PREMPRO/PREMPHASE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PREMPRO/PREMPHASE (PREMPRO/PREMPHASE).
Prempro/Premphase contains conjugated estrogens (CE) and medroxyprogesterone acetate (MPA). Estrogens bind to estrogen receptors (ERα/ERβ), activating genomic and non-genomic signaling, promoting proliferation of estrogen-responsive tissues, and modulating lipid metabolism. MPA is a progestin that binds to progesterone receptors, antagonizing estrogen-induced endometrial hyperplasia and blunting estrogen effects on breast tissue. The combination suppresses gonadotropin secretion via negative feedback on the hypothalamic-pituitary axis.
| Metabolism | Conjugated estrogens are primarily metabolized in the liver via CYP3A4 to hydroxylated and conjugated metabolites (e.g., estrone, estriol). Medroxyprogesterone acetate is metabolized via reduction, hydroxylation, and conjugation, with CYP3A4 playing a minor role. Both undergo enterohepatic recirculation and are excreted in urine (primarily as glucuronide and sulfate conjugates). |
| Excretion | Renal (90-95% as glucuronide and sulfate conjugates; <5% unchanged), biliary/fecal (5-10%). |
| Half-life | Conjugated estrogens: 10-24 hours (terminal, prolonged in hepatic impairment). Medroxyprogesterone acetate: 12-17 hours (terminal). |
| Protein binding | Estrogens: 98-99% bound to albumin and sex hormone-binding globulin (SHBG). Medroxyprogesterone acetate: 90-95% bound to albumin. |
| Volume of Distribution | Estrogens: 5-10 L/kg (large, indicating extensive tissue distribution, including adipose and reproductive tissues). Medroxyprogesterone acetate: 31-35 L (approximately 0.4-0.5 L/kg, distribution into breast and uterine tissues). |
| Bioavailability | Oral: 40-60% (estrogens undergo first-pass metabolism; medroxyprogesterone acetate: 100% absorbed, but first-pass reduces systemic availability to ~95% for the progestin component). |
| Onset of Action | Oral: Symptom relief within 2-4 weeks (vasomotor symptoms); endometrial protection within 10-14 days of progestin phase. |
| Duration of Action | Oral: 24 hours (daily dosing required for continuous hormone levels); progestin phase duration is 10-14 days per cycle (Premphase) or continuous (Prempro). |
Conjugated estrogens 0.625 mg/medroxyprogesterone acetate 2.5 mg (Prempro) or 0.625 mg/5 mg (Premphase) orally once daily.
| Dosage form | Tablet |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment; use caution in severe renal impairment due to potential accumulation of excipients. |
| Liver impairment | Contraindicated in severe hepatic disease (Child-Pugh class C). For mild to moderate impairment (Child-Pugh A or B), no specific dose adjustment is recommended but monitor hepatic function. |
| Pediatric use | Not indicated for use in pediatric patients. |
| Geriatric use | Use lowest effective dose for shortest duration; increased risk of dementia, breast cancer, and thromboembolic events. Consider alternative treatments. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PREMPRO/PREMPHASE (PREMPRO/PREMPHASE).
| Breastfeeding | Contraindicated during breastfeeding. Estrogens are excreted in human milk; M/P ratio not established. Potential for serious adverse effects in nursing infants, including hypercalcemia and jaundice. Discontinue drug or discontinue nursing. |
| Teratogenic Risk | Pregnancy Category X. First trimester: Use associated with congenital anomalies including cardiovascular and CNS defects. Second and third trimesters: In utero exposure linked to vaginal adenosis, clear cell adenocarcinoma in female offspring; also increased risk of urogenital abnormalities and functional disorders. |
■ FDA Black Box Warning
Estrogens plus progestin therapy should not be used for the prevention of cardiovascular disease. The Women's Health Initiative (WHI) substudy reported increased risks of myocardial infarction, stroke, invasive breast cancer, pulmonary emboli, and deep vein thrombosis. The risk of dementia was increased in postmenopausal women aged 65 years or older.
| Serious Effects |
["Undiagnosed abnormal genital bleeding","Known, suspected, or history of breast cancer","Known or suspected estrogen-dependent neoplasia (e.g., endometrial cancer)","Active or past venous thromboembolism (e.g., DVT, PE)","Active or past arterial thromboembolism (e.g., stroke, MI)","Known thrombophilic disorders (e.g., protein C/S deficiency, antithrombin deficiency)","Known or suspected pregnancy","Severe hepatic impairment or disease","Hypersensitivity to any component of Prempro/Premphase"]
| Precautions | ["Cardiovascular disorders: Increased risk of stroke, DVT, and MI. Discontinue if thrombotic events occur.","Malignant neoplasms: Increased risk of endometrial cancer (when used without progestin) and breast cancer (with progestin).","Dementia: Increased risk in women ≥65 years.","Gallbladder disease: Increased risk.","Hypertriglyceridemia: May cause pancreatitis if triglycerides are elevated.","Fluid retention: Caution in conditions exacerbated by edema (e.g., cardiac/renal impairment).","Hypocalcemia: May occur in patients with hypoparathyroidism.","Ocular effects: Discontinue if sudden vision loss or retinal thrombosis occurs.","Exacerbation of endometriosis: May occur with estrogen use.","Hereditary angioedema: Estrogens may induce or exacerbate symptoms."] |
Loading safety data…
| Fetal Monitoring | Not indicated for use in pregnant women. If inadvertent exposure occurs, monitor fetal development with ultrasound and consider amniocentesis for karyotype. Monitor for maternal thromboembolic events, hypertension, and hepatic effects. |
| Fertility Effects | May suppress ovulation via hormonal feedback inhibition. Use for contraception is not indicated; unintended pregnancy risk with concurrent progestin. Reversible upon discontinuation; no permanent impairment of fertility documented. |