Last reviewed 2026-04-20 · How we verify

Premarin (Conjugated estrogens)

At a glance

Approved indications

• Dyspareunia
• Menopausal flushing

Boxed warnings

• WARNING: ENDOMETRIAL CANCER, CARDIOVASCULAR DISORDERS, BREAST CANCER and PROBABLE DEMENTIA Estrogen-Alone Therapy Endometrial Cancer There is an increased risk of endometrial cancer in a woman with a uterus who uses unopposed estrogens. Adding a progestin to estrogen therapy has been shown to reduce the risk of endometrial hyperplasia, which may be a precursor to endometrial cancer. Adequate diagnostic measures, including directed or random endometrial sampling when indicated, should be undertaken to rule out malignancy in postmenopausal women with undiagnosed persistent or recurring abnormal genital bleeding. (See WARNINGS, Malignant Neoplasms, Endometrial cancer .) Cardiovascular Disorders and Probable Dementia Estrogen-alone therapy should not be used for the prevention of cardiovascular disease or dementia. (See CLINICAL STUDIES and WARNINGS, Cardiovascular Disorders and Probable Dementia .) The Women's Health Initiative (WHI) estrogen-alone substudy reported increased risks of stroke and deep vein thrombosis (DVT) in postmenopausal women (50 to 79 years of age) during 7.1 years of treatment with daily oral conjugated estrogens (CE) [0.625 mg]-alone, relative to placebo. (See CLINICAL STUDIES and WARNINGS, Cardiovascular disorders .) The WHI Memory Study (WHIMS) estrogen-alone ancillary study of the WHI reported an increased risk of developing probable dementia in postmenopausal women 65 years of age or older during 5.2 years of treatment with daily CE (0.625 mg)-alone, relative to placebo. It is unknown whether this finding applies to younger postmenopausal women. (See CLINICAL STUDIES and WARNINGS, Probable Dementia and PRECAUTIONS, Geriatric Use .) In the absence of comparable data, these risks should be assumed to be similar for other doses of CE and other dosage forms of estrogens. Estrogens with or without progestins should be prescribed at the lowest effective doses and for the shortest duration consistent with treatment goals and risks for the individual woman. Estrogen Plus Progestin Therapy Cardiovascular Disorders and Probable Dementia Estrogen plus progestin therapy should not be used for the prevention of cardiovascular disease or dementia. (See CLINICAL STUDIES and WARNINGS, Cardiovascular disorders and Probable Dementia .) The WHI estrogen plus progestin substudy reported increased risks of DVT, pulmonary embolism (PE), stroke and myocardial infarction (MI) in postmenopausal women (50 to 79 years of age) during 5.6 years of treatment with daily oral CE (0.625 mg) combined with medroxyprogesterone acetate (MPA) [2.5 mg], relative to placebo. (See CLINICAL STUDIES and WARNINGS, Cardiovascular disorders .) The WHIMS estrogen plus progestin ancillary study of the WHI reported an increased risk of developing probable dementia in postmenopausal women 65 years of age or older during 4 years of treatment with daily CE (0.625 mg) combined with MPA (2.5 mg), relative to placebo. It is unknown whether this finding applies to younger postmenopausal women. (See CLINICAL STUDIES and WARNINGS, Probable Dementia and PRECAUTIONS, Geriatric Use .) Breast Cancer The WHI estrogen plus progestin substudy also demonstrated an increased risk of invasive breast cancer. (See CLINICAL STUDIES and WARNINGS, Malignant Neoplasms, Breast cancer .) In the absence of comparable data, these risks should be assumed to be similar for other doses of CE and MPA, and other combinations and dosage forms of estrogens and progestins. Estrogens with or without progestins should be prescribed at the lowest effective doses and for the shortest duration consistent with treatment goals and risks for the individual woman.

Common side effects

• Deep and superficial venous thrombosis
• Pulmonary embolism
• Thrombophlebitis
• Myocardial infarction
• Stroke
• Increase in blood pressure
• Breast cancer
• Endometrial cancer
• Ovarian cancer
• Endometrial hyperplasia
• Pancreatitis
• Ischemic colitis

Key clinical trials

• Trial of 225Ac-DOTATATE (RYZ101) in Subjects With ER+, HER2-negative Unresectable or Metastatic Breast Cancer Expressing SSTRs. (PHASE1,PHASE2)
• A Study of Single Dose of BL0175 in Postmenopausal Women (PHASE1)
• Patritumab Deruxtecan (U3-1402) in Unresectable Locally Advanced or Metastatic Breast Cancer (PHASE2)
• ERADICATE: A Phase Ib/II Study of Elacestrant Plus Trastuzumab Deruxtecan in Patients With CDK4/6 Inhibitor and Endocrine-resistant HR+/HER2-low or HER2-ultralow Metastatic Breast Cancer (PHASE1,PHASE2)
• Pilot Study of Bazedoxifene Plus Conjugated Estrogen on Imaging and Blood Biomarkers (EARLY_PHASE1)
• Phase IIB Trial of Bazedoxifene Plus Conjugated Estrogens (PHASE2)
• A Clinical Study of SYS6023 in Patients With Advanced Solid Tumors (PHASE1)
• DATO-BASE: DATOpotamab-deruxtecan for Breast Cancer Brain metAstaSEs (PHASE2)

Patents

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Premarin CI brief — competitive landscape report
• Premarin updates RSS · CI watch RSS
• Pfizer portfolio CI