URL of this page: http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202649.html

Finasteride (fin-AS-tur-ide) belongs to the group of medicines called enzyme inhibitors. It is used to treat urinary problems caused by enlargement of the prostate (benign prostatic hyperplasia or BPH). In men with very enlarged prostates and mild to moderate symptoms (difficulty urinating, decreased flow of urination, hesitation at the beginning of urination, getting up at night to urinate), finasteride may decrease the severity of symptoms. Finasteride may also reduce the chance that surgery on the prostate will be needed.

Finasteride blocks an enzyme called 5-alpha-reductase, which is necessary to change testosterone to another hormone that causes the prostate to grow. As a result, the size of the prostate is decreased. The effect of finasteride on the prostate lasts only as long as the medicine is taken. If it is stopped, the prostate begins to grow again.

Finasteride also is used by some balding men to stimulate hair growth. If hair growth is going to occur with the use of finasteride, it usually occurs after the medicine has been used for about 3 months and lasts only as long as the medicine continues to be used. The new hair will be lost within 1 year after finasteride treatment is stopped.

Finasteride is available only with your doctor's prescription, in the following dosage form:

Oral
• Tablets (U.S. and Canada)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For finasteride, the following should be considered:

Allergies¡ªTell your doctor if you have ever had any unusual or allergic reaction to finasteride. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy¡ªWomen who are or may become pregnant should not take finasteride or should not be exposed to broken or crushed finasteride tablets, because it can cause changes in the genitals (sex organs) of male fetuses.

Older adults¡ªThis medicine has been tested and has not been shown to cause different side effects or problems in older people than it does in younger adults.

Other medicines¡ªAlthough certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your health care professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.

Finasteride tablets may be crushed to make them easier to swallow. However, women who are or may become pregnant should not handle crushed finasteride tablets.

For patients taking this medicine for benign prostatic hyperplasia (BPH):

• To help you remember to take your medicine, try to get into the habit of taking it at the same time each day.
• Remember that this medicine does not cure BPH but it does help reduce the size of the prostate. Therefore, you must continue to take it if you expect to keep the size of your prostate down. You may have to take this medicine for at least 6 months to see the full effect. You may have to take this medicine for the rest of your life. Do not stop taking this medicine without first discussing it with your doctor.
• This medicine helps to reduce urinary problems in men with BPH. In general, it is best to avoid drinking fluids, especially coffee or alcohol, in the evening. Then your sleep will not be disturbed by your need to urinate during the night.

For individuals taking this medicine for hair growth:

• You may have to take this medicine for at least 3 months to see an effect. The effect will last only as long as the medicine continues to be used. The new hair will be lost within 1 year after finasteride is stopped.

Dosing¡ª

The dose of finasteride will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average dose of finasteride. If your dose is different, do not change it unless your doctor tells you to do so:

• For oral dosage form (tablets):
  • For treatment of benign prostatic hyperplasia (BPH):
    • Adults¡ª5 milligrams (mg) once a day.
  • For hair growth:
    • Adults¡ª1 mg once a day.

Missed dose¡ª

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage¡ª

To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

Women who are or who may become pregnant should not handle crushed finasteride tablets. There is a risk that the medicine could get into the pregnant woman's body and cause birth defects in a male fetus.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• Less common
  • Breast enlargement and tenderness;  skin rash;  swelling of lips 
  
  

  Breast enlargement and tenderness, skin rash and swelling of lips are more likely to occur with the 5-mg dose.

Other side effects may occur that usually do not need medical attention. The following side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

• Less common or rare
  • Abdominal pain;  back pain;  decreased libido (decreased interest in sex);  decreased volume of ejaculate (decreased amount of semen);  diarrhea;  dizziness;  headache ;  impotence (inability to have or keep an erection)  
  
  

  A decrease in the amount of semen during ejaculation should not affect your sexual performance and is not a sign of any change in fertility.

• Incidence Unknown
  • Testicular pain 
  
  

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.

In the U.S.¡ª

In Canada¡ª

• Benign prostatic hyperplasia therapy agent; hair growth stimulant, alopecia androgenetica (systemic)