDNF expression. Conversely, levonorgestrel and nesterone increased ERα and or ERβ expression, were neuroprotective, and failed to attenuate E2-mediated increases in neuron survival and BDNF expression. Other progestagens tested, including norethindrone, norethindrone acetate, norethynodrel, and norgestimate, had variable effects on the measured endpoints. Our results demonstrate a range of qualitatively different actions of progestagens in cultured neurons, suggesting significant variability in the neural effects of clinically utilized progestagens.

Challenges in the gynecologic care of premenopausal women with breast cancer

Premenopausal women with a new diagnosis of breast cancer are faced with many challenges. Providing health care for issues such as gynecologic comorbidities, reproductive health concerns, and vasomotor symptom control can be complicated because of the risks of hormone treatments and the adverse effects of adjuvant therapies. It is paramount that health care professionals understand and be knowledgeable about hormonal and nonhormonal treatments and their pharmacological parameters so they can offer appropriate care to women who have breast cancer, with the goal of improving quality of life. Articles for this review were identified by searching the PubMed database with no date limitations. The following search terms were used: abnormal uterine bleeding, physiologic sex steroids, endometrial ablation, hysteroscopic sterilization, fertility preservation in endometrial cancer, tranexamic acid and breast cancer, menorrhagia treatment and breast cancer, abnormal uterine bleeding and premenopausal breast cancer, levonorgestrel IUD and breast cancer, tamoxifen and gynecologic abnormalities, tamoxifen metabolism, hormones and breast cancer risk, contraception and breast cancer, pregnancy and breast cancer, and breast cancer and infertility treatment.

3- and 19-oximes of 16alpha,17alpha-cyclohexanoprogesterone derivatives: synthesis and interactions with progesterone receptor and other proteins

Series of 3- and 19-oximes of 16alpha,17alpha-cyclohexanoprogesterone derivatives (pregna-d'-pentaranes) have been synthesized with the aim of probing the surfaces of progesterone receptor's and two other protein ligand binding pockets neighboring to 3- and 19-positions of steroid core. The same derivatives were also studied as possible intermediates for attachment to matrixes. The data on affinity constants suggest the presence of hydrophobic cavities with hydrophilic necks in the progesterone receptor and serum pentaranophylin near C19 of bound ligand and the lack of such a cavity in uterine pentaranophylin. Any of 3-oxime substitutions were found to significantly diminish the ligand affinity for the progesterone receptor. It was also found that some of these modifications, in the Z-configuration particularly, might increase the affinity for serum and uterine pentaranophylins. The latter finding suggests the presence of large cavities near C3 of bound ligand in these proteins and interchangeability between 3-keto and 3-oxime groups in ligand-protein interactions.

Effect of intermittent treatment with mifepristone on bleeding patterns in Norplant® implant users

A double-blind, placebo-controlled, randomized trial, was carried out in 120 Norplant users to evaluate the effect of mifepristone, 100 mg/day administered for 2 consecutive days every 30 days, on the vaginal bleeding pattern. Treatment was given from months 2-7 of implant use. Volunteers recorded bleeding and spotting days, during treatment and for the ensuing 6-month period. During treatment, women on mifepristone recorded the same frequency of bleeding/spotting episodes but significantly less prolonged bleeding episodes than placebo controls (mean +/- SD: 11 +/- 3 vs. 22 +/- 23 days) and their total number of bleeding days was 35% lower than in the placebo group. After the end of mifepristone use, bleeding patterns were similar in both groups. One pregnancy occurred in the mifepristone-treated group, in month 6 of treatment, the outcome was a healthy male baby. We conclude that intermittent administration of mifepristone can offer a clinically significant improvement of the vaginal bleeding pattern in Norplant users.

An overview of nomegestrol acetate selective receptor binding and lack of estrogenic action on hormone-dependent cancer cells

The specific pharmacological profile of the 19-norprogestin nomegestrol acetate (NOMAC) is, at least in part, defined by its pattern of binding affinities to the different steroid hormone receptors. In the present study, its affinity to the progesterone receptor (PgR), the androgen receptor (AR) and the estrogen receptor (ER) was re-evaluated and compared to those obtained for progesterone (P) and several progestins. The characteristics of binding to the PgR in rat uterus were determined and Ki were found to be roughly similar with 22.8 and 34.3 nM for NOMAC and P, respectively. The binding characteristics of 3H-NOMAC were also determined and compared to that of 3H-ORG2058 with Kd of 5 and 0.6 nM, respectively for rat uterus and 4 and 3 nM, respectively for human T47-D cells. Structure-affinity and -activity relationships were studied on a variety of compounds related to NOMAC in order to assess its specificity as a progestin. The effects of NOMAC on the binding of androgen to the AR were investigated, using rat ventral prostate as target model. Contrary to what was observed for MPA, the RBA of NOMAC was found to decline with time, showing anti-androgenic rather than androgenic potential, a result that was confirmed in vivo. Regarding the ER, since none of the progestins were able to compete with estrogen for binding in rat uterus as well as in Ishikawa cells, the induction of alkaline phosphatase activity (APase) was used as an estrogen-specific response. It confirmed the intrinsic estrogenicity of progestins derived from 19-nor-testosterone (19NT), norethisterone acetate (NETA), levonorgestrel (LNG) or norgestimate (NGM) and others. In contrast, all P and 19-norP derivatives remained inactive. Finally, to complete this overview of NOMAC at the sex steroid receptor levels, the lack of estrogenic or estrogenic-like activity was checked out in different in vitro models. Data from this study have demonstrated that NOMAC is a progestin that has greater steroid receptor selectivity compared to MPA or some other synthetic progestins. It may provide a better pharmacological profile than those progestins currently in use in HRT and OC.

Reporter cell lines are useful tools for monitoring biological activity of nuclear receptor ligands

To characterize the specificity of synthetic compounds for nuclear receptors, we established stable cell lines expressing the luciferase gene and different wild-type or chimaeric receptors. MCF-7 cells, which express the oestrogen receptor alpha (ER alpha), and HeLa cells, which do not express the oestrogen receptor, were transfected with a plasmid containing the luciferase gene downstream from a minimum promoter (beta-globin) and an oestrogen-responsive element, generating the MELN and the HELN cell lines, respectively. MELN cells enabled the detection of compounds that bind to the ER alpha or interfere with its pathway. HELN cells were used to establish stable transfectants expressing different nuclear receptors containing the DNA-binding domain of the oestrogen receptors. We thus established ER alpha or ER beta reporter cell lines by transfecting ER alpha or ER beta expression plasmids, and also retinoic acid receptor alpha, beta or gamma reporter cell lines by transfecting the chimaeric RAR gene, in which the DNA-binding domain was replaced by the ER alpha DNA-binding domain.

The effects of monophasic and triphasic oral contraceptives on ovarian function and endometrial thickness

OBJECTIVE

To analyze and compare the effects of seven low-dose oral contraceptives (OCs) on ovarian function and endometrial thickness.

METHODS

Cross-sectional study of users of one of five monophasic OCs, one of two triphasic OCs and a control group of non-users. Ovarian function, endometrial thickness and serum hormone levels were monitored during days 10-12 and 16-18 of the cycle.

RESULTS

Serum estradiol was suppressed in OC users to a greater degree during days 16-18 than during days 10-12, whereas serum progesterone during 16-18 was in the anovulatory range with each preparation. Ovarian activity as measured by follicular size was lowest with desogestrel-containing OCs, whereas greater activity was seen with triphasic levonorgestrel/ethinylestradiol and triphasic norgestimate/ethinylestradiol. Endometrial thickness in OC users was significantly smaller than in controls.

CONCLUSIONS

All preparations demonstrated profound suppression of ovarian activity and effectively prevented ovulation. Ovarian suppression with desogestrel/ethinylestradiol 150/20 did not differ from that of other OCs despite its lower ethinylestradiol content. The use of both triphasic OCs, having a relatively low progestogenic activity, was associated with a higher ovarian activity than that of the monophasic OCs.