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Drug Profile

Do NOT stop taking this or any drug without the advice of your physician. Some drugs can cause severe adverse effects when they are stopped suddenly.

Do Not Use [what does this mean?]
Generic drug name: finasteride (fin AS tur ide)
Brand name(s): PROPECIA, PROSCAR
GENERIC: available FAMILY: 5-Alpha Reductase Inhibitors
Find the drug label by searching at DailyMed.

Pregnancy and Breast-feeding Warnings [top]

Pregnancy Warning

Women should not handle crushed or broken finasteride tablets when they are pregnant or may potentially be pregnant because of the possibility of absorption of finasteride and the subsequent potential risk of abnormalities of the external genitalia of a male fetus. Proscar tablets are coated and will prevent contact with the active ingredient finasteride during normal handling, provided that the tablets have not been broken or crushed.

Safety Warnings For This Drug [top]

A possible association between finasteride use and male breast cancer was revealed in a large clinical trial when four cases of breast cancer were reported in men taking finasteride. This rate is nearly 200 times greater than what is seen in men in the general population (see Benign Prostatic Hypertrophy (BPH)).

Do not use finasteride to prevent prostate cancer. The use of this drug for cancer prevention has resulted in more aggressive cancer in men who do develop prostate cancer (see Benign Prostatic Hypertrophy (BPH)).

Facts About This Drug [top]

Do Not Use: With use of this drug, there is an increased risk of being diagnosed with a more serious form of prostate cancer.

Finasteride (PROSCAR) is used to control symptoms of enlarged prostate (benign prostatic hyperplasia [BPH]). Enlargement of the prostate gland impedes urination, causing a weak stream, double voiding, inability to empty the bladder completely and urinary tract infections. BPH affects 50% of men over age 60 and 90% of men in their 70s and 80s.[1]


Do Not Use: With use of this drug, there is an increased risk of being diagnosed with a more serious form of prostate cancer.

Finasteride (PROSCAR) is used to control symptoms of enlarged prostate (benign prostatic hyperplasia [BPH]). Enlargement of the prostate gland impedes urination, causing a weak stream, double voiding, inability to empty the bladder completely and urinary tract infections. BPH affects 50% of men over age 60 and 90% of men in their 70s and 80s.[1]

Finasteride blocks an enzyme called 5-alpha reductase that is necessary to convert the male sex hormone, testosterone, to another hormone that causes the prostate to grow. As a result, the size of the prostate gland is decreased.

Alternatives for the treatment of BPH

The other family of drugs approved by the Food and Drug Administration (FDA) to treat BPH is the alpha-blockers. These drugs are preferred to finasteride and are discussed here.

If your BPH symptoms are minimal, no treatment is necessary, no matter the size of your prostate gland. If you have BPH symptoms and do not have a very enlarged gland, then one of the alpha-blockers — alfuzosin (UROXATRAL), doxazosin (CARDURA), silodosin (RAPAFLO), tamsulosin (FLOMAX) or terazosin (HYTRIN) would be your best choice. If your prostate is more enlarged, treatment with an alpha-blocker would again be the best choice. You should not use finasteride to prevent prostate cancer or to treat BPH.[2]

Surgical procedures are also an option for men with severe symptomatic BPH, in addition to the alpha-blockers.[3]

Finasteride for treatment of prostate cancer

A urologist from the Memorial Sloan-Kettering Cancer Center in New York stated in an editorial that “On balance, finasteride does not seem to be an attractive agent for the chemoprevention of prostate cancer.” Public Citizen agrees.[4],[5] It also should be noted that the prevention of prostate cancer is not an FDA-approved use of finasteride.[2]

The question of whether or not to take finasteride to prevent prostate cancer was addressed in an article in The Medical Letter on Drugs and Therapeutics. According to the author, “Until more data become available, the conservative course would be not to take it."[6]

Studies show …

A large clinical trial compared the effect of finasteride with that of the older first-generation alpha-blocker terazosin (HYTRIN) in more than 1,000 men with BPH. The study lasted one year. Overall, it concluded that terazosin was effective therapy, finasteride was not and the combination of terazosin and finasteride was not more effective than terazosin alone. However, the researchers did find that finasteride was effective in a group of men with very large glands, while terazosin was effective in men with a very large or smaller prostate gland.[7]

Another study found that long-term use of finasteride reduces the probability of surgery for an enlarged prostate gland.[8] But the editorial accompanying this study took a different view: “Treatment with finasteride to prevent these complications may be unwarranted for most men with symptoms of this disorder [BPH].” The editorial relates a hypothetical conversation between a man asking about finasteride and reducing the risk of prostate surgery and a very good doctor who explains the results of the study.

Patient: Doctor, my wife just read about this new drug for the prostate. She said it was like an insurance policy. You pay a little premium each day to avoid needing surgery later.

Physician: That is a good way to think about it. After four years, 13 of 100 men had complete urine blockage or needed surgery for their prostate. A drug called finasteride reduced the chances of these problems; instead of occurring in 13 of 100 men, they occurred in 7 of 100. In other words, about 6 out of 100 men benefited after four years of taking the drug.

Patient: So 100 men paid the premium for four years and 6 of them got the benefit?

Physician: You seem to have the basic point. Those men who kept taking the drug also said that their urinary symptoms were a little better - an improvement of 2 points on a 35-point scale. But a few men taking the drug had impotence, breast tenderness and loss of energy.[9]

High-grade prostate cancer

In 2004, the FDA required Merck, the manufacturer of finasteride, to revise its product label to include information from the Prostate Cancer Prevention Trial (PCPT).[2] This study, published in 2003 in The New England Journal of Medicine, examined the impact of daily treatment with 5 milligrams (mg) of finasteride on the development of prostate cancer in men with healthy prostates. It found that men in the finasteride group developed fewer cancers than those receiving a placebo (18.4% versus 24.3%, an absolute risk difference of 6%), but several important problems developed as well.[4]

First, because the men in the study were tested more aggressively for prostate cancer than men in the general population, it is likely that the study detected low-grade tumors of little clinical significance that would otherwise not have been detected. What’s more, a higher proportion of the patients taking finasteride developed higher-grade tumors, which are more aggressive and present a greater risk. In 2011, the FDA advised that men aged 55 and older who had a normal digital rectal examination and took finasteride 5 mg/day in the seven-year PCPT trial had an increased risk of high-grade prostate cancer. For more details on the results of PCPT, click here.

In March 2012, Health Canada (a regulatory agency equivalent to the FDA) issued a warning concerning the use of finasteride and dutasteride and an increased risk of developing a serious, high-grade form of prostate cancer.[10]

Suicidal thoughts[11],[12],[13]

Several observational studies have found an association between the use of finasteride and suicidal thoughts. Another study also found an increased risk of self-harm among finasteride users.[14] Such evidence prompted French drug regulators to add this adverse effect to the labeling of finasteride products starting in early 2018.[15]

In a May 2021 Worst Pills, Best Pills News article, we highlighted a report that Merck &Co, the manufacturer of Propecia, and the FDA have been aware for years of reports of suicidal thoughts and behavior in men and did not add a warning to the drug product label. Read more here.[16]

Male breast cancer

A monthly newsletter published by the Medicines and Healthcare products Regulatory Agency (the U.K. government agency responsible for ensuring that medicines and medical devices work and are acceptably safe) stated that cases of male breast cancer have been reported in clinical trials and in postmarketing reports with finasteride use. According to the article, 50 such cases of male breast cancer had been reported worldwide by November 2009.[17]

In August 2011, Health Canada announced that it was updating the drug label information for finasteride to include safety information on rare reports of breast cancer in men. The update included information that male breast cancer has been reported in a small number of patients worldwide with both the 1-mg and 5-mg formulations of finasteride. The update also stated that most of the reports have been associated with the 5-mg formulation.[18]

Possible risk of seizures

In 2014, an article was published in the World Health Organization’s WHO Pharmaceuticals Newsletter suggesting a link between the use of finasteride and seizures.[19]

Possible risk of type 2 diabetes

In 2019, the BMJ published results of a study showing an increased risk of type 2 diabetes in men using 5-alpha reductase inhibitor drugs compared with men using the alpha blocker tamsulosin.[20]

Before You Use This Drug [top]

Tell your doctor if you have or have had:

  • allergy to finasteride or any of its components
  • liver problems
  • difficulties urinating

Tell your doctor about any other drugs you take, including aspirin, herbs, vitamins, and other nonprescription products.

Before you start this drug, have your doctor do a digital rectal exam and baseline PSA test, and check that you do not have conditions with similar symptoms, such as infection, prostate cancer, stricture disease, or hypotonic bladder.

When You Use This Drug [top]

  • Do not let any women who are pregnant or could become pregnant crush your tablets or touch your medication.
  • Use a condom to protect any women you have intercourse with from pregnancy, since finasteride in semen can harm the fetus.
  • Do not drink alcohol or coffee in the evening.
  • Rule out the presence of prostate cancer before starting this drug.
  • Read information about your prescription each time you refill it in case new information has become available.

How to Use This Drug [top]

  • If you miss a dose, take it as soon as you remember, but skip it if it is almost time for the next dose. Do not take double doses.
  • Do not share your medication with others.
  • Take the drug at the same time(s) each day.
  • Take with or without food.
  • Swallow tablets whole or crushed.
  • Store at room temperature with lid on tightly. Do not store in the bathroom. Do not expose to heat, moisture, or strong light. Keep out of reach of children.
  • Check with your doctor before discontinuing finasteride.

Interactions with Other Drugs [top]

Evaluations of Drug Interactions 2003 lists no drugs, biologics (e.g., vaccines, therapeutic antibodies), or foods as causing “highly clinically significant” or “clinically significant” interactions when used together with the drugs in this section. We also found no interactions in the drugs’ FDA-approved professional package inserts. However, as the number of new drugs approved for marketing increases and as more experience is gained with these drugs over time, new interactions may be discovered.

Adverse Effects [top]

Call your doctor immediately if you experience:

  • pelvic or testicular pain
  • skin rash
  • swelling of lips
  • breast enlargement or tenderness

Call your doctor if these symptoms continue:

  • abdominal pain
  • back pain
  • decreased amount of ejaculation
  • dizziness
  • gas
  • headache
  • impotence
  • diarrhea
  • testicular pain

Periodic Tests[top]

Ask your doctor which of these tests should be done periodically while you are taking this drug:

  • digital rectal examination

last reviewed May 31, 2021