Megestrol Acetate

Definition

Megestrol acetate is used to treat unexplained weight loss during cancer therapy and to stop new cell growth in some cancers. Megestrol acetate is also known by the brand name Megace.

Purpose

Megestrol acetate is used to treat some advanced hormone-responsive cancers of the breast, kidney, and uterus. It is also used in larger doses to help reverse weight loss for which there is no other treatable cause.

Description

Megestrol acetate is a synthetic derivative of the female hormone progesterone. In healthy women, progesterone plays a major role in preparing the uterus for pregnancy. It has been approved by the Food and Drug Administration (FDA), and its use is usually covered by insurance.

Exactly why megestrol acetate stops tumor growth is unclear. Many tumors are sensitive to hormones. It appears that megestrol acetate, in some way, changes the hormonal climate of the tumor so that cells stop responding to other hormones and proteins that would normally stimulate their growth. This drug cannot tell the difference between normal cells and cancer cells, so some normal cells are also killed during treatment. But since cancer cells grow more rapidly than normal cells, more cancer cells are killed.

Megestrol acetate has another independent use in cancer treatment. In high doses, it is used to counteract weight loss that does not occur for any other treatable reason. Megestrol acetate appears to bring about weight gain through increased fat storage.

Recommended dosage

Megestrol acetate comes in both liquid and tablet form. To treat weigh loss, the standard dosage is a single dose given in the morning with breakfast. Many clinical studies are underway to examine the best use of megestrol acetate in severe weight loss. Most of these studies are for people who are losing weight because they suffer with AIDS. However, the selection of clinical trials underway changes frequently. Current information on what clinical trials are available and where they are being held can be found by entering the search term "megestrol acetate" at the following websites:

• National Cancer Institute <http://cancertrials.nci.nih.gov> or (800) 4-CANCER
• National Institutes of Health Clinical Trials <http://clinicaltrials.gov>
• Center Watch: A Clinical Trials Listing <http://www.centerwatch.com>.

To reduce tumor growth, the dose of megestrol acetate is individualized, and depends on the type of cancer, the patient's body weight and general health, what other drugs are being given, and the way the cancer responds to hormones. A standard dose of Megace to treat breast cancer is 160 mg/day divided into four doses. A standard dose for endometrial cancer (cancer of the uterus) is 40-320 mg/day in divided doses. Treatment normally continues for about two months.

Precautions

Women taking megestrol acetate should not get pregnant. Megestrol acetate is believed to cause birth defects in babies born to mothers who are taking the drug. A patient assistance program is available through Bristol Meyer Squibb, the manufacturer of this drug at (800) 332-2056.

Side effects

Megestrol acetate has several rare but serious side effects. Some people have been reported to develop Cushing's syndrome. This is a hormonal imbalance in which people (usually women) develop fatty deposits in the face and neck, lose bone mass (osteoporosis), stop menstruating, develop diabetes, high blood pressure, and other signs of fluid and salt (electrolyte) imbalances.

Other common side effects of megestrol acetate include:

• worsening of diabetic symptoms
• pain in the chest or abdomen
• infection
• sarcoma (tumors of the skin or connective tissue)
• irregular heartbeat
• fluid retention
• breakthrough vaginal bleeding
• blood clots in legs or lungs
• nausea or constipation
• dry mouth or increased salivation
• abnormal white blood cell count
• confusion or abnormal thinking
• emotional and psychological changes
• rash, itching, abnormal sweating, or skin disorders
• cough, sore throat, lung disorders
• hair loss (alopecia)
• uncontrolled urination or urinary tract infection
• male impotence

Interactions

No specific interactions with other pharmaceuticals have been reported in people using megestrol acetate. However, many drugs interact with nonprescription (over-the-counter) drugs and herbal remedies as well as prescription drugs. Patients should always tell their health care providers about all remedies they are taking. Patients should also mention if they are on a special diet such as low salt or high protein.

Tish Davidson, A.M.

Food and Drug Administration (FDA)

—The government agency that oversees public safety in relation to drugs and medical devices, and gives the approval to pharmaceutical companies for commercial marketing of their products in the U.S.

Hormone

—A chemical released by a gland that travels through the circulatory system and affects only the tissues at a distance from its release point that have receptors for the chemical.

Progesterone

—A female hormone that prepares the uterus for pregnancy.