Dictionary:

antiandrogen

  (ăn'tē-ăn'drə-jən, ăn'tī-)

A substance that inhibits the biological effects of androgenic hormones.

Key Terms: Adrenal gland, Food and Drug Administration, LHRH agonists, Monotherapy.

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

Antiandrogens are approved by the Food and Drug Administration (FDA) for the treatment of prostate gland cancer that has spread to other areas of the body.

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 luteinizing 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; thus the combination of the two types of agents has improved survival in prostate cancer patients.

Newer trends in antiandrogen therapy include intermittent treatment with the drugs rather than continuous dosage; and antiandrogen monotherapy for patients whose cancer is still localized. Monotherapy means that the patient is given only the antiandrogen drugs without any LHRH agonists. As of late 2003, however, antiandrogen monotherapy is considered an investigational treatment.

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, tiredness, and impotence (the inability of males to have sexual intercourse).

Antiandrogens can also 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.

These drugs must be used with caution in patients who are receiving the blood-thinning drug Coumadin (warfarin) or the drugs phenytoin and theophylline. Combining these drugs with antiandrogen therapy may increase the effects or side effects of these agents.

Another potentially troublesome side effect of anti-androgens is bone loss. Men who are taking these drugs are at increased risk of osteoporosis and consequent bone fractures. Doctors are now recommending that male patients taking these drugs should have a baseline assessment of their bone mineral density, and should be given zoledronic acid (Zometa) if there is evidence of serious bone loss.

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.

Resources

Periodicals

Cooperberg, M. R., E. J. Small, A. D'Amico, and P. R. Carroll. "The Evolving Role of Androgen Deprivation Therapy in the Management of Prostate Cancer." Minerva Urologica e Nefrologica 55 (December 2003): 219–238.

Higano, C. S. "Management of Bone Loss in Men with Prostate Cancer." Journal of Urology 170, 6 pt. 2 (December 2003): S59–S63.

Holzbeierlein, J. M., E. P. Castle, and J. B. Thrasher. "Complications of Androgen-Deprivation Therapy for Prostate Cancer." Clinical Prostate Cancer 2 (December 2003): 147–152.

Morote, J., E. Martinez, E. Trilla, et al. "Osteoporosis During Continuous Androgen Deprivation: Influence of the Modality and Length of Treatment." European Urology 44 (December 2003): 661–665.

Organizations

American Urological Association (AUA). 1000 Corporate Boulevard, Linthicum, MD 21090. (866) RING-AUA or (410) 689-3700. .

United States Food and Drug Administration (FDA). 5600 Fishers Lane, Rockville, MD 20857-0001. (888) INFO-FDA (463-6332). .

—Nancy J. Beaulieu, RPh., BCOP; Rebecca J. Frey, PhD

Any substance capable of inhibiting the biological effects of androgenic hormones.

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