Other important side effects include:
- gallstones, and the gallstones may result in abdominal pain and require surgery.
- Migraine headaches, and
- retention of water (edema).
Melasma--tan or brown patches-- may develop on the forehead, cheeks, or temples. These may persist even after the estrogen is stopped.
Blood clots are an occasional, serious side effect of estrogen therapy and are dose-related. (The higher the dose of estrogen, the greater the risk of blood clots.) Cigarette smokers are at a higher risk than non-smokers for blood clots, and patients requiring estrogens should be encouraged to quit smoking.
Estrogens can promote thickening of the lining of the uterus (endometrial hyperplasia) and increase the risk of uterine cancer. At diagnosis, endometrial cancers in recipients of estrogens are generally at an earlier stage and are less aggressive when they are discovered. Survival from endometrial cancer also is better in women taking estrogens than in those not taking estrogens. The addition of a progestin to estrogen therapy offsets the risk of endometrial cancer. Conflicting data exists on the association between estrogens and breast cancer. There may be a small increase in risk. The effect of concomitant progestin therapy on the risk of estrogen-induced breast cancer is unclear. Conjugated estrogens are well-absorbed from the vagina and into the blood. The amount absorbed depends on the frequency of use and the amount used. Thus, more frequent use or larger amounts of vaginal estrogens can have effects throughout the body (see conjugated estrogens, Premarin). The Women's Health Initiative found that postmenopausal women (50-79 years old) taking conjugated estrogens had an increased risk of breast cancer, blood clots, and stroke. There was also an increased risk of impaired cognition and/or dementia among women over age 65.
Quick GuideMenopause & Perimenopause: Symptoms, Signs
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Need help identifying pills and medications?
Use the pill identifier tool on RxList.