Treatment with Norgestrel (20 µM; 24 hours; 661W cells) dramatically improved cell survival following serum deprivation, indicating that Norgestrel had a neuroprotective impact on stressed 661W cells [1]. Norgestrel (20 µM; 24 hours; 661W cells) treatment decreases caspase-3 and PARP cleavage produced by apoptosis [1]. When photoreceptor cells are treated with Norgestrel (20 µM) for six hours, 661W cells exhibit a substantial increase of bFGF mRNA [1].

Treatment with norgestrel (100 mg/kg; i.p.; 6, 24, or 48 h; Balb/c mice) inhibited the production of ROS in response to light, which in turn stopped photoreceptor cell death. The primary antioxidant transcription factor Nrf2 is regulated post-translationally by norgestrel, which causes phosphorylation, nuclear translocation, and elevated levels of its effector protein, superoxide dismutase 2 (SOD2) [2].

Cell Viability Assay[1]
Cell Types: 661W Cell
Tested Concentrations: 20 µM
Incubation Duration: 24 hrs (hours)
Experimental Results: Cell viability increased Dramatically after serum deprivation.

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Western Blot Analysis[1]
Cell Types: 661W Cell
Tested Concentrations: 20 µM
Incubation Duration: 24 hrs (hours)
Experimental Results: diminished apoptosis-induced cleavage of PARP and caspase-3.

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RT-PCR[1]
Cell Types: 661W Cell
Tested Concentrations: 20 µM
Incubation Duration: 6 hrs (hours)
Experimental Results: bFGF mRNA was Dramatically upregulated within 1 hour.

Animal/Disease Models: balb/c (Bagg ALBino) mouse were born and maintained in dim circulating light [2]
Doses: 100 mg/kg;
Route of Administration: intraperitoneal (ip) injection; 6, 24 or 48 hrs (hrs (hours))
Experimental Results: Increased expression of Nrf2 via serine 40 phosphorylation and Activated, increases the expression of its target antioxidant superoxide dismutase 2 (SOD2), and reduces mitochondrial oxidative stress.

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Light Damage Model:** Balb/c mice were born and maintained in dim cyclic light (<10 lx, 12h on/12h off). At 4-7 weeks of age, mice were dark-adapted for 18 hours prior to light exposure. Mice received intraperitoneal injections of 50 μL vehicle (25 μL DMSO/25 μL peanut oil) or 50 μL norgestrel (100 mg/kg) 1 hour prior to light damage. Immediately before light exposure, pupils were dilated with 0.5% cyclopentolate under red light. Retinal light damage was induced by exposure to cool white fluorescent light (5000 lx) for 2 hours. After light exposure, mice were placed in the dark for 6, 24, or 48 hours prior to euthanasia by cervical dislocation. [2]
* **DHE Administration for ROS Detection:** Following light damage, mice received two intraperitoneal injections of 20 mg/kg dihydroethidium (DHE) 30 minutes apart, performed 3.5-4 hours prior to euthanasia under minimal light. Mice were returned to the dark until euthanasia. [2]
* **Tissue Collection:** Enucleated eyes were fixed in 4% paraformaldehyde for 1.5 hours, cryoprotected in 30% sucrose overnight at 4°C, frozen in Shandon Cryomatrix, and sectioned at 7 μm using a cryostat. Sections were stored at -80°C. [2]
* **Subcellular Fractionation:** Snap-frozen retinas (approximately 4 retinas per group per time point, pooled) were used for subcellular fractionation using a tissue-specific kit with Halt Protease and Phosphatase Inhibitor Cocktail. Cytosolic and nuclear fractions were prepared according to kit instructions. [2]

Absorption, Distribution and Excretion
Norethindrone is absorbed via the gastrointestinal tract, metabolized in the liver, and excreted in urine and feces as glucuronide and sulfate conjugates. In seven subjects administered 14C-norethindrone, 43% of the dose was excreted in urine over 5 days; the radioactive biological half-life is 24 hours. Enzymatic hydrolysis released only 32% of the urinary radioactivity, with another 25% excreted as sulfate conjugates. The metabolites excreted in urine are significantly less polar than those excreted after administration of the related compound norethindrone or acetylene. The 3αOH,5β and 3βOH,5β isomers of tetrahydronorethindrone (13β-ethyl-17α-ethynyl-5β-gonan-3α,17β-diol) were isolated from urine and identified by mass spectrometry, thin-layer chromatography, and gas-liquid chromatography. Plasma radioactivity decreased more rapidly after administration of norethindrone compared to administration of acetylene or acetylene. Approximately 2% of the administered dose is converted into acidic compounds. There was no significant difference in radioactive excretion rate or metabolites after oral or intravenous administration of norethindrone. The binding of different synthetic steroids (used for hormonal contraception) to SHBG was investigated by measuring their ability to displace tritium-labeled testosterone from sex hormone-binding globulin (SHBG) in a competitive protein binding system. Only 19-nortestosterone derivatives exhibited a significant ability to displace testosterone from SHBG, with dextroethindrone (d-Ng) showing the strongest displacement capacity. In women with previously stable plasma d-Ng levels, increasing SHBG levels resulted in a 2- to 6-fold increase in SHBG levels. This leads to the conclusion that SHBG is the primary carrier protein of d-Ng. The potent testosterone displacement activity of d-Ng may also explain the androgenic side effects observed in oral contraceptives containing d-Ng.

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Metabolism/Metabolites
(14) C-norethindrone was administered to 7 subjects, and 43% of the dose was excreted in the urine over 5 days…Enzymatic hydrolysis released only 32% of the urinary radioactivity, with another 25% excreted as sulfate conjugates. The metabolites excreted in the urine were much less polar than those produced after administration of the related compound norethindrone or its metabolites. The 3αOH,5β and 3βOH,5β isomers of tetrahydronorethindrone (13β-ethyl-17α-ethynyl-5β-gonan-3α,17β-diol) were isolated from the urine and identified by mass spectrometry, thin-layer chromatography, and gas-liquid chromatography. Plasma radioactivity decreased more rapidly after administration of norethindrone than after administration of norethindrone or its metabolites. Approximately 2% of the administered dose was converted to acidic compounds. There was no significant difference in the rate of radioactive excretion or metabolites after oral or intravenous administration of norethindrone. The metabolism of dl-, d-, and l-norethindrone was investigated in African green monkeys (Cercopithecus aethiops). Following a single oral administration of 14C-dl-norethindrone (1 mg/kg), the total urinary excretion of 14C (51.4 ± 5.0%) was significantly higher than that following administration of the d-enantiomer (37.5 ± 5.4%), but not significantly different from that following administration of the l-enantiomer (44.2 ± 8.9%). In all cases, the majority of the radioactive material in the urine was in free form (48–62%), with an additional 13–27% released by β-glucuronidase preparations. Sulfate conjugates were not detected. At least one major metabolic pathway (16β-hydroxylation) and one minor metabolic pathway (16α-hydroxylation) exhibit stereoselectivity, meaning they are effective for the 14I-enantiomer but not for the d-enantiomer. The three metabolites, 16β-hydroxynorethindrone, 16α-hydroxynorethindrone, and 16-hydroxytetrahydronorethindrone (believed to be 16β), were detected only in urine samples from animals administered 14Cdl-norethindrone. Following administration of 14Cd-norethindrone, 3α,5β-tetrahydronorethindrone was found to be the major urinary metabolite. These observations were compared with previously reported results regarding the metabolism of dl-norethindrone in female urine. The in vitro metabolism of norethindrone stereoisomers (d, l, and a racemic mixture of dl) by rabbit liver microsomal fractions was investigated. The bioactive 1-norethindrone is metabolized faster than the inactive d-norethindrone. This is primarily because levonorgestrel is more readily converted to its A-ring reducing metabolite. There was no difference in the degree of hydroxylation between the two isomers; after 30 minutes of incubation, approximately 40% of each isomer was converted to its hydroxylated metabolite. However, differences existed between the two isomers: levonorgestrel was primarily converted to 16β-hydroxysteroids, while dextroethingestrel was converted to 16α-hydroxysteroids. The amount of hydroxylation at the C-6 position was similar for both isomers. The metabolism of the racemic mixture was intermediate between that of the levonorgestrel and dextroethingestrel isomers. The rates of in vitro metabolism of 19-nortestosterone-derived synthetic progestins from rabbit liver tissue were compared. Within 1 hour, the metabolic rate of norethindrone was comparable to that of 19-nortestosterone, while the metabolic rates of dextroethingestrel and norethindrone were slightly lower. The metabolic rate of levonorgestrel was less than 5%. In all cases, the reaction product was a tetrahydrosteroid. Norethindrone is metabolized via levonorgestrel. Skeletal muscle, lungs, and the small intestine also metabolize norethindrone and dextrogestrel, but at a slower rate than liver tissue. Adipose tissue metabolizes small amounts of norethindrone, but the heart and spleen do not. In any of the extrahepatic tissues studied, neither norethindrone nor levonorgestrel was metabolized.
An in vitro study investigated the metabolism of three steroids used in oral contraceptives (OCs) using a small amount of human jejunal mucosa. This study was conducted because the human gastrointestinal mucosa is known to metabolize a variety of drugs. After incubation, approximately 40% of ethinylestradiol, 9.8% of levonorgestrel, and 7% of ethinylestradiol were metabolized. All of these metabolic responses were significantly different from the control group. The results indicate that ethinylestradiol metabolism is related to the weight of the tissue used. These results are consistent with the known significant first-pass effect of ethinylestradiol. Norethindrone, which is known to have a small or no first-pass effect, also has a low intestinal metabolic rate. Under the experimental conditions used, phase I metabolism of ethinylestradiol or levonorgestrel was not observed.
Hepatic metabolism.
Excretion pathway: Approximately 45% of levonorgestrel and its metabolites are excreted in urine and approximately 32% in feces, primarily as glucuronide conjugates.

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Biological half-life
(14) C-norethindrone was administered to 7 subjects, and 43% of the dose was excreted in urine within 5 days; the biological half-life of the radioactive material is 24 hours.

Toxicity Summary
Binding to progesterone and estrogen receptors. Target cells include the female reproductive tract, mammary glands, hypothalamus, and pituitary gland. Once progestins (such as levonorgestrel) bind to their receptors, they slow the release frequency of hypothalamic gonadotropin-releasing hormone (GnRH) and inhibit the pre-ovulatory surge of luteinizing hormone (LH). Toxicity Data
LD50 >5000 mg/kg (oral administration in rats) Interactions Concomitant use with substances known to induce drug-metabolizing enzymes (especially cytochrome P450 enzymes), such as anticonvulsants (e.g., phenobarbital, phenytoin, carbamazepine) and anti-infectives (e.g., rifampin, rifabutin, nevirapine, efavirenz), may increase the metabolism of estrogen and progesterone. Ritonavir and nelfinavir, while known potent inhibitors, exhibit induction when used concomitantly with these drugs. When used concomitantly with steroid hormones, herbal preparations containing Hypericum perforatum may induce the metabolism of estrogen and progesterone. Phenytoin and rifampin increase serum concentrations of sex hormone-binding globulin (SHBG); this significantly reduces the serum concentrations of free drug of certain progestins, a concern particularly for patients using progestin for contraception. /Progestins/ Currently, there are no data on drug interactions with rifabutin, but due to its structural similarity to rifampin, similar precautions may be necessary when used concomitantly with progestins. ... /Progestins/

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Non-human toxicity values
Rats oral LD50 5010 mg/kg
Rats intraperitoneal LD50 11,200 mg/kg
Mice intraperitoneal LD50 7300 mg/kg
Mice oral LD50 5010 mg/kg

[1]. The synthetic progesterone Norgestrel is neuroprotective in stressed photoreceptor-like cellsand retinal explants, mediating its effects via basic fibroblast growth factor, protein kinase A and glycogen synthase kinase 3β signalling. Eur J Neurosci. 2016 Apr;43(7):899-911.

[2]. The synthetic progestin norgestrel modulates Nrf2 signaling and acts as an antioxidant in a model of retinal degeneration. Redox Biol. 2016 Dec;10:128-139.

Therapeutic Uses

Oral synthetic contraceptive; synthetic progestin
Low-dose norethindrone (norethindrone and ethinylestradiol tablets) is indicated for women who choose to use this product as a method of contraception to prevent pregnancy. /US product label contains/
/Cyproterone is indicated for/hormone replacement therapy (HRT) for symptoms of estrogen deficiency in perimenopausal and postmenopausal women.
/Cyproterone is indicated for/prevention of osteoporosis in postmenopausal women at high risk of future fractures who cannot tolerate or are contraindicated in using other approved medications for the prevention of osteoporosis.
Norethindrone…/is indicated for/prevention of pregnancy. Progestin-only oral contraceptives are also known as mini contraceptives or progestin-only oral contraceptives (POPs). /Before/
Drug Warnings
Smoking increases the risk of serious cardiovascular side effects after taking oral contraceptives. This risk increases with age and the amount of smoking (15 cigarettes or more per day), and is particularly pronounced in women over 35 years of age. Women taking oral contraceptives are strongly advised not to smoke.
Taking oral contraceptives increases the risk of several serious illnesses, including myocardial infarction, thromboembolism, stroke, liver tumors, and gallbladder disease. However, the risk of serious illness or death is very small for healthy women without underlying risk factors. Morbidity and mortality increase significantly if other underlying risk factors such as hypertension, hyperlipidemia, hypercholesterolemia, obesity, and diabetes are present.
Women should not use oral contraceptives if they have: thrombophlebitis or thromboembolic disease; a history of deep vein thrombosis or thromboembolic disease; cerebrovascular or coronary artery disease; known or suspected breast cancer; endometrial cancer or other known or suspected estrogen-dependent tumors; unexplained abnormal genital bleeding; cholestatic jaundice during pregnancy or jaundice that has occurred after previous use of oral contraceptives; hepatic adenoma, liver cancer, or benign liver tumors; or known or suspected pregnancy.
The most common adverse reaction to oral contraceptives is nausea. Nausea has also been reported in women using vaginal or transdermal estrogen-progestin contraceptives. The main risk of the currently recommended high-dose postcoital estrogen-progestin combination regimen appears to be moderate to severe gastrointestinal adverse reactions, including severe vomiting and nausea, occurring in 12-22% and 30-66% of women receiving short courses, respectively, which may limit patient adherence and treatment efficacy. In two prospective randomized studies, the incidence of nausea and vomiting was lower with the high-dose postcoital progestin monotherapy regimen (0.75 mg levonorgestrel twice every 12 hours) compared to the high-dose estrogen-progestin combination regimen (100 mcg ethinylestradiol and 0.5 mg levonorgestrel twice every 12 hours). Other gastrointestinal adverse reactions include vomiting, abdominal cramps, abdominal pain, bloating, diarrhea, and constipation. Gingivitis and dry socket have also been reported. Changes in appetite and weight may also occur. /Estrogen-Progestin Combination Preparations/
For more complete data on drug warnings for NORGESTREL (52 items), please visit the HSDB record page.

C21H28O2

312.453

312.208

6533-00-2

13109

White to off-white solid powder

1.1±0.1 g/cm3

459.1±45.0 °C at 760 mmHg

239-241ºC

195.4±21.3 °C

0.0±2.6 mmHg at 25°C

1.571

3.92

1

2

2

23

609

6

CC[C@@]12CC[C@@H]3C4CCC(=O)C=C4CC[C@H]3[C@@H]2CC[C@]1(C#C)O

WWYNJERNGUHSAO-XUDSTZEESA-N

InChI=1S/C21H28O2/c1-3-20-11-9-17-16-8-6-15(22)13-14(16)5-7-18(17)19(20)10-12-21(20,23)4-2/h2,13,16-19,23H,3,5-12H2,1H3/t16-,17+,18+,19-,20-,21-/m0/s1

(8R,9S,10R,13S,14S,17R)-13-ethyl-17-ethynyl-17-hydroxy-1,2,6,7,8,9,10,11,12,14,15,16-dodecahydrocyclopenta[a]phenanthren-3-one

Norgestrel SH 850 SH 70850

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~100 mg/mL (~320.05 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (8.00 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (8.00 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (8.00 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)