PREMPHASE 14/14
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PREMPHASE 14/14 (PREMPHASE 14/14).
Conjugated estrogens (CE) bind to estrogen receptors (ERα and ERβ), modulating gene transcription and non-genomic signaling pathways to induce estrogenic effects. Medroxyprogesterone acetate (MPA) is a progestin that binds to progesterone receptors, suppressing endometrial proliferation and counteracting estrogen-induced endometrial hyperplasia. The combination provides hormone replacement therapy with reduced risk of endometrial cancer.
| Metabolism | Conjugated estrogens are primarily metabolized in the liver via cytochrome P450 3A4 (CYP3A4) and other CYP enzymes, with conjugation (glucuronidation and sulfation) to inactive metabolites. Medroxyprogesterone acetate is extensively metabolized in the liver, primarily via hydroxylation and conjugation, with CYP3A4 playing a major role. Both undergo enterohepatic recirculation and are excreted in urine and feces. |
| Excretion | Conjugated estrogens are excreted primarily in urine (≥90%) as glucuronide and sulfate conjugates; medroxyprogesterone acetate is extensively metabolized and excreted in urine (≤60%) and feces (≤30%) as metabolites. |
| Half-life | Conjugated estrogens have a terminal elimination half-life of 12-24 hours for conjugated equine estrogens; medroxyprogesterone acetate has a half-life of 12-17 hours. Steady-state is reached within 5-7 days. |
| Protein binding | Conjugated estrogens: ~50-80% bound to albumin and sex hormone-binding globulin (SHBG); medroxyprogesterone acetate: ~85-90% bound to albumin (not SHBG). |
| Volume of Distribution | Conjugated estrogens: Vd ~1-2 L/kg, distributed widely into tissues including breast, uterine, and adipose tissue; medroxyprogesterone acetate: Vd ~0.5-1 L/kg. |
| Bioavailability | Oral bioavailability of conjugated estrogens is 60-80%; medroxyprogesterone acetate is 100% (oral). Transdermal or vaginal routes for estrogens alone show 10-20% absorption vs oral. |
| Onset of Action | Oral: Onset of estrogenic effects (e.g., relief of vasomotor symptoms) within 2-4 weeks; progestogenic effects on endometrium occur after 10-14 days of continuous dosing. |
| Duration of Action | Extended duration: For vasomotor symptoms, continuous daily dosing required; for endometrial protection, 14 days of progestin per cycle (cyclic regimen). Clinical effects persist for 24-48 hours after last dose. |
| Molecular Weight | Conjugated estrogens: average ~280 Da (variable); medroxyprogesterone acetate: 386.53 Da |
One tablet orally once daily, each tablet contains conjugated estrogens 0.625 mg and medroxyprogesterone acetate 5 mg.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment recommended; use with caution in patients with renal impairment. |
| Liver impairment | Contraindicated in patients with severe hepatic disease (Child-Pugh class C); use with caution in mild to moderate impairment (Child-Pugh class A or B) with dose reduction as clinically indicated. |
| Pediatric use | Not indicated for use in pediatric patients. |
| Geriatric use | No specific dose adjustment; monitor for adverse effects such as thromboembolic events and malignancy. |
| 1st trimester | Estrogens are contraindicated in pregnancy; use in the first trimester may cause fetal harm. Conjugated estrogens (0.625 mg) and medroxyprogesterone acetate (5 mg) are not indicated for use during pregnancy. |
| 2nd trimester | Contraindicated; estrogens may cause fetal genital anomalies and other adverse effects. Avoid use in second trimester. |
| 3rd trimester | Contraindicated; estrogens may delay or arrest fetal development and cause other toxicities. Do not use. |
Clinical note
Comprehensive clinical and safety monograph for PREMPHASE 14/14 (PREMPHASE 14/14).
| Placental transfer | Estrogens and progestins readily cross the placenta. Conjugated estrogens and medroxyprogesterone acetate have documented placental transfer. |
| Breastfeeding | Estrogens and progestins are excreted in breast milk. Use during breastfeeding may reduce milk production and quality. Avoid use in nursing mothers; consider alternative therapy. |
■ FDA Black Box Warning
Estrogen-plus-progestin therapy should not be used for the prevention of cardiovascular disease. The Women's Health Initiative (WHI) study reported increased risks of myocardial infarction, stroke, invasive breast cancer, pulmonary emboli, and deep vein thrombosis in postmenopausal women (50-79 years) treated with daily oral CE 0.625 mg/MPA 2.5 mg. Risks are dose- and duration-dependent.
| Serious Effects |
PregnancyUndiagnosed abnormal genital bleedingKnown or suspected breast cancer (except in select cases)Known or suspected estrogen-dependent neoplasiaActive or past history of venous thromboembolism (DVT, PE)Active or past arterial thromboembolic disease (e.g., stroke, MI)Known protein C, protein S, or antithrombin deficiency or other thrombophilic disordersKnown liver impairment or diseaseHypersensitivity to any component of PREMPHASE
| Precautions | Cardiovascular disorders: Increased risk of stroke and DVT; discontinue if thrombosis suspected., Malignancy: Increased risk of breast cancer (especially with combined therapy), endometrial cancer (estrogen-alone therapy), and ovarian cancer; perform regular breast exams and mammography., Dementia: Possible increased risk in women ≥65 years; avoid use for prevention., Gallbladder disease: Increased risk requiring cholecystectomy., Hypercalcemia: May occur in women with breast cancer and bone metastases., Visual abnormalities: Discontinue if sudden partial or complete vision loss occurs (consider retinal vascular thrombosis)., Fluid retention: Use with caution in conditions exacerbated by fluid retention (e.g., cardiac/renal dysfunction)., Hypothyroidism: May increase thyroid-binding globulin levels, requiring dose adjustment of thyroid hormone., Triglyceride elevations: Use with caution in patients with hypertriglyceridemia; monitor levels. |
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| Lactation Rating | L5 - Contraindicated |
| Teratogenic Risk | PREMARIN (conjugated estrogens) and medroxyprogesterone acetate (MPA) are contraindicated in pregnancy. Estrogen use during first trimester is associated with urogenital tract abnormalities (e.g., hypospadias) and possible transgenerational effects. Second and third trimester exposure may increase risk of fetal reproductive tract abnormalities (e.g., vaginal adenosis, clear cell adenocarcinoma) from DES-like effects, though risk is lower with current formulations. MPA is a progestin with potential androgenic effects; animal studies show feminization of male fetuses and masculinization of female fetuses at high doses. Overall, use in pregnancy is contraindicated. |
| Fetal Monitoring | Maternal: Blood pressure, liver function, glucose tolerance, thyroid function, serum lipid profile, and endometrial assessment (if uterus intact). Fetal: Not indicated as drug is contraindicated in pregnancy; if inadvertent exposure occurs, monitor for urogenital anomalies and developmental outcomes. |
| Fertility Effects | Estrogen-progestin combinations suppress ovulation and may impair fertility during use. After discontinuation, fertility typically returns, but prolonged use may delay return of ovulatory cycles. Endometrial changes from progestin component can affect implantation. No evidence of permanent fertility impairment. |
| Food/Dietary | No specific food interactions are documented. However, grapefruit juice may theoretically increase estrogen levels by inhibiting CYP3A4; consider moderate intake. Maintain adequate calcium and vitamin D intake for bone health. Avoid alcohol in excess as it may exacerbate menopausal symptoms and increase osteoporosis risk. |
| Clinical Pearls | Premphase 14/14 (conjugated estrogens 0.625 mg/medroxyprogesterone acetate 5 mg) is a continuous-sequential hormone therapy regimen: estrogen daily, with progestin added on days 15–28 of a 28-day cycle. Use only in women with an intact uterus. Avoid in women with known or suspected pregnancy, undiagnosed abnormal genital bleeding, breast cancer, estrogen-dependent neoplasia, active DVT/PE, or history of thrombophlebitis. Initiate at the lowest effective dose for the shortest duration. Monitor for endometrial hyperplasia, breast tenderness, and thromboembolic events. Consider alternative therapies for menopausal symptoms if cardiovascular or breast cancer risk is high. The progestin component reduces the risk of endometrial cancer associated with unopposed estrogen. |
| Patient Advice | Take one tablet daily at the same time each day. The regimen is 14 days of estrogen-only tablets (maroon) followed by 14 days of combination estrogen-progestin tablets (light blue). · Report any unusual vaginal bleeding, breast lumps, or signs of thrombosis (sudden chest pain, shortness of breath, leg swelling/pain) immediately. · Do not smoke while taking this medication; smoking increases the risk of blood clots and stroke. · Inform your healthcare provider about all medications you take, including herbal supplements, as some may interact. · Serious risks include endometrial cancer, cardiovascular events (heart attack, stroke, DVT/PE), and breast cancer. Discuss individual risks vs. benefits with your doctor. · This medication is not for use during pregnancy or breastfeeding. · If you miss a dose, take it as soon as remembered; if near next dose, skip the missed dose. Do not double dose. · Store at room temperature away from moisture and heat. |