Physicians prescribe the generically named drug tamoxifen as an agent to help fight breast cancer, Drugs.com reports. The medication prevents the female hormone estrogen from being as active as normal, which helps slow the growth of tumors. Tumors in the breasts and elsewhere typically grow with the help of estrogen, so decreasing the hormone's levels can fight the cancer. Doctors and gynecologists also may prescribe this drug, the Mayo Clinic states, in the prevention of breast cancer for those at high risk of getting it. Only rare serious side effects have been reported with the use of tamoxifen.
Menstrual Changes
Tamoxifen may alter a woman's menstrual cycle because hormones control this process. Without the regular level of estrogen in a woman's body, she may experience changes in menstruation, such as a cessation of periods--called by the medical term amenorrhea--occasionally missed periods and periods that become irregular, the Mayo Clinic reports. Drugs.com states the woman also may experience a discharge from her vagina during the initial stages of using tamoxifen. Common mild side effects such as these generally do not require medical help unless they continue or feel severe.
Pain and Swelling
Using tamoxifen also may induce pain in several areas of the body of the person using it. She may, for example, experience pain in her bones. She also may feel pain in the muscles of her body when she initiates use of tamoxifen, Drugs.com reports. The Mayo Clinic also lists swelling, particularly in the legs, feet, hands and fingers as common, non-serious side effects of tamoxifen that typically end after treatment begins.
Breathing Difficulties
At first, a woman taking tamoxifen may make a rattling noise when she breathes, the Mayo Clinic reports. She also may find it difficult to breathe normally even at rest for a day or two after her first treatment with tamoxifen. Although these problems may induce anxiety and panic, they generally disappear without the aid of a doctor, the Mayo Clinic states.
Weight Changes
Tamoxifen may produce unintended loss or gain of weight. This should be mild, Drugs.com reports, and it should end shortly. It also may cause nausea, which may contribute to weight loss by preventing the woman from eating a regular amount of food.
