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). |
| Molecular Weight | Estrogenic components: average 324.5 Da (estrone sulfate ~349 Da, equilin sulfate ~353 Da); medroxyprogesterone acetate: 386.5 Da. Overall, the active moieties are low molecular weight and capable of placental transfer. |
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 | Use is contraindicated in pregnancy. Estrogens and progestins are associated with fetal harm. Data suggest increased risk of congenital anomalies, including cardiovascular and central nervous system defects. |
| 2nd trimester | Contraindicated. Continued use may cause adverse fetal effects, including potential urogenital abnormalities and altered reproductive tract development. |
| 3rd trimester | Contraindicated. Use may lead to fetal feminization, urogenital abnormalities, and potential long-term health risks. Estrogens can delay parturition and cause oligohydramnios. |
Clinical note
Comprehensive clinical and safety monograph for PREMPRO/PREMPHASE (PREMPRO/PREMPHASE).
| Placental transfer | Estrogens and progestins readily cross the placenta. Conjugated estrogens and medroxyprogesterone acetate have documented placental transfer with measurable fetal serum concentrations. Degree of transfer varies but can achieve clinically significant levels. |
| Breastfeeding |
■ 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 |
PregnancyUndiagnosed abnormal genital bleedingKnown or suspected breast cancerKnown or suspected estrogen-dependent neoplasiaActive or history of venous thromboembolism (e.g., deep vein thrombosis, pulmonary embolism)Active or history of arterial thromboembolism (e.g., stroke, myocardial infarction)Known protein C, protein S, or antithrombin deficiency, or other thrombophilic disordersLiver disease or impaired liver functionKnown hypersensitivity to estrogens, progestins, or any component of the product
| 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…
| Excreted into breast milk. Estrogens and progestins can reduce milk production and affect composition. Use is not recommended during breastfeeding due to potential adverse effects on the infant, including hormonal disturbances. If use is necessary, minimize infant exposure through timing and dosage adjustments. |
| Lactation Rating | L5 |
| 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. |
| 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. |
| Food/Dietary | Grapefruit juice may increase estrogen levels and risk of adverse effects. Avoid high-fat meals as they may increase absorption of conjugated estrogens. Calcium and vitamin D supplements are often recommended concurrently. |
| Clinical Pearls | Prempro (conjugated estrogens/medroxyprogesterone acetate continuous combined) and Premphase (conjugated estrogens/medroxyprogesterone acetate sequential) are hormone therapy for postmenopausal women with an intact uterus. Avoid in women with a history of breast cancer, thromboembolic disorders, or unexplained vaginal bleeding. Use the lowest effective dose for the shortest duration. Monitor for endometrial hyperplasia. Premphase uses a 28-day cycle: days 1-14: estrogen alone; days 15-28: estrogen plus progestin. Prempro is daily combination. Increase dose if breakthrough bleeding occurs. Consider non-oral routes for women with triglycerides >500 mg/dL or gallstones. |
| Patient Advice | Take exactly as prescribed; do not skip doses. · Report abnormal vaginal bleeding, breast lumps, chest pain, shortness of breath, leg swelling, or jaundice immediately. · Do not use if pregnant, breastfeeding, or planning pregnancy. · Smoking increases risk of blood clots; avoid smoking. · May increase risk of stroke, heart attack, and breast cancer; discuss risks and benefits. · Premphase: First 14 days take only the estrogen tablet (blue), next 14 days take combination tablet (white). · Prempro: Take one tablet daily, same time each day. · Store at room temperature, protect from light and moisture. · Regular mammograms and pelvic exams are necessary. · If you miss a dose, take it as soon as remembered; if close to next dose, skip missed dose – do not double. |