Norgestrel Research Articles

The long-term effects of norgestrel on the reproductive and thyroid systems in adult zebrafish at environmentally relevant concentrations

Progestins are crucial steroid hormones that have attracted wide attention due to their endocrine disrupting effects in fish. The aim of this study is to investigate the effects of long-term exposure to low concentrations of norgestrel (NGT) on the reproductive and thyroid endocrine systems of adult zebrafish. Adult zebrafish were exposed to 7 and 39 ng/L NGT for a duration of 90 days. The results revealed that exposure to 39 ng/L NGT led to a significant up-regulation of 3β-hydroxysteroid dehydrogenase (hsd3b) and 20β-hydroxysteroid dehydrogenase (hsd20b) genes in the ovary of female zebrafish. Additionally, there was a significant up-regulation of 11β-hydroxysteroid dehydrogenase 2 (hsd11b2) gene in the testis of male zebrafish. Furthermore, egg production decreased significantly, accompanied by notable alterations in the proportion of ovarian development stages, as well as reductions of sex hormone levels (E2, 11-KT, and T) in both females and males. However, long-term exposure to low concentrations of NGT did not lead to changes in thyroid hormone levels and thyroid histopathology in adult zebrafish. The overall results imply that environmental concentrations of NGT have a strong endocrine disrupting effect on the reproductive system of zebrafish, while the thyroid system is not sensitive to NGT exposure. The present study underscores the reproductive endocrine impacts of NGT and emphasizes the necessity for prolonged exposure at environmental concentrations.

Norgestrel causes oxidative damage to the digestive gland of the clam Mactra veneriformis

Increasingly, progestins are being detected in aquatic environments, especially in aquaculture areas, and concern about their adverse effects on aquatic organisms is growing. However, the mechanisms underlying progestin-induced oxidative stress and the antioxidant response of aquatic invertebrates to progestin exposure are unknown. Researchers recently reported that norgestrel (NGT) likely causes oxidative stress in the clam Mactra veneriformis. In this study, we assessed reactive oxygen species (ROS) levels, antioxidant enzyme activity, malonaldehyde content, ultrastructure, and DNA damage in the digestive gland of M. veneriformis exposed to 7.69 or 756.62 ng/L of NGT for 21 days. We also conducted tandem mass tag-based quantitative proteomic analysis to detect the protein response and gain insights into response mechanisms in clams exposed to NGT. We found that NGT enhanced oxidative phosphorylation via the wingless/integrated signaling pathway and triggered ROS generation. The alterations of antioxidant enzyme activities suggested that these enzymes are involved in scavenging NGT-induced ROS. NGT weakened antioxidant defense by suppressing the antioxidant synthesis-related AMP-activated protein kinase/forkhead box O and sirtuin 1/forkhead box O pathways. Additionally, cell membrane dissolution, mitochondrial cristae rupture, DNA damage, elevation of malonaldehyde content, and oxidation of lipid, protein, and glucose occurred due to compromised redox homeostasis. Our results highlight the oxidative stress, antioxidant response, and oxidative damage induced by NGT in M. veneriformis and shed light on ecological risks of progestins to aquatic invertebrates.

In vitro exposure to environmentally relevant concentrations of norgestrel affects sperm physiology and reproductive success of the Pacific oyster Crassostrea gigas

Progestins in aquatic environments are of increasing concern, as shown by the results of toxicological studies on adult invertebrates with external fertilization. However, their potential effects on the gametes and reproductive success of such animals remain largely unknown. Thus, the current study assessed the effect of in vitro exposure of environmentally relevant concentrations (10 ng/L and 1000 ng/L) of norgestrel (NGT) on the sperm of Pacific oyster Crassostrea gigas, analyzing sperm motility, ultrastructure, mitochondrial function, ATP status, characteristic enzyme activities, and DNA integrity underlying fertilization and hatching success. The results showed that NGT increased the percentage of motile sperm by elevating intracellular Ca2+ levels, Ca2+-ATPase activity, creatine kinase activity, and ATP content. Although superoxide dismutase activity was enhanced to eliminate reactive oxygen species generated by NGT, oxidative stress occurred, as indicated by the increase in malonaldehyde content and damage to plasma membranes and DNA. As a consequence, fertilization rates decreased. However, hatching rates did not alter significantly, possibly as a result of DNA repair processes. This study demonstrates oyster sperm as a useful, sensitive tool for toxicological research of progestins and provides ecologically relevant information on reproductive disturbance in oysters resulting from exposure to NGT.

Fate of progesterone and norgestrel in anaerobic/anoxic/oxic (A/A/O) process: Insights from biotransformation and mass flow

Progesterone (P4) and norgestrel (NGT) are two steroid progestogens that can pose adverse effects on aquatic organisms at ng/L levels. Despite increasing concern on their occurrence and removal in wastewater, their fate in the wastewater treatment process has not been well documented. This study identified the transformation products (TPs) of P4 and NGT in anaerobic/anoxic/oxic (A/A/O) process. Potential functional genes involved in biotransformation of P4 and NGT were explored. The elimination or formation behavior of P4, NGT and convinced TPs along various units of A/A/O process was revealed through the mass flow. Results showed that 12 and 13 TPs were identified in the P4 and NGT groups respectively, wherein 10 identical TPs and C-19 structures transformation pathways were observed in both groups. Six genes were found that may be involved in dehydrogenation and isomerization reactions in the pathways. Mass flow indicated that P4 and NGT were mainly eliminated in anaerobic and anoxic units, while convinced TPs mainly formed in anaerobic and anoxic units and were then eliminated in aerobic unit. Further, the ecological risks of the effluent should not be ignored as residual compounds including P4 or NGT and their TPs in the effluent still posed adverse effects on zebrafish transcript levels.

Insight into the effect of wastewater-derived dissolved organic matter composition on norgestrel degradation in activated sludge: Coupled bacterial community and molecular characteristics

Dissolved organic matter (DOM) mediates the microbial transformation of micropollutants, including norgestrel (NGT) in natural waters. However, little is known of the effect of complex and variable wastewater-derived DOM composition on NGT degradation during wastewater treatment. In this study, the relationship between the compositions of initial DOM and NGT removal efficiencies of 17 wastewater treatment plants (WWTPs) in spring and summer were analyzed. The different molecular composition of DOM was selected in the lab to further explore its effect on NGT degradation by activated sludge. Results indicated that the DOM composition was a substantial driver of NGT removal in WWTPs. The discrepancies in the initial DOM composition contributed to the differences in the kinetics of NGT degradation by activated sludge. The larger rapid decay phase rates of NGT are usually accompanied by a large proportion of labile substances in DOM. High-throughput sequencing and ultrahigh-resolution mass spectrometry were used to further analyze the evolution of bacterial communities and DOM molecular composition were combined with network analysis to reveal the intrinsic relationship that how DOM composition affected NGT degradation by regulating core microbes. Eighty-nine core OTUs were significantly associated with NGT degradation, and 73 occurred in the rapid decay phase, implying that NGT degradation was mainly regulated by the initial composition of DOM. Nine major transformation products were identified in different groups with widely varying concentrations or relative abundances of these transformation products. This work provides valuable insights into the effects of wastewater-derived DOM composition on NGT degradation by activated sludge and innovatively explores the influence mechanisms from the bacterial community and molecular characterization perspectives.

Molecular insights into how SHBG dimerization exerts changes on ligand molecular recognition

Sex hormone binding globulin (SHBG) is a homodimeric glycoprotein and is the major carrier protein for sex steroids in plasma, regulating sex hormone availability in most vertebrate groups. Although it was initially thought that human dimeric SHBG bound a single ligand at the homodimer interface, studies demonstrated that dimeric SHBG binds a ligand to each subunit with similar affinity. In fact, the findings from recent experimental studies suggest that ligand binding to the SHBG dimer involves a complex allosteric mechanism involving conformational changes that limit observations of the presence of allosteric regulation. Therefore, we combined structural data with molecular dynamics simulations using Molecular Mechanics Generalized-Born Surface Area (MMGBSA) to dissect the structural and energetic basis for molecular recognition between five ligands whose affinities and binding positions on SHBG are known, i.e., 3β,17α-diol; 3β,17β-diol; DHT; norgestrel (NOG); and estradiol (E2), and monomeric and dimeric SHBG. Protein-ligand complexes, involving dimeric SHBG saturated with two ligands on each subunit, reproduce the experimental affinity tendency and allow the observation that dimerization exerts disparate effects on binding affinity, characteristic of negative cooperativity for E2, DHT, and NOG, whereas 3β-17α-diol and 3β-17β-diol lack allostery.

Transcriptomic and physiological changes in western mosquitofish (Gambusia affinis) after exposure to norgestrel

Norgestrel (NGT) is a synthetic progestin used in human and veterinary medicine. Adult female mosquitofish were exposed to NGT for 42 d at 377 ng L−1. The fin morphology and the liver transcriptome were assessed. NGT exposure increased ray 4:6 length ratio. As compared to the control, NGT treatment affected the expression of 11,772 annotated transcripts in female mosquitofish. Specifically, we found 5780 were repressed while 5992 were significantly induced. Gene ontology (GO) analysis showed that 53 KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways and 158 GO terms were significantly over expressed. Genes showing the largest magnitude of expression changes were related to fin development, androgen biosynthesis, and lipid and fatty acid metabolisms, suggesting the involvement of these biological processes in response to NGT exposure in G. affinis. This first comprehensive study on the transcriptomic alterations by NGT in G. affinis not only provides valuable information on the development of molecular markers but also opens new avenues for studies on the molecular mechanisms of effects of NGT in particular and possibly other progestins in G. affinis.

GENOTOXIC AND CARCINOGENIC STUDIES OF NORGESTREL IN DROSOPHILA MELANOGASTER

Objective: The aim of this study was to investigate, for the first time, the possible in vivo genotoxic and carcinogenic activity associated with exposure to norgestrel (NGT) drug through employing the very recently established and adjusted genotoxic and tumorigenic methods in Drosophila melanogaster.Methods: Two in vivo genotoxic test systems were used; one detects the somatic mutation and recombination effects (somatic mutation and recombination test [SMART] wing-spot test) and the other detects the primary DNA damage (the comet test) in the body cells of D. melanogaster. On the other hand, the warts (wts)-based SMART assay is a vital genetic examination in Drosophila used to identify and characterize cancer potential of compounds.Results: Four experimental doses of NGT were used (ranging from 0.24 μM to 16 μM). NGT was found to be non-genotoxic at all tested concentrations even at the highest dose level 16 μM and failed to increase the frequency of tumors in the somatic cells of D. melanogaster.Conclusion: Our results strengthen the hypothesis that steroidal drugs might act through a non-genotoxic carcinogen mechanism where the carcinogenic properties occur by direct stimulation of cellular proliferation through a steroid receptor-mediated mechanism. In addition, the results obtained in this research work may contribute to highlighting the importance of NGT as a potent neuroprotective antioxidant drug.

Alterations of secondary sex characteristics, reproductive histology and behaviors by norgestrel in the western mosquitofish (Gambusia affinis)

Synthetic hormones in wastewater effluents released into the aquatic environments may interfere with the normal endocrine systems of fish in receiving streams. Norgestrel (NGT) is a synthetic progestin widely used in oral contraceptives and frequently detected in wastewater effluents. In this study, adult female mosquitofish (Gambusia affinis) were exposed to three environmentally relevant concentrations of norgestrel (NGT) (i.e., 3.6, 35.8, and 368.0 ng L−1) for 42 d, fin morphology, histology of the ovary, and reproductive behaviors were evaluated. The results showed that NGT at all three concentrations caused an increased frequency of atretic follicular cells in ovaries and impaired mating behaviors exhibited by males toward the NGT-exposed females. In mosquitofish exposed to NGT at 35.8 and 368 ng L−1, the anal fin of females had an increased length ratio of ray4/ray 6, an increased width of ray 3, and increased number of segments in ray 3. The histopathological analysis showed that exposure to NGT increased the incidence of spermatogenesis in ovaries. Mating behavior was impaired 58.4%, 65.7%, and 76.4% (P < 0.01 in all cases) when mosquitofish were exposed to NGT at 3.6, 35.6 and 368.0 ng L−1, respectively. The rapid masculinization, the increased frequency of atretic follicles, the incidence of spermatogenesis in the ovary of female fish, and the altered reproductive behaviors suggest that wild populations of mosquitofish could be similarly affected inhabiting in NGT contaminated environments.

Reproductive effects of synthetic progestin norgestrel in zebrafish (Danio rerio)

The aim of this study was to assess the adverse effects of synthetic progestin norgestrel (NGT) on the reproduction of zebrafish by measuring the egg production, histology and transcriptional expression profiles along the hypothalamic-pituitary-gonadal (HPG) axis in adult zebrafish. After a pre-exposure period of 7 days, adult zebrafish were exposed to 6, 29 and 69 ng L−1 NGT for 21 days. The results showed that exposure to 69 ng L−1 NGT led to a significant up-regulation of follicle stimulating hormone, beta polypeptide (fshb), luteinizing hormone, beta polypeptide (lhb), progesterone receptor (pgr), estrogen receptor 1 (esr1) and androgen receptor (ar) genes in the brains, as well as significant up-regulation of hydroxysteroid 20-beta dehydrogenase (hsd20b) and hydroxysteroid 11-beta dehydrogenase 2 (hsd11b2) genes and down-regulation of 11-beta-hydroxylase (cyp11b) gene in the ovaries of females. In the testes of males, an overall down-regulation of steroidogenic acute regulatory protein (star), cytochrome P450-mediated side-chain cleavage enzyme (cyp11a1), cyp11b, hsd20b, hydroxysteroid 17-beta dehydrogenase type 3 (hsd17b3), hsd11b2 and ar genes were observed following exposure to different treatments of NGT. These transcriptional alterations imply that NGT could exhibit the potent progestogenic and androgenic activities in zebrafish. Egg production as well as histology in the ovaries and testes was not affected by NGT. Taken together, the overall results demonstrated that NGT could significantly affect transcriptional expression levels of genes related to HPG axis in zebrafish, and whether that change translates to additional physiological effects is needed further research.

Transcriptional and histological alterations in gonad of adult zebrafish after exposure to the synthetic progestin norgestrel.

The aim of the present study was to investigate the effects of norgestrel (NGT) on gonadal development in adult zebrafish. Adult zebrafish were exposed to NGT for 14 d at 871 ng L-1 for microarray analysis, and a follow-up experiment was conducted to further study the targeted pathway in adult zebrafish after exposure to NGT at 6.7, 83, and 912 ng L-1 by quantitative polymerase chain reaction (qPCR) and histological analysis. The microarray analysis revealed that 11 545 transcripts were identified. Gene ontology analysis showed organ development, system development, multicellular organismal development, single-organism developmental process, and developmental process were significantly enriched. A Venn diagram displayed 434 target genes involved in organ development, and these genes were common in these 5 development-related processes. Kyoto Encyclopedia of Genes and Genomes analysis showed that the notch signaling pathway was the top toxicity pathway, and it was selected as the target pathway for further qPCR analysis. The qPCR analysis revealed significant and dose-dependent alterations of most target genes involved in the notch signaling pathway in the gonads, even at an environmentally relevant concentration of 6.7 ng L-1 . The transcriptional patterns were consistent with the notch signaling cascade. In addition, NGT significantly increased the frequency of mature sperm and decreased the frequency of immature sperm at all concentrations. Meanwhile, NGT treatment increased the percentage of mature vitellogenic oocytes and atretic follicles at 912 ng L-1 but decreased the percentage of immature vitellogenic oocytes. Thus, the present study demonstrated significant developmental toxicity in the gonad of adult zebrafish even at environmentally relevant NGT concentrations. Environ Toxicol Chem 2017;36:3267-3276. © 2017 SETAC.

Metabolite Identification, Reaction Phenotyping, and Retrospective Drug-Drug Interaction Predictions of 17-Deacetylnorgestimate, the Active Component of the Oral Contraceptive Norgestimate.

Ortho Tri-Cyclen, a two-drug cocktail comprised of ethinylestradiol and norgestimate (13-ethyl-17-acetoxy-18, 19-dinor-17α-pregn-4-en-20yn-3 oxime), is commonly prescribed to avert unwanted pregnancies in women of reproductive age. In vivo, norgestimate undergoes extensive and rapid deacetylation to produce 17-deacetylnorgestimate (NGMN), an active circulating metabolite that likely contributes significantly to norgestimate efficacy. Despite being of primary significance, the metabolism and reaction phenotyping of NGMN have not been previously reported. Hence, detailed biotransformation and reaction phenotyping studies of NGMN with recombinant cytochrome P450 (P450), recombinant uridine 5'-diphospho-glucuronosyltransferases, and human liver microsomes in the presence and absence of selective P450 inhibitors were conducted. It was found that CYP3A4 plays a key role in NGMN metabolism with a fraction metabolized (fm) of 0.57. CYP2B6 and to an even lesser extent CYP2C9 were also observed to catalyze NGMN metabolism. Using this CYP3A4 fm value, the predicted plasma concentration versus time area under the curve (AUC) change in NGMN using a basic/mechanistic static model was found to be within 1.3-fold of the reported NGMN AUC changes for four modulators of CYP3A4. In addition to NGMN, we have also elucidated the biotransformation of norgestrel (NG), a downstream norgestimate and NGMN metabolite, and found that CYP3A4 and UGT1A1 have a major contribution to the elimination of NG with a combined fm value of 1. The data presented in this paper will lead to better understanding and management of NGMN-based drug-drug interactions when norgestimate is coadministered with CYP3A4 modulators.

Transcriptional alterations induced by binary mixtures of ethinylestradiol and norgestrel during the early development of zebrafish (Danio rerio)

Synthetic estrogens and progestins are commonly used in human and veterinary medicine. After use, they reach aquatic environments via discharge of wastewaters from human and animals, thus posing potential risks to organisms. So far, very little is known about their combined effects in aquatic organisms. The aim of this study was to investigate the effects of binary mixtures of ethinylestradiol (EE2) and norgestrel (NGT) on embryonic zebrafish (Danio rerio) by measuring transcriptional alterations. Zebrafish embryos were exposed to EE2 and NGT alone or in combination at concentrations between 36 and 5513ngL−1 for 96h post-fertilization (hpf). The results showed that most of gene transcriptions of hypothalamic-pituitary-gonadal axis (e.g., Pgr, Mprα, Esr1, Esr2a, Vtg1, Ar, Cyp11b, Star, Gnrh3 and Fshb) and circadian rhythm signaling (e.g., Cry1a, Cry2a, Cry2b, Per3, Arntl1b, Arntl2, Clock1a, Cry3 and Cry4) displayed most pronounced alterations in the mixtures as compared to single EE2 and NGT exposures. This finding suggests exposure to the binary mixtures of EE2 and NGT produced significantly enhanced effects in fish as compared to single chemical exposures, and their coexistence could have significant environmental implications.

Long-term exposure to environmentally relevant concentrations of progesterone and norgestrel affects sex differentiation in zebrafish (Danio rerio)

The aim of this study was to investigate the effects of progestins on the sex differentiation of zebrafish by measuring the sex ratio and transcriptions of genes related to sex differentiation (Amh, Dmrt1, Figa, Sox9a and Sox9b genes) as well as sex hormone levels and transcriptional expression profiles along the hypothalamic–pituitary–gonadal (HPG) and hypothalamic–pituitary–adrenal (HPA) axes in juvenile zebrafish. Exposure of zebrafish to 4, 33, 63ngL−1 progesterone (P4) or 4, 34, 77ngL−1 norgestrel (NGT) started at 20 days post fertilization (dpf) and ended at 60 dpf. The results showed that exposure to P4 caused a significant increase in proportion of females as well as significant down-regulation of Amh gene and up-regulation of Figa at a concentration of 63ngL−1. However, the shift in the sex ratio toward males was observed following exposure to 34 and 77ngL−1 NGT, which came along with the significant induction of Dmrt1 gene and inhibition of Figa gene. The sex hormones in exposed fish were measured with estrone being detected only in the fish exposed to the highest P4 concentration; whereas estradiol and androstenedione were detected only in the fish of the control and lowest NGT concentration. Furthermore, the increase in females was associated with the significant up-regulation of several key genes controlling the synthesis of sex hormones (i.e., Cyp17, Cyp19a1a and Hsd3b) following exposure to 63ngL−1 P4 whereas the significant down-regulation of Cyp11a1, Cyp17, Cyp19a1a and Hsd3b genes was observed in the male-biased populations caused by 34 and 77ngL−1 NGT. The overall results imply that both P4 and NGT could significantly affect sex differentiation in zebrafish, and that changes may be reflected by altered sex hormone levels and transcriptional expression profiles of genes related to synthesis of sex hormones.

Progesterone and norgestrel alter transcriptional expression of genes along the hypothalamic–pituitary–thyroid axis in zebrafish embryos-larvae

The aim of this study was to investigate the effects of progestins on the hypothalamic–pituitary–thyroid (HPT) axis in the early stage of zebrafish. Zebrafish embryos were exposed to progesterone (P4) or norgestrel (NGT) at 5, 50 and 100ngL−1 for 144h post fertilization (hpf), and the transcriptional levels of target genes along the hypothalamic–pituitary–thyroid axis were determined daily. The results showed that P4 had only minor effects on the mRNA expression of thyroglobulin (Tg), iodothyronine deiodinase type Ι (Dio1) and thyroid hormone receptor β (Thrb) genes. Similarly, the effects of NGT on transcripts of thyrotropin-releasing hormone (Trh), Dio1, iodothyronine deiodinase type II (Dio2) and thyroid hormone receptor α (Thra) genes were generally low. In addition, NGT resulted in some alterations of Tg and Thrb transcripts at different time points. However, a strong induction of Nis mRNA by P4 and NGT was observed in zebrafish embryos-larvae. The overall results showed that besides Nis no effects on the hypothalamic–pituitary–thyroid (HPT) axis are observed following exposure to P4 and NGT, which imply that both P4 and NGT have potential effects on the thyroid endocrine system by inducing transcript of Nis gene during the early stage of zebrafish.

Synthetic Progestins Differentially Promote or Prevent 7,12-Dimethylbenz(a)anthracene–Induced Mammary Tumors in Sprague-Dawley Rats

Recent clinical trials show that combined oral dosing with estrogen and progestin increases the incidence of breast cancer in postmenopausal women. Similarly, in a rat model system of mammary carcinogenesis, the synthetic progestin medroxyprogesterone acetate (MPA) decreases latency and increases incidence of 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors. The goal of this study was to compare the effects of four clinically relevant progestins, MPA, norgestrel (N-EL), norethindrone (N-ONE), and megestrol acetate (MGA), on DMBA-induced mammary carcinogenesis in the rat. The experimental protocol involved implantation of 60-day release progestin pellets four weeks after rats were treated with DMBA. In contrast to the effect of MPA, N-ONE, and N-EL, but not MGA, blocked DMBA-dependent carcinogenesis and a dose-dependent effect on tumor growth was shown for N-EL; MGA did not alter tumor growth. Histopathologic studies showed extensive hyperplastic lesions in mammary tissue of progestin-treated animals. Furthermore, following treatment with N-EL or N-ONE, immunohistochemical staining for vascular endothelial growth factor in hyperplastic mammary tissue was lower than in animals treated with DMBA plus MPA or DMBA alone. Expression of vascular endothelial growth factor receptor-1, estrogen receptor alpha, and progesterone receptor was also lower in hyperplastic mammary tissue in N-EL-, N-ONE-, and MGA-treated animals. Interestingly, N-EL stimulated progression of existing mammary tumors in DMBA/MPA-treated rats, suggesting stage-specific effects of N-EL in this model. Because N-EL and N-ONE prevent tumor growth in the early stages of DMBA-induced mammary carcinogenesis in rats, these progestins may have potential as chemopreventive agents in women with no history of breast disease or family history of breast cancer.

Synthetic progestins induce growth and metastasis of BT-474 human breast cancer xenografts in nude mice

Previous studies have shown that sequential exposure to estrogen and progesterone or medroxyprogesterone acetate (MPA) stimulates vascularization and promotes the progression of BT-474 and T47-D human breast cancer cell xenografts in nude mice (Liang et al, Cancer Res 2007, 67:9929). In this follow-up study, the effects of progesterone, MPA, norgestrel (N-EL), and norethindrone (N-ONE) on BT-474 xenograft tumors were compared in the context of several different hormonal environments. N-EL and N-ONE were included in the study because synthetic progestins vary considerably in their biological effects and the effects of these two progestins on the growth of human tumor xenografts are not known. Estradiol-supplemented intact and ovariectomized immunodeficient mice were implanted with BT-474 cells. Progestin pellets were implanted simultaneously with estradiol pellets either 2 days before tumor cell injection (ie, combined) or 5 days after tumor cell injections (ie, sequentially). Progestins stimulated the growth of BT-474 xenograft tumors independent of exposure timing and protocol, MPA stimulated the growth of BT-474 xenograft tumors in ovariectomized mice, and progestins stimulated vascular endothelial growth factor elaboration and increased tumor vascularity. Progestins also increased lymph node metastasis of BT-474 cells. Therefore, progestins, including N-EL and N-ONE, induce the progression of breast cancer xenografts in nude mice and promote tumor metastasis. These observations suggest that women who ingest progestins for hormone therapy or oral contraception could be more at risk for developing breast cancer because of proliferation of existing latent tumor cells. Such risks should be considered in the clinical setting.

Interactions between progestins and estradiol on serum lipids in the rat.

In female rats the influence of progestins of the estrane type [norethisterone acetate (NEA), norgestrel (NG) and dienogest (DEG)] and of the pregnane type [chlormadinone acetate (CMA), progesterone (P)] on total cholesterol (TC) and high-density-lipoprotein cholesterol (HDL-C) in serum has been investigated in combination with estradiol (E). E increased TC (45%) and HDL-C (12%). NEA, NG and DEG alone decreased TC maximally by 58% and HDL-C maximally by 67%, CMA and P were without influence. In combination with E, the gestagens NEA, NG and DEG suppressed the E-induced increase of TC and HDL-C, whereas CMA and P did not counteract the TC increase. The effects of estrogen/gestagen combinations on HDL-C in the serum of rats are similar to those in men, but species differences in the lipoprotein metabolism must be taken into consideration.

Absence of Effect of Oral Rifaximin on the Pharmacokinetics of Ethinyl Estradiol/Norgestimate in Healthy Females

Rifaximin is an oral rifampin analog, and its activity is targeted within the gastrointestinal tract. Some analogs induce the cytochrome P450 family of oxidative enzymes. Ethinyl estradiol (EE), commonly found in oral contraceptives (OCs), is a known CYP3A4 substrate. To determine the potential effect of rifaximin on EE and norgestimate pharmacokinetics. In an open-label, crossover study, healthy females received a single dose of OC (EE 0.07 mg/norgestimate 0.50 mg). Following a 1 week washout period, individuals received rifaximin 200 mg every 8 hours for 3 days, with a single dose of OC administered with the ninth rifaximin dose. During both treatment periods, blood samples were collected periodically for up to 96 hours after each OC dose. Plasma concentration-time profiles and pharmacokinetic parameters were characterized for EE and 2 major metabolites of norgestimate, norgestrel (NG) and 17-deacetyl norgestimate (17-DNGM). A drug-drug interaction was confirmed if the 90% CI for the 2 treatment period comparison was outside the 80-125% limit. Twenty-six of 28 women completed the study. No differences in pharmacokinetic parameters were observed for EE, NG, or 17-DNGM when a single dose of the OC was administered alone or with rifaximin. In addition, the 90% CI for the bioavailability contrasts (OC alone vs OC with rifaximin) for the maximum plasma concentration, area under the plasma concentration-time curve from zero to the last measurable plasma concentration or to infinity for EE, NG, and 17-DNGM all ranged from 86-118%. These intervals were within the predefined range for equivalence; therefore, no interaction was observed between OC and rifaximin. Rifaximin was well tolerated. Administration of a 3 day dosing regimen of oral rifaximin was well tolerated and did not alter the pharmacokinetics of a commonly used combination OC containing EE and norgestimate.

The effect of rifaximin on the pharmacokinetics of a single dose of ethinyl estradiol and norgestimate in healthy female volunteers

Introduction Rifaximin (RFX) is a poorly absorbed, rifamycin S derived antibiotic with broad-spectrum bactericidal activity undergoing evaluation for the treatment of traveler's diarrhea. Objective: To evaluate the effect of RFX on the pharmacokinetics (PK) of active components of an oral contraceptive (OC). Methods: An open label, crossover design in 28 healthy female subjects to determine if oral RFX 200 mg Q8hr for 3 days alters the PK of a single dose of OC (ethinyl estradiol (EE)/norgestimate), given as two tablets (0.07 mg EE and 0.50 mg norgestimate). Subjects received a single dose of OC in Period A and after a one-week washout, a single PO dose of OC together with the 9th consecutive dose of RFX in Period B. Plasma for PK evaluation was harvested for 96 hr after each OC dose. Results: There were no significant differences in mean estimates of Cmax, AUC0-last, AUC0-inf, or PK variability for EE, norgestrel (NG), and 17-deacetylnorgestimate (NGMN) between periods (see Table). All study treatments were well tolerated. Conclusions: The PK of single doses of EE and norgestimate were not altered by RFX. It is expected that the efficacy of OCs would not be altered by concomitant administration of RFX. Clinical Pharmacology & Therapeutics (2004) 75, P96–P96; doi: 10.1016/j.clpt.2003.11.366 OC+RFX Period A OC+RFX Period B PK Parameters EE NG NGMN EE NG NGMN Cmax (ng/mL) 0.20 ± 0.06 1.03 ± 0.37 3.48 ± 0.98 0.19 ± 0.06 1.09 ± 0.48 3.40 ± 1.05 AUC0-last (ng.hr/mL) 1.97 ± 0.69 25.08 ± 13.59 34.30 ± 8.72 1.82 ±0.58 28.07 ±13.68/C> 36.05 ± 8.39 Half- life (h) 15.08 44.82 27.46 17.26 51.13 27.78