DEPO-ESTRADIOL
Clinical safety rating: avoid
Inducers of CYP450 enzymes (eg carbamazepine) may decrease estrogen levels Increases risk of thromboembolic disorders and endometrial cancer.
Estradiol is an estrogen hormone that binds to estrogen receptors (ERα and ERβ) in target tissues, modulating gene transcription and exerting effects such as proliferation of endometrial tissue, regulation of gonadotropin secretion (negative feedback on FSH and LH), and maintenance of secondary sexual characteristics.
| Metabolism | Primarily hepatic metabolism via cytochrome P450 enzymes, mainly CYP3A4 and CYP1A2, to estrone and estriol. Undergoes enterohepatic recirculation and conjugation (glucuronidation and sulfation). Metabolites are excreted primarily in urine. |
| Excretion | Estradiol is extensively metabolized in the liver, with conjugated metabolites (glucuronides and sulfates) primarily excreted in urine (about 90%) and feces (about 10%). Less than 5% is excreted unchanged. |
| Half-life | The terminal elimination half-life of estradiol after intramuscular injection of Depo-Estradiol is approximately 5-9 days, reflecting slow release from the depot and prolonged systemic exposure. |
| Protein binding | Approximately 98-99% bound, primarily to sex hormone-binding globulin (SHBG) and albumin. |
| Volume of Distribution | The volume of distribution is approximately 1.1 L/kg, indicating extensive distribution into tissues. |
| Bioavailability | Intramuscular administration provides 100% bioavailability due to complete absorption from the injection site. |
| Onset of Action | After intramuscular injection, clinical effects (e.g., relief of menopausal symptoms) are typically observed within 2-4 hours. |
| Duration of Action | Duration of action after a single intramuscular dose is approximately 3-4 weeks, due to sustained release from the injection site and enterohepatic recirculation. |
1 to 5 mg intramuscularly every 3 to 4 weeks for estrogen replacement therapy.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment. |
| Liver impairment | Contraindicated in severe hepatic disease; for Child-Pugh A or B, initiate at lowest dose and titrate cautiously. |
| Pediatric use | Not indicated for use in pediatric patients; safety and efficacy not established. |
| Geriatric use | Initiate at lowest effective dose; monitor for thromboembolic events and estrogen-sensitive malignancies. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Inducers of CYP450 enzymes (eg carbamazepine) may decrease estrogen levels Increases risk of thromboembolic disorders and endometrial cancer.
| FDA category | Positive |
| Breastfeeding | Estradiol is excreted into breast milk in low amounts. The M/P ratio is not established. It may reduce milk production and composition, particularly with high doses. The American Academy of Pediatrics considers estradiol compatible with breastfeeding, but caution is advised due to potential effects on the infant (e.g., gynecomastia, vaginal discharge in female infants). Use only if clearly needed and monitor infant for adverse effects. |
■ FDA Black Box Warning
Estrogens increase the risk of endometrial cancer in postmenopausal women with an intact uterus. Estrogens should not be used to prevent cardiovascular disease or dementia. The Women's Health Initiative (WHI) substudy reported increased risks of stroke, deep vein thrombosis, pulmonary embolism, and myocardial infarction in postmenopausal women (50-79 years of age) treated with conjugated estrogens. The WHI Memory Study (WHIMS) reported increased risk of probable dementia in postmenopausal women over 65 years of age treated with conjugated estrogens.
| Common Effects | osteoporosis prevention |
| Serious Effects |
Known or suspected pregnancy, undiagnosed abnormal genital bleeding, known or suspected breast cancer (except in selected palliative cases), known or suspected estrogen-dependent neoplasia, active thromboembolic disorders or history of these conditions (e.g., DVT, PE), history of thrombophlebitis associated with estrogen use, hepatic impairment or disease as long as liver function tests have not returned to normal, known hypersensitivity to estradiol or any component of the formulation.
| Precautions |
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| Teratogenic Risk |
| Estradiol is contraindicated in pregnancy. First trimester exposure is associated with a potential risk of congenital anomalies, including cardiovascular and limb defects, based on observational studies. Second and third trimester exposure may lead to urogenital tract abnormalities in female offspring and potential long-term reproductive effects. Use during pregnancy has been linked to an increased risk of vaginal adenocarcinoma in female offspring (in utero DES exposure, a related estrogen). Animal studies show embryotoxicity and teratogenicity at clinically relevant doses. |
| Fetal Monitoring | If inadvertent exposure during pregnancy occurs, monitor fetal development via high-resolution ultrasound and echocardiography. Monitor maternal blood pressure, glucose, and lipid profiles. Assess for signs of thromboembolism, especially if coexisting risk factors. Serial growth scans in later pregnancy if continued exposure. |
| Fertility Effects | Estradiol may impair fertility by suppressing gonadotropins and ovulation at high doses. It is used in some assisted reproductive protocols but can also disrupt natural menstrual cycles. Reversible upon discontinuation. Chronic use may delay return to fertility. |
| Cardiovascular disorders (e.g., stroke, MI, thromboembolism), malignancy (endometrial, breast), dementia, gallbladder disease, hypercalcemia, visual abnormalities, fluid retention, elevated blood pressure, hypertriglyceridemia, hypothyroidism, hereditary angioedema, exacerbation of endometriosis, and pregnancy (category X). Monitor for signs of thrombosis, abnormal uterine bleeding, and hepatic impairment. |