What is finasteride (Proscar)? How does it work (mechanism of action)?
The prostate gland is located around the tube which empties urine from the bladder (urethra). As the prostate gland enlarges, usually after 50 years of age, it can obstruct or partially block the urine flow. This leads to symptoms which include dribbling of urine, narrow stream, problems starting urine flow, interruption while urinating, and a feeling of incomplete emptying. Other symptoms include wetting and staining of clothes, urinary burning, and urgency.
Prostate gland enlargement (benign prostatic hyperplasia or BPH), is directly dependent on DHT (a hormone converted from the male hormone testosterone). Finasteride inhibits the enzyme necessary for the conversion of testosterone to DHT in the prostate. Therefore, administration of finasteride lowers blood and tissue DHT levels and helps reduce the size of the prostate gland.
Although reductions in the size of the prostate gland can occur in virtually all the patients who take finasteride, only 50% will experience improvement in the symptoms of BPH. Patients generally respond to finasteride in several weeks, but it often takes 6 months for the patient to receive the full effect of the drug.
What are the side effects of finasteride?
Side effects are rare but can include impotence and decreased sex drive. Finasteride should not be used by women, children, or male partners of women trying to become pregnant. Finasteride should not be used until a thorough prostate examination has been done to exclude cancer, stricture, or infection in the gland. Rarely, cases of male breast cancer have been reported.
What is the dosage for finasteride?
Finasteride is metabolized mainly by the liver, and caution should be used in patients with liver dysfunction. Finasteride may be taken with or without food.
Which drugs or supplements interact with finasteride?
Drug interactions are generally not a problem.
Is finasteride safe to take if I’m pregnant or breastfeeding?
Finasteride causes abnormal development of the sexual organs of the male fetus. Therefore, women who are pregnant or are likely to be pregnant should not handle crushed or broken finasteride tablets in order to prevent absorption through the skin.
Finasteride is not prescribed for women.
What else should I know about finasteride?
What preparations of finasteride are available?
How should I keep finasteride stored?
Finasteride should be stored at room temperature in a tight, light resistant container.
Finasteride is available in generic form, but you must have a prescription from your doctor or other health-care professional to obtain the drug.
Medically Reviewed on 3/20/2019
FDA Prescribing Information