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Is premarin estrogen?

Yes. Premarin is a form of estrogen therapy derived from conjugated estrogens in pregnant mare urine. It contains at least 10 estrogens, including estrone (50–60%), equilin (22.5–32.5%), and estradiol (<5%).

It relieves symptoms of low estrogen, such as hot flashes, vaginal dryness, and atrophy, and is used to prevent osteoporosis and treat advanced breast or prostate cancer pain.

Common side effects

  • Abdominal pain and bloating
  • Breast tenderness, pain, or enlargement
  • Lack of energy and mood changes
  • Nausea
  • Back or leg pain not due to clot
  • Fluid retention
  • Headache and vision changes
  • Vaginal discharge or yeast infection
  • Hair loss

Serious side effects

  • Heart attack and stroke
  • Blood clots (DVT or pulmonary embolism)
  • Increased risk of dementia
  • Breast, ovarian, and endometrial cancer
  • Gallbladder and liver disease
  • High blood pressure and blood sugar
  • Uterine fibroids
  • Severe allergic reactions

Who should avoid Premarin?

Do not use if you have:

  • Unusual vaginal bleeding
  • Breast, endometrial, or estrogen‑dependent cancer
  • History of heart attack, stroke, or blood clots
  • Liver disease or bleeding disorders
  • Allergy to any ingredient
  • Pregnancy or planning pregnancy

FDA Boxed Warning

  • Estrogen‑alone increases endometrial cancer risk
  • Not for preventing heart disease or dementia
  • Combined with progestin, may increase risks of dementia, stroke, heart attack, blood clots, and breast cancer

Important considerations

  • Inform your provider about thyroid, liver, kidney, heart conditions, migraines, seizures, and eye issues
  • Undergo regular exams: blood pressure, breast/mammogram, pelvic exam, and Pap smear
  • Discuss all prescription and OTC medications, vitamins, and supplements to avoid interactions

How Premarin differs

Premarin is animal‑derived, whereas other estrogens are synthetic or bioidentical. Uses and FDA approvals may vary.

Benefits of Premarin

  • Relieves menopausal vaginal symptoms: dryness, itching, painful intercourse
  • Alleviates hot flashes and night sweats
  • Helps prevent postmenopausal osteoporosis

Sources

  • Premarin (conjugated estrogens) Tablets, USP. Pfizer. Last updated 02/2024. Accessed Jan 23, 2025.
  • Vance DA. Premarin: history of a controversial drug. Int J Pharm Compd. 2007;11(4):282‑286. Accessed Jan 23, 2025.