The following information is taken from Premarin’s leaflet:


Three independent, case-controlled studies have reported an increased risk of endometrial cancer in postmenopausal women exposed to exogenous estrogens for more than one year. This risk was independent of the other known risk factors for endometrial cancer. These studies are further supported by the finding that incidence rates of endometrial cancer have increased sharply since 1969 in eight different areas of the United States with population-based cancer-reporting systems, an increase which may be related to the rapidly expanding use of estrogens during the last decade. The three case-controlled studies reported that the risk of endometrial cancer in estrogen users was about 4.5 to 13.9 times greater than in nonusers. The risk appears to depend on both duration of treatment and on estrogen dose. In view of these findings, when estrogens are used for the treatment of menopausal symptoms, the lowest dose that will control symptoms should be utilized and medication should be discontinued as soon as possible. When prolonged treatment is medically indicated, the patient should be reassessed, on at least a semiannual basis, to determine the need for continued therapy. Although the evidence must be considered preliminary, one study suggests that cyclic administration of low doses of estrogen may carry less risk than continuous administration. It therefore appears prudent to utilize such a regimen. Close clinical surveillance of all women taking estrogens is important. In all cases of undiagnosed persistent or recurring abnormal vaginal bleeding, adequate diagnostic measures should be undertaken to rule out malignancy. There is no evidence at present that “natural” estrogens are more or less hazardous than “synthetic” estrogens at equiestrogenic doses.

What You Should Know About Estrogens: Estrogens are female hormones produced by the ovaries. The ovaries make several different kinds of estrogens. In addition, scientists have been able to make a variety of synthetic estrogens. As far as we know, all these estrogens have similar properties and, therefore, much the same usefulness, side effects, and risks. This leaflet is intended to help you understand what estrogens are used for, the risks involved in their use, and how to use them as safely as possible. This leaflet includes the most important information about estrogens, but not all the information. If you want to know more, you should ask your doctor for more information, or you can ask your doctor or pharmacist to let you read the package insert prepared for the doctor.

Uses of Estrogen
THERE IS NO PROPER USE OF ESTROGENS IN A PREGNANT WOMAN. Estrogens are prescribed by doctors for a number of purposes, including: To provide estrogen during a period of adjustment when a woman’s ovaries stop producing a majority of her estrogens, in order to prevent certain uncomfortable symptoms of estrogen deficiency. (With the menopause, which generally occurs between the ages of 45 and 55, women produce a much smaller amount of estrogens.) To prevent symptoms of estrogen deficiency when a woman’s ovaries have been removed surgically before the natural menopause. To prevent pregnancy. (Estrogens are given along with a progestogen, another female hormone; these combinations are called oral contraceptives, or birth-control pills. Patient labeling is available to women taking oral contraceptives and they will not be discussed in this leaflet.) To treat certain cancers in women and men.

Estrogens in the Menopause
In the natural course of their lives, all women eventually experience a decrease in estrogen production. This usually occurs between ages 45 and 55, but may occur earlier or later. Sometimes the ovaries may need to be removed before natural menopause by an operation, producing a “surgical menopause. When the amount of estrogen in the blood begins to decrease, many women may develop typical symptoms: feelings of warmth in the face, neck, and chest, or sudden intense episodes of heat and sweating throughout the body (called “hot flashes” or “hot flushes”). These symptoms are sometimes very uncomfortable. Some women may also develop changes in the vagina (called “atrophic vaginitis”) that cause discomfort, especially during and after intercourse. Estrogens can be prescribed to treat these symptoms of the menopause. It is estimated that considerably more than half of all women undergoing the menopause have only mild symptoms or no symptoms at all and, therefore, do not need estrogens. Other women may need estrogens for a few months, while their bodies adjust to lower estrogen levels. Sometimes the need will be for periods longer than six months. In an attempt to avoid overstimulation of the uterus (womb), estrogens are usually given cyclically during each month of use, such as three weeks of pills followed by one week without pills. Sometimes women experience nervous symptoms or depression during menopause. There is no evidence that estrogens are effective for such symptoms without associated vasomotor symptoms. In the absence of vasomotor symptoms, estrogens should not be used to treat nervous symptoms, although other treatment may be needed. You may have heard that taking estrogens for long periods (years) after the menopause will keep your skin soft and supple and keep you feeling young. There is no evidence that this is so, however, and such long-term treatment carries important risks.

The Dangers of Estrogens
Endometrial cancer. There are reports that if estrogens are used in the postmenopausal period for more than a year, there is an increased risk of endometrial cancer (cancer of the lining of the uterus). Women taking estrogens have roughly 5- to 10-times as great a chance of getting this cancer as women who take no estrogens. To put this another way, while a postmenopausal woman not taking estrogens has 1 chance in 1,000 each year of getting endometrial cancer, a woman taking estrogens has 5 to 10 chances in 1,000 each year. For this reason it is important to take estrogens only when they are really needed. The risk of this cancer is greater the longer estrogens are used and when larger doses are taken. Therefore, you should not take more estrogen than your doctor prescribes. It is important to take the lowest dose of estrogen that will control symptoms and to take it only as long as it is needed. If estrogens are needed for longer periods of time, your doctor will want to reevaluate your need for estrogens at least every six months. Women using estrogens should report any vaginal bleeding to their doctors; such bleeding may be of no importance, but it can be an early warning of endometrial cancer. If you have undiagnosed vaginal bleeding, you should not use estrogens until a diagnosis is made and you are certain there is no endometrial cancer. Note: If you have had your uterus removed (total hysterectomy), there is no danger of developing endometrial cancer. Other possible cancers. Estrogens can cause development of other tumors in animals, such as tumors of the breast, cervix, vagina, or liver, when given for a long time. At present there is no good evidence that women using estrogens in the menopause have an increased risk of such tumors, but there is no way yet to be sure they do not; and one study raises the possibility that use of estrogens in the menopause may increase the risk of breast cancer many years later. This is a further reason to use estrogens only when clearly needed. While you are taking estrogens, it is important that you go to your doctor at least once a year for a physical examination. Also, if members of your family have had breast cancers, or if you have breast nodules, or abnormal mammograms (breast X rays), your doctor may wish to carry out more frequent examinations of your breasts. Gallbladder disease. Women who use estrogens after menopause are more likely to develop gallbladder disease needing surgery than women who do not use estrogens. Birth-control pills have a similar effect. Abnormal blood clotting. Taking estrogens may increase the risk of blood clotting in various parts of the body. This can result in a stroke (if the clot is in the brain), a heart attack (a clot in a blood vessel of the heart), or a pulmonary embolus (a clot which forms in the legs or pelvis, then breaks off and travels to the lungs). Any of these can be fatal. It is recommended that if you have had clotting in the legs or lungs, or a heart attack or stroke, while you were using estrogens or birth-control pills, you should not use estrogens (unless they are being used to treat cancer of the breast or prostate). If you have had a stroke or heart attack, or if you have angina pectoris, estrogens should be used with great caution and only if clearly needed (for example, if you have severe symptoms of the menopause). Inflammation of the pancreas (Pancreatitis). Women with high triglyceride levels may have an increased risk of developing inflammation of the pancreas.

Special Warning About Pregnancy
You should not receive estrogen if you are pregnant. If this should occur, there is a greater than usual chance that the developing child will be born with a birth defect, although the possibility remains fairly small. A female child may have an increased risk of developing cancer of the vagina or cervix later in life (in the teens or twenties). Every possible effort should be made to avoid exposure to estrogens during pregnancy. If exposure occurs, see your doctor.

Other Effects of Estrogens
In addition to the serious known risks of estrogens described above, estrogens have the following side effects and potential risks: Nausea and vomiting. The most common side effect of estrogen therapy is nausea. Vomiting is less common. Effects on breasts. Estrogens may cause breast tenderness or enlargement and may cause the breasts to secrete a liquid. These effects are not dangerous. Effects on the uterus. Estrogens may cause benign fibroid tumors of the uterus to get larger. Effects on liver. Women taking oral contraceptives develop, on rare occasions, a tumor of the liver which can rupture and bleed into the abdomen and may cause death. So far, these tumors have not been reported in women using estrogens in the menopause, but you should report any swelling or unusual pain or tenderness in the abdomen to your doctor immediately. Women with a past history of jaundice (yellowing of the skin and white parts of the eyes) may get jaundice again during estrogen use. If this occurs, stop taking estrogens and see your doctor. Other effects. Estrogens may cause excess fluid to be retained in the body. This may make some conditions worse, such as asthma, epilepsy, migraine, heart disease, or kidney disease.

Estrogens have important uses, but they have serious risks as well. You must decide, with your doctor, whether the risks are acceptable to you in view of the benefits of treatment. Except where your doctor has prescribed estrogens for use in special cases of cancer of the breast or prostate, you should not use estrogens if you have cancer of the breast or uterus, are pregnant, have undiagnosed abnormal vaginal bleeding, clotting in the legs or lungs, or have had a stroke, heart attack or angina, or clotting in the legs or lungs in the past while you were taking estrogens. You can use estrogens as safely as possible by understanding that your doctor will require regular physical examinations while you are taking them, will try to discontinue the drug as soon as possible, and use the smallest dose possible. Be alert for signs of trouble including: Abnormal bleeding from the vagina. Pains in the calves or chest, or sudden shortness of breath, or coughing blood. Severe headache, dizziness, faintness, or changes in vision. Breast lumps (you should ask your doctor how to examine your own breasts). Jaundice (yellowing of the skin). Mental depression.

Your doctor has prescribed this drug for you and you alone. Do not give the drug to anyone else.


  • Premarin® (conjugated estrogens tablets, USP) tablets for oral administration.
  • Premarin® Vaginal Cream — Premarin® in a nonliquefying base, designed for vaginal use.
  • Premarin® Intravenous — Premarin® specially prepared for intravenous and intramuscular use.
  • Manufactured by:
    Ayerst Laboratories Inc.
    A Wyeth-Ayerst Company
    Philadelphia, PA 19101
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