Antiandrogens

Definition

Antiandrogens, including flutamide (brand name Eulexin or Euflex), bicalutamide (brand name Casodex), and nilutamide (brand name Nilandron), are medicines used in the treatment of advanced prostate cancer.

Purpose

Antiandrogen therapy stops or blocks the effect androgen presence has on tumor cells of the prostate. Antiandrogens are combined with either surgery or drug therapy that shuts down male hormone production. The common drugs used with antiandrogens are known as leuteinizing hormone releasing hormone (LHRH) agonists, referred to by the brand names Lupron or Zoladex. The LHRH agonists produce side effects that the antiandrogens can keep under control and the combination of the two agents has improved survival in prostate cancer patients.

Description

Antiandrogens will not cure prostate cancer, but they will help improve some of the disease's symptoms. They may also increase survival time.

Androgens are made naturally in the body and include the hormone testosterone and its related compound, dihydrotestosterone. The testes produce the majority of testosterone. The adrenal glands also produce androgens in smaller amounts. Prostate cancer cells grow due to normal levels of androgens produced by the body. Some patients have prostate tumors that are extra-sensitive to androgens in the blood. The androgens attach to receptors on the tumor cells and send a signal to the tumor cells causing them to grow and multiply. Antiandrogen drugs block the receptors on the prostate cancer cell that are sensitive to the androgen hormones. By blocking these receptors, known as androgen-receptors, the cancer cells cannot be instructed to grow and multiply. Antiandrogens also cause the body to decrease production of androgens and, as a result, their effects.

Recommended dosage

Flutamide

Flutamide is an oral capsule dosed at 250 mg three times a day in combination with the LHRH agonist or surgical removal of the testis.

Bicalutamide

Bicalutamide is an oral tablet dosed at 50 mg once a day in combination with the LHRH agonist. The dose may need to be decreased in patients with decreased liver function.

Nilutamide

Nilutamide is an oral tablet dosed at 300 mg once a day for 30 days then 150 mg once a day in combination with surgical removal of the testis.

Precautions

Although antiandrogens are primarily given to men, women taking them should avoid pregnancy. Antiandrogens block the male hormone called testosterone and, as a result, can adversely affect the developing fetus. Blood counts will be monitored while on antiandrogen therapy.

Side effects

The most common side effects from all antiandrogens are due to the decreased levels of hormones. These commonly include hot flashes, loss of sex drive, and impotence (the inability of males to have sexual intercourse).

Antiandrogens can cause mild nausea, vomiting, diarrhea, loss of appetite, enlarged breasts or breast tenderness, skin reactions, muscle aches, liver problems, blood in the urine and generalized pain and decrease in blood counts. Nilutamide may cause visual disturbances, with patients having difficulty with the dark. Rarely, lung problems have occurred due to nilutamide or bicalutamide, including cough and shortness of breath.

Use with caution in patients who are receiving the blood-thinning drug warfarin or the drugs phenytoin and theophylline. Combining these drugs with antiandrogen therapy may increase the effects or side effects of these agents.

Interactions

Patients should tell their doctors if they have a known allergic reaction to antiandrogens or any other medications or substances, such as foods and preservatives. Before taking any new medications, including non-prescription medications, vitamins, and herbal medications, the patients should notify their doctors.

Nancy J. Beaulieu, RPh., BCOP

Adrenal gland

—Small organ located above the kidneys that produce hormones.

Food and Drug Administration

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

LHRH agonists

—Luteinizing hormone-releasing hormone drugs that initially stimulate the testes to make and release testosterone. With time, as the amount of testosterone in the blood rises, it stops the production of luteinizing hormone, which results in stopping overall production of testosterone.