Conjugated Estrogens

Reviewed on 3/25/2022

What Are Conjugated Estrogens and How Does They Work?

Conjugated Estrogens is a prescription medication used to treat symptoms of menopausal vasomotor, female hypogonadism, osteoporosis, prostate cancer, abnormal uterine bleeding, breast cancer, and primary ovarian failure.

  • Conjugated Estrogens are available under the following different brand names: Premarin

What Are Dosages of Conjugated Estrogens?

Adult dosage


  • 0.3mg
  • 0.45mg
  • 0.625mg
  • 0.9mg
  • 1.25mg

Powder for injection

  • 25mg

Menopausal Vasomotor Symptoms, Atrophic Vaginitis/Kraurosis Vulvae

Adult dosage

  • 0.3 mg orally once daily in either continuous daily regimen or cyclic regimen (25 days on, 5 days off); adjusted as needed; use the lowest dose that controls symptoms; may be given daily if medical assessment warrants it

Female Hypogonadism

Adult dosage

  • 0.3-0.625 mg orally once daily in the cyclic regimen (3 weeks on, 1 week off); maybe titrated every 6-12 months; adjusted as needed; add progestin treatment should be added to maintain bone mineral density once skeletal maturity achieved



Adult dosage

  • 0.3 mg orally once daily in the cyclic regimen (25 days on, 5 days off); adjusted as needed based on clinical response; may be given daily if medical assessment warrants it; administer the lowest effective dose
  • May also be used in combination with medroxyprogesterone acetate

Prostate Cancer

Palliation only

Adult dosage

  • 1.25-2.5 mg orally every 8 hours

Abnormal Uterine Bleeding

Adult dosage

  • 25 mg IV/IM; repeated in 6-12 hours or as needed or 25 mg IV repeated every 4 hours for 24 hr; if no response after 2 doses, re-evaluate therapy
  • Alternative regimen: 10-20 mg/day orally divided every 4 hours
  • May administer low dose medroxyprogesterone acetate with therapy or the following therapy
  • Cyclic therapy: 25 days on, 5 days off; either 3 weeks on, 1 week off

Female Castration/Primary Ovarian Failure

Adult dosage

  • 1.25 mg orally once daily in the cyclic regimen (25 days on, 5 days off); adjusted as needed; administer the lowest effective dose

Breast Cancer Palliation

Adult dosage

  • Metastatic disease in selected patients (males and females):10 mg orally every 8 hours for more than 3 months

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”

What Are Side Effects Associated with Using Conjugated Estrogens?

Common side effects of Conjugated Estrogens include:

  • nausea,
  • gas,
  • stomach pain,
  • headache,
  • back pain,
  • depression,
  • sleep problems (insomnia),
  • breast pain,
  • vaginal itching or discharge,
  • changes in the menstrual periods, and
  • breakthrough bleeding.

Serious side effects of Conjugated Estrogens include:

  • chest pain or pressure,
  • pain spreading to the jaw or shoulder,
  • nausea,
  • sweating,
  • sudden numbness or weakness (especially on one side of the body),
  • sudden severe headache,
  • slurred speech,
  • problems with vision or balance,
  • sudden vision loss,
  • stabbing chest pain,
  • feeling short of breath,
  • coughing up blood,
  • pain or warmth in one or both legs,
  • swelling or tenderness in the stomach,
  • yellowing of the skin or eyes (jaundice),
  • memory problems,
  • confusion,
  • unusual behavior,
  • unusual vaginal bleeding,
  • pelvic pain,
  • lump in your breast,
  • vomiting,
  • constipation,
  • increased thirst or urination,
  • muscle weakness,
  • bone pain, and
  • lack of energy

Rare side effects of Conjugated Estrogens include:

  • none 

This is not a complete list of side effects and other serious side effects or health problems that may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Conjugated Estrogens?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Conjugated Estrogens have severe interactions with the following drug:
  • Conjugated Estrogens have serious interactions with at least 39 other drugs.
  • Conjugated Estrogens have moderate interactions with at least 160 other drugs.
  • Conjugated Estrogens have minor interactions with at least 35 other drugs.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns.

What Are Warnings and Precautions for Conjugated Estrogens?


Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Conjugated Estrogens?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Conjugated Estrogens?”


  • Use caution in diabetes mellitus, hyperlipidemias, hypertension, hypothyroidism, advanced age, hepatic or renal impairment, uterine leiomyomata, porphyria, patients with defects of lipoprotein metabolism, hypertriglyceridemia, ovarian cancer, systemic lupus erythematosus, exacerbation of endometriosis or other conditions, smoking, diseases exacerbated by fluid retention
  • Manage appropriately risk factors for arterial vascular disease (e.g., hypertension, diabetes mellitus, tobacco use, hypercholesterolemia, and obesity) and/or venous thromboembolism (e.g., personal history or family history of VTE, obesity, and systemic lupus erythematosus)
  • In patients with pre-existing hypertriglyceridemia, estrogen therapy may be associated with elevations of plasma triglycerides leading to pancreatitis and other complications
  • Estrogens may be poorly metabolized in patients with impaired liver function; exercise caution in patients with a history of cholestatic jaundice associated with past estrogen use or with pregnancy; in the case of recurrence, discontinue medication
  • Patients dependent on thyroid hormone replacement therapy who are also receiving Estrogens may require increased doses of thyroid replacement therapy; these patients should have their thyroid function monitored to maintain their free thyroid hormone levels in an acceptable range
  • A 2 to 4-fold increase in the risk of gallbladder disease requiring surgery in postmenopausal women receiving Estrogens reported
  • Retinal vascular thrombosis reported in patients receiving Estrogens; discontinue medication pending examination if there is a sudden partial or complete loss of vision, or a sudden onset of proptosis, diplopia, or migraine; if examination reveals papilledema or retinal vascular lesions, Estrogens should be discontinued
  • There are, possible risks that may be associated with the use of progestins with Estrogens compared to estrogen-alone regimens, including a possible increased risk of breast cancer, adverse effects on lipoprotein metabolism (e.g., lowering HDL, raising LDL), and impairment of glucose tolerance
  • Discontinue if any of the following develop: Jaundice, signs of venous thromboembolism, visual problems (may cause contact lens intolerance), massive blood pressure increase, major surgery or prolonged immobilization occurring in 4 weeks, new migraine, depression
  • Women with protein C or S deficiency (inherited thrombophilia), may have an increased risk of venous thromboembolism
  • Do not use with conditions that predispose to hyperkalemia
  • Conditions exacerbated by fluid retention (asthma, epilepsy, migraines, cardiac or renal dysfunction)
  • Risk of hypercalcemia in patients with breast cancer and bone metastases
  • Increased risk of ovarian and endometrial cancer reported in women who used hormonal therapy for menopausal symptoms
  • Long-term postmenopausal estrogen treatment has been associated with an increased risk of breast cancer, MI, stroke, DVT/PE, and dementia
  • Patients on warfarin or other oral anticoagulants: Estrogens increase thromboembolic risk; an increase in anticoagulant dosage may be warranted
  • Discontinue therapy if pancreatitis occurs; estrogen compounds generally associated with increased triglyceride levels
  • Cases of anaphylaxis and angioedema have been reported; exogenous Estrogens may exacerbate symptoms of angioedema in women with hereditary angioedema
  • Use caution in individuals with severe hypocalcemia

Pregnancy and Lactation

  • Do not use it in pregnancy. The risks involved outweigh the potential benefits. Safer alternatives exist.
  • Lactation
    • Use controversial; Estrogens are excreted into breast milk in small quantities; use with caution
Medscape. Conjugated Estrogens.

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