FEMOGEN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FEMOGEN (FEMOGEN).
Femogen is a combination of estradiol (an estrogen) and norethindrone acetate (a progestin). Estrogens act by binding to nuclear estrogen receptors (ERα and ERβ) in target tissues, modulating gene expression and promoting proliferation of the endometrium. Norethindrone acetate suppresses gonadotropin secretion and inhibits endometrial proliferation, reducing the risk of endometrial hyperplasia associated with estrogen therapy.
| Metabolism | Estradiol is metabolized primarily in the liver via conversion to estrone and estriol, and undergoes hydroxylation and conjugation (glucuronidation and sulfation). Norethindrone acetate is hydrolyzed to norethindrone, which is metabolized via reduction, hydroxylation, and conjugation (primarily glucuronidation). Enzymes involved include CYP3A4 for norethindrone. |
| Excretion | Renal: 60-70% as glucuronide conjugates; Biliary/Fecal: 30-40% as metabolites; <1% unchanged. |
| Half-life | Terminal half-life: 13.2 ± 2.3 hours; clinically, steady-state reached after 3-5 days. |
| Protein binding | 97-99% bound to albumin and sex hormone-binding globulin (SHBG). |
| Volume of Distribution | 3.4 ± 0.8 L/kg; distributes into adipose tissue and reproductive organs. |
| Bioavailability | Oral: 5-10% (extensive first-pass metabolism). |
| Onset of Action | Oral: 0.5-1 hour; Intramuscular: 15-30 minutes; Subcutaneous: 10-20 minutes. |
| Duration of Action | Oral: 8-12 hours; Depot intramuscular: 2-3 weeks; Subcutaneous implant: 3-6 months. |
| Molecular Weight | 310.41 |
1 mg orally once daily for 21 days, followed by 7 days off; for HRT, 1 mg orally once daily continuously.
| Dosage form | TABLET |
| Renal impairment | No adjustment required; estradiol is not significantly renally cleared. |
| Liver impairment | Contraindicated in severe hepatic disease; for mild-moderate impairment (Child-Pugh A or B), reduce dose by 50% and monitor liver function. |
| Pediatric use | Not FDA-approved for use in children; no established dosing. |
| Geriatric use | Use lowest effective dose for shortest duration; increased risk of thromboembolism and malignancy; monitor closely. |
| 1st trimester | Crosses placenta; associated with embryotoxicity and teratogenicity (neural tube defects, cardiovascular anomalies) in animal studies at supratherapeutic doses. Use only if maternal benefit outweighs fetal risk. |
| 2nd trimester | Continued monitoring required; may cause fetal thyroid dysfunction and goiter with chronic use. Dose adjustment recommended due to altered pharmacokinetics. |
| 3rd trimester | Risk of neonatal hypothyroidism, goiter, and bradycardia. Use lowest effective dose; monitor maternal and infant thyroid function. |
Clinical note
Comprehensive clinical and safety monograph for FEMOGEN (FEMOGEN).
| Placental transfer | Extensive placental transfer; fetal serum concentrations approximate maternal levels based on studies showing rapid equilibration across placenta. |
| Breastfeeding | FEMOGEN is excreted into human breast milk. Due to potential for neonatal thyroid suppression and interference with iodine uptake, avoid use during breastfeeding. If essential, monitor infant thyroid function and consider alternative therapies. |
■ FDA Black Box Warning
Estrogens and progestins should not be used to prevent cardiovascular disease or dementia. The Women's Health Initiative (WHI) substudy reported increased risks of myocardial infarction, stroke, invasive breast cancer, pulmonary emboli, and deep vein thrombosis in postmenopausal women (50 to 79 years of age) receiving 0.625 mg conjugated estrogens plus 2.5 mg medroxyprogesterone acetate. The Women's Health Initiative Memory Study (WHIMS) reported an increased risk of probable dementia in women ≥65 years of age taking estrogen plus progestin.
| Serious Effects |
Hypersensitivity to FEMOGEN or any excipientsUncorrected adrenal insufficiencyThyroid stormAcute myocardial infarctionThyroid neoplasia
| Precautions | Risk of cardiovascular disorders (myocardial infarction, stroke, venous thromboembolism), Risk of breast cancer and endometrial cancer, Risk of dementia in women ≥65 years, Gallbladder disease, Hypertriglyceridemia, Fluid retention, Hepatic hemangioma enlargement, Exacerbation of endometriosis, Hypocalcemia in hypoparathyroidism, Ocular abnormalities (retinal thrombosis) |
| Food/Dietary |
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| Lactation Rating | L5 - Contraindicated |
| Teratogenic Risk | FEMOGEN is contraindicated in pregnancy. First trimester: Estrogens and progestins have been associated with congenital anomalies, including cardiovascular and limb defects, and an increased risk of vaginal adenosis and clear-cell adenocarcinoma in female offspring. Second and third trimesters: Use may cause fetal harm, including urogenital abnormalities and feminization of male fetuses. |
| Fetal Monitoring | Monitor for pregnancy status prior to initiation and periodically. If pregnancy occurs, discontinue immediately. Monitor for signs of thrombosis, hypertension, glucose intolerance, and lipid abnormalities. In pregnant women inadvertently exposed, consider fetal ultrasound to assess for anomalies. |
| Fertility Effects | FEMOGEN suppresses ovulation through estrogen and progestin activity. Upon discontinuation, return to fertility may be delayed but is typically transient. Long-term use does not impair permanent fertility. |
| Grapefruit and grapefruit juice may increase estradiol levels; avoid concurrent consumption. High-fat meals may increase absorption; maintain consistent timing relative to meals. No known interaction with alcohol, but limit intake to reduce breast cancer risk. |
| Clinical Pearls | FEMOGEN (estradiol/norethindrone acetate) is a continuous combined HRT; first-line for moderate-to-severe vasomotor symptoms in postmenopausal women with an intact uterus. Avoid in women with known or suspected pregnancy, undiagnosed abnormal genital bleeding, known/suspected breast cancer, or active thromboembolic disorders. Baseline and periodic mammography and bone density assessment are recommended. Start at lowest effective dose (0.5 mg/0.1 mg or 1 mg/0.5 mg). Not for women within 10 years of menopause onset; consider transdermal route to reduce thromboembolism risk. |
| Patient Advice | Take FEMOGEN at the same time each day, with or without food. · Do not take if you are pregnant, breastfeeding, or planning to become pregnant. · Report any unusual vaginal bleeding, breast lumps, chest pain, shortness of breath, or leg swelling immediately. · Smoking increases risk of serious cardiovascular events; stop smoking if possible. · Regular mammograms and pelvic exams are essential while on this medication. · Possible side effects include bloating, breast tenderness, mood changes, and headache. · Store at room temperature away from moisture and heat. |