Finasteride is a drug that belongs to the class of androgen inhibitors, which means that it blocks the production of male sex hormones. It is sold in the United States and Canada under the brand names Proscar and Propecia.
Finasteride has two main purposes: the treatment of urinary problems in men caused by benign prostatic hypertrophy (BPH) or enlargement of the prostate gland; and the stimulation of new hair growth in men with male pattern baldness. Finasteride was first approved by the Food and Drug Administration (FDA) in 1992 under the trade name Proscar as a treatment for BPH. It received a second FDA approval in December 1997 under the trade name Propecia for the treatment of hair loss in men. Finasteride has also been used by some European doctors to treat hair loss in postmenopausal women, although its use in women is considered controversial in the United States. It is considered the most effective nonsurgical treatment for male pattern baldness as of 2005.
Finasteride works to relieve such symptoms of prostate enlargement as urinary urgency, the need to urinate frequently at night (nocturia), inability to completely empty the bladder, incontinence, or painful urination (dysuria) by blocking the production of DHT. DHT causes the prostate gland to grow and increase pressure on the bladder. As the swollen prostate gradually shrinks, the patient finds it easier to pass urine without discomfort and to empty the bladder completely before going to sleep. Some doctors also prescribe finasteride as pretreatment for prostate surgery, as it lowers the risk of severe bleeding during the operation.
As of early 2005, the National Cancer Institute (NCI) was evaluating finasteride as a possible chemo preventative for prostate cancer in selected patients. Researchers were not yet certain, however, which men might benefit most from taking the drug.
Finasteride inhibits the body's production of an enzyme called 5-alpha-reductase, which is needed to convert testosterone to another androgen called 5-alpha-dihydrotestosterone (DHT). Finasteride is a white powder that can be dissolved in alcohol or chloroform but is very difficult to dissolve in water. Both Proscar and Propecia are manufactured as coated tablets to be taken by mouth.
- Proscar: Finasteride for treatment of an enlarged prostate is taken once a day as a 5-mg tablet. The pill may be crushed or broken if the patient finds it hard to swallow.
- Propecia: Finasteride for hair regrowth is taken once a day as a 1-mg tablet. The drug may be taken with or without meals, as the patient prefers.
Finasteride should be stored in dry places and should be kept at a temperature between 59°F and 86°F (15-30°C). Heat and moisture may cause the drug to lose its potency.
The drug can be safely handled by pregnant women as long as the tablets are intact; however, crushed or broken tablets should not be touched by a pregnant woman as the drug can be absorbed through the skin. If the woman is carrying a male fetus, the drug can cause abnormalities in the baby's sex organs. The FDA issued a warning in 2003 that men taking finasteride should not donate blood until one month after the final dose of the drug, on the grounds that their blood could contain high enough levels of the medication to cause birth defects in a male baby if given to a pregnant woman.
Patients should be advised that finasteride takes several months to reach its full effect—as long as six months for BPH and three months for hair regrowth. In addition, the drug's effects on the body are not permanent; the prostate will start to enlarge again or the hair growth will be lost if the patient stops taking the drug.
Proscar can affect the results of a prostate-specific antigen (PSA) test for cancer of the prostate. Between 30 and 50 percent of men taking the drug will have elevated levels of PSA in their blood serum.
Finasteride should be used cautiously by men with liver disorders.
As of 2005 reported side effects from using finasteride include:
- impotence or loss of interest in sex
- lumps or pain in the breast or a discharge from the nipple
- skin rash, itching, or hives
- swelling of the lips or face
- a smaller quantity of ejaculate during intercourse (which does not affect fertility)
- headaches, dizziness, or diarrhea
- pain in the testicles
These side effects are more common with the 5-mg dose, but usually go away as soon as the drug is discontinued.
As of 2005 finasteride has not been reported to cause significant interactions with other medications.
Alopecia— The medical term for baldness.
Androgens— A group of hormones that produces masculine characteristics.
Chemo preventative— Description of a drug given in order to prevent the development of a specific disease. Finasteride was in 2005 being evaluated as a possible cancer chemo preventative.
Dysuria— Painful or difficult urination.
Incontinence— Inability to control urination or defecation.
Nocturia— Excessive need to urinate at night.
Prostate— A gland in males below the bladder that surrounds the urethra. Enlargement of the prostate may cause problems in urination.
Urgency— A sudden and powerful need to urinate.
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"Benign Prostatic Hyperplasia (Benign Prostatic Hypertrophy)." Section 17, Chapter 218 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers and Robert Berkow. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
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