Finasteride

What it is

• Finasteride belongs to a class of medicines called 5-alpha reductase inhibitors.
• It comes as a tablet taken by mouth.
• Propecia and Proscar are brand names of finasteride.

Source: MedlinePlus (NIH): Finasteride: MedlinePlus Drug Information ↗

How it's thought to work

• For an enlarged prostate, finasteride works by blocking the body's production of a male hormone that makes the prostate grow.
• For hair loss, it works by blocking a male hormone in the scalp that stops hair growth.
• Finasteride stops testosterone from changing into DHT, a hormone needed for normal development of male genitals.
• Balding scalp has more DHT, and finasteride lowers DHT in the scalp and blood.

Sources: MedlinePlus (NIH): Finasteride: MedlinePlus Drug Information ↗ · DailyMed (FDA drug label): DailyMed - PROPECIA- finasteride tablet, film coated ↗

What people use it for

• Propecia is approved to treat male pattern hair loss in men only.
• Proscar is not approved to prevent prostate cancer.
• For hair loss, MedlinePlus says it may take at least 3 months before any improvement is seen.

Sources: DailyMed (FDA drug label): DailyMed - PROPECIA- finasteride tablet, film coated ↗ · DailyMed (FDA drug label): DailyMed - PROSCAR- finasteride tablet, film coated ↗ · MedlinePlus (NIH): Finasteride: MedlinePlus Drug Information ↗

What the research has found so far

On Finasteride and aging, PubMed lists 76 trials in people, 87 studies that watched people over time, 62 animal and lab studies. See the counts and searches

Side effects and risks

• MedlinePlus lists erection problems, lower sexual desire, ejaculation problems and testicle pain.
• Serious side effects listed include allergic reactions such as rash, hives, swelling and trouble breathing.
• Serious side effects listed also include new or worsening depression and thoughts of self-harm.
• In Propecia trials, the most common reactions were lower libido, erectile dysfunction and ejaculation disorder.
• MedlinePlus says finasteride may lower fertility in men.
• In studies, single doses up to 400 mg and daily doses up to 80 mg for three months did not cause adverse reactions.

Sources: MedlinePlus (NIH): Finasteride: MedlinePlus Drug Information ↗ · DailyMed (FDA drug label): DailyMed - PROPECIA- finasteride tablet, film coated ↗

Who should be careful, and drug interactions

• Finasteride is not for use by women who are or may be pregnant, because it may cause abnormal genitals in a male baby.
• Pregnant women or those who may become pregnant should not handle crushed or broken tablets.
• Coated tablets prevent contact with the drug during normal handling if they are not broken or crushed.
• Finasteride is for use only in men.
• The labels say safety and effectiveness have not been established in children.
• The label says caution is needed in people with liver problems, since the liver breaks down finasteride extensively.
• MedlinePlus lists liver disease and prostate cancer as conditions to tell a doctor about.
• The label found no drug interactions of clinical importance.
• Warfarin, digoxin, propranolol, theophylline and antipyrine showed no clinically meaningful interactions in tests.
• Finasteride is contraindicated, meaning should not be used, in people with hypersensitivity (allergy) to any component.
• Finasteride lowers PSA, a blood test marker for prostate cancer, by about 50%.

Sources: DailyMed (FDA drug label): DailyMed - PROSCAR- finasteride tablet, film coated ↗ · MedlinePlus (NIH): Finasteride: MedlinePlus Drug Information ↗ · DailyMed (FDA drug label): DailyMed - PROPECIA- finasteride tablet, film coated ↗

Approval and legal status

• FDA: DailyMed - PROPECIA- finasteride tablet, film coated ↗

Amounts used in studies

What studies or labels describe, not a recommendation.

• The label lists one 5 mg Proscar tablet once a day for an enlarged prostate.
• The label lists one 1 mg Propecia tablet once daily for hair loss.
• The labels say it may be taken with or without meals.
• The label says daily use for three months or more is generally needed before benefit is seen for hair loss.

Sources: DailyMed (FDA drug label): DailyMed - PROSCAR- finasteride tablet, film coated ↗ · DailyMed (FDA drug label): DailyMed - PROPECIA- finasteride tablet, film coated ↗

Roughly what it costs

The 2 products we list that contain Finasteride cost from $22 to $35, as read from the makers' pages. See the products

Questions to ask your doctor

• Is Finasteride a sensible option for me, given my health and the medicines I take?
• Could Finasteride interact with any medicine or supplement I already take?
• What side effects should I watch for, and when should I stop or call you?
• Would Finasteride be used for its approved purpose, or off-label for aging?
• How would we tell whether it is helping, and when should we review it?