FEMHRT
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FEMHRT (FEMHRT).
FEMHRT is a combination of ethinyl estradiol and norethindrone acetate. Ethinyl estradiol is an estrogen that binds to estrogen receptors, promoting proliferation of the endometrium and other estrogen-responsive tissues. Norethindrone acetate is a progestin that binds to progesterone receptors, causing secretory changes in the endometrium and inhibiting gonadotropin release from the pituitary, thereby suppressing ovulation.
| Metabolism | Ethinyl estradiol is metabolized primarily by CYP3A4, with minor contributions from CYP2C9 and CYP2C19. Norethindrone acetate is metabolized by CYP3A4. |
| Excretion | Estradiol: primarily renal (60-80% as conjugates, primarily glucuronides and sulfates), fecal (10-20%). Norethindrone: primarily renal (60-70% as metabolites), fecal (30-40%). |
| Half-life | Estradiol: terminal half-life approximately 24 hours due to enterohepatic recirculation. Norethindrone: terminal half-life approximately 8-11 hours. |
| Protein binding | Estradiol: 97-99% bound, primarily to sex hormone-binding globulin (SHBG) and albumin. Norethindrone: 95-99% bound, primarily to albumin and SHBG. |
| Volume of Distribution | Estradiol: Vd ~1.2 L/kg, indicating extensive tissue distribution. Norethindrone: Vd ~4.0 L/kg, indicating wide distribution into tissues. |
| Bioavailability | Estradiol: oral bioavailability approximately 5-10% due to extensive first-pass metabolism. Norethindrone: oral bioavailability approximately 64% (range 50-80%). |
| Onset of Action | Oral: estradiol effects on vasomotor symptoms begin within 2-4 weeks; progestin effects on endometrium within days. |
| Duration of Action | Steady state achieved within 5-7 days; continuous daily dosing maintains therapeutic levels. Withdrawal bleeding may occur during placebo week if used cyclically. |
One tablet (estradiol 1 mg/norethindrone acetate 0.5 mg) orally once daily
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment; use with caution in severe renal impairment (GFR <30 mL/min) due to potential accumulation of excipients |
| Liver impairment | Contraindicated in patients with hepatic impairment or disease; no specific Child-Pugh based dose recommendations |
| Pediatric use | Not indicated for use in pediatric patients |
| Geriatric use | Use lowest effective dose for shortest duration; monitor for thromboembolic events, cardiovascular disease, and malignancy; limited data in women >65 years |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FEMHRT (FEMHRT).
| Breastfeeding | Estradiol and norethindrone are excreted in human milk in small amounts; estimated infant dose <1% of maternal weight-adjusted dose. M/P ratio for estradiol is approximately 0.02; for norethindrone, M/P ratio is approximately 0.001. Use during lactation may reduce milk quantity and quality. Breastfeeding is not recommended during therapy, especially in the first 6 weeks postpartum. Consider alternative contraception or discontinuation of breastfeeding if FEMHRT is necessary. |
| Teratogenic Risk | FEMHRT contains estradiol and norethindrone acetate. Estrogens are not recommended during pregnancy; first-trimester exposure may be associated with a small increased risk of congenital anomalies (e.g., cardiovascular defects). Second- and third-trimester exposure may increase risk of reproductive tract abnormalities and urogenital tumors in offspring. Norethindrone acetate, a progestin, may cause fetal harm, including ambiguous genitalia in female fetuses and hypospadias in male fetuses with first-trimester exposure. Progestins have been associated with cardiovascular and other defects. Use is contraindicated in pregnancy. |
■ FDA Black Box Warning
Estrogens plus progestins should not be used for the prevention of cardiovascular disease or dementia. The Women's Health Initiative (WHI) estrogen plus progestin substudy reported increased risks of stroke, deep vein thrombosis, pulmonary embolism, and myocardial infarction in postmenopausal women. The WHI memory study reported increased risk of probable dementia in postmenopausal women 65 years of age or older.
| Serious Effects |
Undiagnosed abnormal genital bleeding, known/suspected breast cancer, known/suspected estrogen-dependent neoplasia, active or past thromboembolic disorders (e.g., DVT, PE, stroke, MI), liver disease or impaired liver function, known or suspected pregnancy, hypersensitivity to any component.
| Precautions | Cardiovascular disorders (stroke, MI, thromboembolism), breast cancer (increased risk with long-term use), endometrial cancer (risk reduced with progestin addition), dementia (increased risk in women ≥65 years), gallbladder disease, visual abnormalities (retinal thrombosis), elevated blood pressure, hypertriglyceridemia, hepatic hemangiomas, fluid retention, hereditary angioedema, and exacerbation of endometriosis. |
| Food/Dietary |
Loading safety data…
| Fetal Monitoring | No specific fetal monitoring indicated if accidental exposure occurs; however, pregnancy testing should be performed prior to initiation and at regular intervals during therapy. Monitor maternal blood pressure, serum lipids, and glucose as estrogens can affect these parameters. Assess for signs of thromboembolism (e.g., leg pain, chest pain, shortness of breath) due to increased risk with estrogen use. |
| Fertility Effects | FEMHRT suppresses gonadotropins and may suppress ovulation, acting as a hormonal contraceptive. It reversibly reduces fertility. Upon discontinuation, return to ovulation and normal fertility may be delayed but is expected within a few months. |
| Grapefruit and grapefruit juice may increase estrogen levels and risk of side effects; avoid concurrent use. High-fat meals can increase absorption of conjugated estrogens; take with food to reduce GI upset. Alcohol may worsen estrogen-related side effects like nausea and breast tenderness; limit intake. |
| Clinical Pearls | FemHRT contains conjugated estrogens (0.625 mg) and medroxyprogesterone acetate (5 mg). It is indicated for menopausal symptoms and osteoporosis prevention in women with an intact uterus. Initiate at the lowest effective dose for the shortest duration. Assess cardiovascular and thromboembolic risks prior to use. Do not use in women with undiagnosed abnormal genital bleeding, known/suspected breast cancer, active DVT/PE, or history of arterial thromboembolic disease. Monitor for endometrial hyperplasia, breast tenderness, and mood changes. |
| Patient Advice | Take exactly as prescribed; do not skip doses or stop without consulting your doctor. · This medication may increase risk of blood clots, stroke, heart attack, and breast cancer. · Report any abnormal vaginal bleeding, chest pain, leg swelling/pain, sudden severe headache, or visual changes immediately. · Avoid smoking, as it increases cardiovascular risks with hormone therapy. · Use non-hormonal contraception if needed, as FemHRT does not prevent pregnancy. · Inform all healthcare providers that you are taking FemHRT before any surgery or lab tests. |