What is esterified estrogens, and how does it work (mechanism of action)?

Esterified estrogens are a mixture of several estrogens, a type of female hormone. Estrogens cause growth and development of female sex organs and the maintenance of sex characteristics, including growth of underarm and pubic hair and shaping of body contours and skeleton. Estrogens also increase secretions from the cervix and promote growth of the inner lining of the uterus (endometrium).

What brand names are available for esterified estrogens?

Estratab (Discontinued in the USA), Menest

Is esterified estrogens available as a generic drug?


Do I need a prescription for esterified estrogens?


What are the side effects of esterified estrogens?

The most common endocrine side effects are

  • breakthrough
  • bleeding or spotting,
  • loss of periods, or
  • excessively prolonged periods,
  • breast pain,
  • breast enlargement, and
  • changes in sexuality (increase or decrease in libido).

Other important side effects include:

Melasma (tan or brown patches) may develop on the forehead, cheeks, or temples. These may persist even after the estrogen is stopped. Estrogens may cause an increase in the curvature of the cornea, and, therefore, patients with contact lenses may develop intolerance to their lenses.

What is the dosage for esterified estrogens?

The dose for menopause and related conditions is 0.3 to 1.25 mg daily for 3 weeks then 1 week off. Female hypogonadism is treated with 2.5 to 7.5 mg daily for 20 days then 10 days off. Breast cancer is treated with 10 mg three times daily for at least 3 months and the dose for prostate cancer is 1.25 to 2.5 mg 3 times daily.

Which drugs or supplements interact with esterified estrogens?

Estrogens increase the liver‘s ability to manufacture proteins that are required for blood to clot. Therefore, patients receiving warfarin (Coumadin), which reduces clotting (“thins” the blood) by inhibiting the production of proteins required for clotting, should receive clotting tests if an estrogen is added to their treatment. If blood clots too easily, the dose of warfarin may need to be increased.

Rifampin, barbiturates, carbamazepine (Tegretol), griseofulvin, phenytoin (Dilantin) and primidone can increase the elimination of estrogen by enhancing the liver’s ability to metabolize (destroy) it. Use of these drugs may result in a reduction of the beneficial effects of estrogens. Conversely, drugs such as erythromycin, ketoconazole (Nizoral), itraconazole (Sporanox), and ritonavir (Norvir) may reduce the elimination of estrogens by the liver and lead to increased levels of estrogens in the blood. Grapefruit juice also may increase levels of estrogen by increasing the absorption of estrogens from the intestine. Increased levels of estrogens in the blood may result in more estrogen-related side effects.

Is esterified estrogens safe to take if I’m pregnant or breastfeeding?

Estrogens should not be used during pregnancy because of an increased risk of fetal abnormalities.

Estrogens are secreted in milk and cause unpredictable effects in the infant. Therefore, they generally should not be used during breastfeeding.

What else should I know about esterified estrogens?

What preparations of esterified estrogens are available?

Tablets: 0.3, 0.625, 1.25, and 2.5 mg.

How should I keep esterified estrogens stored?

Tablets should be stored between 2 C (36 F) and 30 C (86 F).

Menopause & Perimenopause: Symptoms, Signs

Medically Reviewed on 12/17/2018


Medically reviewed by John P. Cunha, DO, FACOEP; Board Certified Emergency Medicine

Reference: FDA Prescribing Information