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A mixture of a variety of estrogens obtained entirely from natural sources, usually from the urine of a pregnant mare. These estrogens are blended to represent the average composition of the hormonal materials.

They usually contain estrone, equilin, and 17 a-dihydroequilin, and smaller amounts of 17 a-estradiol, equilenin, and 17 a-dihydroequilenin

The most well-known and most common of pharmaceuticals containing conjugated estrogens is Premarin.

There are synthetic, FDA-approved alternatives. such as Ogen, Estrace, Estradiol Transdermal System, Estradiol tablets, Estropipate, Estrone, Meneste, and Cenestin.


Dosage varies widely with the reason for taking the drug. 1.25 mg is most common for post-menopausal women, with dosage adjusted based on the patient's reaction to the medication. For less common medical problems, dosage may run up to 7.5mg daily.

A physical examination is recommended before a patient starts taking conjugated estrogens, and also regular examinations while the drugs are being taken.

Side Effects:

Changes in vaginal bleeding pattern and abnormal withdrawal bleeding or flow, Breakthrough bleeding, spotting, increase in size of uterine fibromyomata. vaginal candidiasis, changes in amount of cervical secretion, breast tenderness or enlargement, nausea, vomiting, abdominal cramps, bloating, skin chloasma or melasma, loss of scalp hair, intolerance of contact lenses, headache, migraine, dizziness, depression, increases or decreases in weight, reduced tolerance to carbohydrates, changes in libido

RxLine - http://www.rxline.com

Pharmacologic class

Brand Names
Hormone replacement therapy - (see brand name writeup for details)
Conjugated estrogens derived from animal sources have the same effect as natural endogenous hormones in the body, stimulating estrogen receptor-containing cells, particularly in the female reproductive system, breasts, and secondary gender specific characteristics.
Pregnancy (Category X), breast cancer, clotting disorders, undiagnosed vaginal bleeding
A progesterone should be used with estrogens unless the uterus has been removed. Caution should be used if the patient has liver or gallbladder disease, also with some diseases of the bone associated with high calcium. Not recommended for teenagers and nursing mothers.
No common interactions known
Adverse Reactions
Increased risk of estrogen-dependent cancers, gallstones, blood clots, liver tumors, nausea, uterine bleeding, edema, weight gain, sore breasts, high blood pressure, depression, and intolerance to contact lenses.
Additional Information

Patients taking estrogens should have both an initial complete physical and repeat annual physicals including blood pressure, mammograms, and a PAP smear. Stop the medicine if jaundice or high blood pressure occurs or if immobilized or for at least two weeks before any surgery associated with thromboembolism.

Current studies released in July of 2002 recommend not taking estrogen / progesterone combinations for prevention of heart disease and stroke, or to lower cholesterol levels. The relative risk of morbidity and mortality is actually increased in patients taking these medications rather than descreased. Taking estrogens for relief of symptoms of menopause or for other reasons listed above is still a reasonable course of action, and should be discussed with your doctor.

Date of most recent Update
August 5, 2002
Further information is available in the writeup for the brand name(s) of this medication - Thanks to Saige for the initial writeup!

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