Generic name: finasteride [ fin-AS-ter-ide ]
Brand names: Propecia, Proscar
Dosage form: oral tablet (1 mg; 5 mg)
Drug class: 5-alpha-reductase inhibitors

Medically reviewed by Melisa Puckey, BPharm. Last updated on May 29, 2024.

What is finasteride?

Finasteride tablets are used for hair loss in men (androgenetic alopecia), to help improve hair growth and hair count over time. Finasteride is also used for benign prostatic hyperplasia (BPH) in men with an enlarged prostate to improve urinary symptoms by reducing prostate size, and may delay the need for surgery. Finasteride is only available as a prescription medicine.

In male-pattern hair loss, a hormone called DHT (dihydrotestosterone) causes hair to become shorter and finer and eventually stop growing in the affected area. DHT also causes the prostate to grow larger. Finasteride works by reducing the amount of DHT available by blocking an enzyme called 5α-reductase, which converts testosterone into DHT. Lower levels of DHT help improve hair growth in male pattern hair loss and reduce symptoms of BPH. Finasteride is from a class of medicines called 5α-reductase inhibitors. 

Finasteride 5mg tablets are used to treat symptomatic benign prostatic hyperplasia (BPH) in men, and finasteride 1mg tablets are used to treat male pattern hair loss in men. 

Finasteride’s first FDA approval was under the brand name Proscar (finasteride 5mg tablets) on June 19, 1992, for benign prostatic hyperplasia (BPH) in men with an enlarged prostate. Propecia (finasteride 1 mg tablets) became FDA-approved for male pattern hair loss (androgenetic alopecia) in men on December 19, 1997. Finasteride is now available as a generic medicine.

Topical finasteride for hair loss has been tested in clinical trials for men with male pattern hair loss, with results showing it to have a similar effect of improving hair count as oral finasteride tablets. The study used a topical solution of finasteride 0.25% w/w (concentration of 2.275 mg/mL) and was a randomized, double‐blind, double-dummy, parallel‐group, 24‐week study. Topical finasteride is not an FDA-approved medicine.

Finasteride side effects

Common finasteride side effects

Common side effects of finasteride 1mg tablets include a decreased interest in sex, erectile dysfunction, and ejaculation disorder. These side effects occurred in 1% or more of patients taking finasteride and greater than the patients treated with placebo in clinical trials. 

Common side effects of finasteride 5 mg tablets may include a failure to have or maintain an erection (impotence), decreased interest in sex, decreased volume of ejaculate, breast enlargement, breast tenderness, and rash. These side effects occurred in 1% or more of patients taking finasteride and greater than the patients treated with placebo in clinical trials. 

The sexual side effects of finasteride may continue after you stop taking this medicine. Talk to your doctor if you have concerns about these side effects.

Serious finasteride side effects

Get emergency medical help if you have signs of an allergic reaction, such as hives, difficulty breathing, or swelling of your face, lips, tongue, or throat.

Call your doctor at once if you notice any signs of male breast cancer, such as:

• breast pain or lumps;
• nipple discharge; or
• any other breast changes.

Tell your doctor right away if you have:

• blood in your semen;
• pain in your testicles; or
• depression.

It may be harder for you to get a woman pregnant while you are using finasteride.

This is not a complete list of side effects, and others may occur. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Warnings

Finasteride should never be taken by a woman or a child.

Finasteride can be absorbed through the skin. Finasteride can cause birth defects if a woman is exposed to it during pregnancy. The tablets should not be handled by a woman who is pregnant or who may become pregnant.

Using this medicine may increase your risk of developing prostate cancer. Your doctor will perform tests to make sure you do not have other conditions that would prevent you from safely using this medicine.

Call your doctor at once if you notice any breast lumps, pain, nipple discharge, or other breast changes. These may be signs of male breast cancer.

Before taking this medicine

You should not use finasteride if you are allergic to it, or any of the inactive ingredients. Using finasteride may increase your risk of developing a serious form of prostate cancer. Ask your doctor about this risk.

Tell your doctor if you have ever had:

• prostate cancer; or
• liver disease or abnormal liver function tests.

Finasteride can cause birth defects if a woman is exposed to it during pregnancy. A broken finasteride tablet should not be handled by a woman who is pregnant or may become pregnant. The medicine from a broken tablet could be absorbed through the skin.

If a woman accidentally comes into contact with a broken or crushed tablet, wash the area with soap and water right away.

How should I take finasteride?

Take a tablet with a full glass of water once a day at the same time each day.

It may be taken with or without meals.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

You may not fully benefit from this medicine for up to 3 months or longer. Use finasteride regularly for the best results.

Your doctor will need to check your progress on a regular basis. 

For benign prostatic hyperplasia, you will need frequent prostate specific antigen (PSA) tests to check for prostate cancer.

Tell your doctor if you stop taking finasteride on a regular basis because this could affect your PSA test results.

Store this medicine at room temperature, away from moisture, heat, and light. When not in use, keep the tablets in the original container, tightly closed.

Finasteride dosing information

Adult Finasteride Dose for Male Pattern Hair Loss:

Usual dose: 1 mg tablet orally once a day. 

Comments:
Daily use for 3 months or more is needed before a benefit can be seen. Continued use is recommended to sustain benefits.
Withdrawal of treatment leads to reversal of effect within 12 months.

Use: For treatment of male pattern hair loss (androgenetic alopecia) in men only. The safety and efficacy have been demonstrated in men between 18 to 41 years of age with mild to moderate hair loss of the vertex and anterior mid-scalp area.

Adult Finasteride Dose for Benign Prostatic Hyperplasia:

Usual dose: 5 mg tablet orally once a day (usual dose)

Comments:
Dosing is the same both in monotherapy and in combination therapy.

What happens if I miss a dose?

Skip the missed dose and use your next dose at the regular time. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking finasteride?

Do not share finasteride with another person, even if they have the same symptoms you have.

What other drugs will affect finasteride?

Other drugs may affect finasteride, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all other medicines you use.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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