Hair lossActive ingredient
Finasteride
Type II 5-alpha reductase inhibitor2 FDA labels read
Finasteride is one of two ingredients approved by the FDA for pattern hair loss. It is approved in men only, at 1 mg, under the name Propecia. The same ingredient at 5 mg is approved as Proscar for an entirely different condition, benign prostatic hyperplasia.
Highlights of the labels
- Propecia
- Male pattern hair loss, in men onlycovers hair loss
- Proscar
- Enlarged prostatenot hair loss
- Supply
- Prescription only
- Generic
- 12 approved applications
- Boxed warning
- None in these labels
Brands and what each one is approved for
One active ingredient can hold several separate FDA approvals. They are different documents with different approved uses, and mixing them up is the most common mistake made about these medications.
| Brand | What its label approves | Supply | Label version |
|---|---|---|---|
| PropeciaOrganon LLC | What its label approvesMale pattern hair loss, in men onlyCovers hair loss | SupplyPrescription | Label version14 October 2024 |
| ProscarOrganon LLC | What its label approvesEnlarged prostateNot hair loss | SupplyPrescription | Label version18 March 2026 |
How it works
Finasteride blocks the type II 5-alpha reductase enzyme, which converts testosterone into dihydrotestosterone. The label states that men with male pattern hair loss have higher levels of dihydrotestosterone in balding scalp, and that finasteride lowers both scalp and serum levels of it.
Mechanism of action, Propecia label
Finasteride is a competitive and specific inhibitor of Type II 5α-reductase, an intracellular enzyme that converts the androgen testosterone into DHT. Two distinct isozymes are found in mice, rats, monkeys, and humans: Type I and II. Each of these isozymes is differentially expressed in tissues and developmental stages.
What the FDA approved it for
The approved uses, as worded in the label.
Propecia
- Efficacy in bitemporal recession has not been established.
- PROPECIA is not indicated for use in women.
- PROPECIA is a 5α-reductase inhibitor indicated for the treatment of male pattern hair loss (androgenetic alopecia) in MEN ONLY.
Proscar
- PROSCAR, is a 5α-reductase inhibitor, indicated for the treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate to: Improve symptoms Reduce the risk of acute urinary retention Reduce the risk of the need for surgery including transurethral resection of the prostate (TURP) and prostatectomy.
- PROSCAR administered in combination with the alpha-blocker doxazosin is indicated to reduce the risk of symptomatic progression of BPH (a confirmed ≥4 point increase in American Urological Association (AUA) symptom score).
- Limitations of Use: PROSCAR is not approved for the prevention of prostate cancer.
Forms and strengths
The presentations and strengths listed in the label.
Propecia
PROPECIA tablets (1 mg) are tan, octagonal, film-coated convex tablets with "stylized P" logo on one side and PROPECIA on the other. 1 mg tablets.
Proscar
5-mg blue, modified apple-shaped, film-coated tablets, with the code MSD 72 on one side and PROSCAR on the other. 5-mg film-coated tablets.
How the label says it is taken
What the label states about administration. It is not a dosing instruction for any individual.
Propecia
- PROPECIA may be administered with or without meals.
- The recommended dose of PROPECIA is one tablet (1 mg) taken once daily.
- In general, daily use for three months or more is necessary before benefit is observed.
- Continued use is recommended to sustain benefit, which should be re-evaluated periodically.
Proscar
- PROSCAR may be administered with or without meals.
- Monotherapy: One tablet (5 mg) taken once a day.
- Combination with Doxazosin: One tablet (5 mg) taken once a day in combination with the alpha-blocker doxazosin.
Most common adverse reactions
The adverse reactions the label reports as most common.
Propecia
most common adverse reactions, reported in ≥1% of patients treated with PROPECIA and greater than in patients treated with placebo are: decreased libido, erectile dysfunction and ejaculation disorder.
Proscar
The drug-related adverse reactions, reported in ≥1% in patients treated with PROSCAR and greater than in patients treated with placebo over a 4-year study are: impotence, decreased libido, decreased volume of ejaculate, breast enlargement, breast tenderness and rash.
Warnings and precautions
The warnings and precautions section of the label.
Propecia
- PROPECIA is not indicated for use in women or pediatric patients.
- Women should not handle crushed or broken PROPECIA tablets when they are pregnant or may potentially be pregnant due to potential risk to a male fetus.
- PROPECIA causes a decrease in serum PSA levels.
- Any confirmed increase in PSA while on PROPECIA may signal the presence of prostate cancer and should be evaluated, even if those values are still within the normal range for men not taking a 5α-reductase inhibitor. 5α-reductase inhibitors may increase the risk of high-grade prostate cancer.
Proscar
- PROSCAR reduces serum prostate specific antigen (PSA) levels by approximately 50%.
- However, any confirmed increase in PSA while on PROSCAR may signal the presence of prostate cancer and should be evaluated, even if those values are still within the normal range for men not taking a 5α-reductase inhibitor.
- PROSCAR may increase the risk of high-grade prostate cancer.
- Females should not handle crushed or broken PROSCAR tablets when they are pregnant or may potentially be pregnant due to potential risk to a male fetus.
Contraindications
Situations in which the label states the medication must not be used.
Propecia
- PROPECIA is contraindicated in the following: Pregnancy.
- Finasteride use is contraindicated in women when they are or may potentially be pregnant.
- Because of the ability of Type II 5α-reductase inhibitors to inhibit the conversion of testosterone to 5α-dihydrotestosterone (DHT), finasteride may cause abnormalities of the external genitalia of a male fetus of a pregnant woman who receives finasteride.
- If this drug is used during pregnancy, or if pregnancy occurs while taking this drug, the pregnant woman should be apprised of the potential hazard to the male fetus. In female rats, low doses of finasteride administered during pregnancy have produced abnormalities of the external genitalia in male offspring.
Proscar
- PROSCAR is contraindicated in the following: Hypersensitivity to any component of this medication.
- Finasteride use is contraindicated in females when they are or may potentially be pregnant.
- Because of the ability of Type II 5α-reductase inhibitors to inhibit the conversion of testosterone to 5α-dihydrotestosterone (DHT), finasteride may cause abnormalities of the external genitalia of a male fetus of a pregnant female who receives finasteride.
- If this drug is used during pregnancy, or if pregnancy occurs while taking this drug, the pregnant female should be apprised of the potential hazard to the male fetus. In female rats, low doses of finasteride administered during pregnancy have produced abnormalities of the external genitalia in male offspring.
Drug interactions
Interactions the label singles out.
Propecia
- Cytochrome P450-Linked Drug Metabolizing Enzyme System No drug interactions of clinical importance have been identified.
- Finasteride does not appear to affect the cytochrome P450-linked drug-metabolizing enzyme system.
- Compounds that have been tested in man include antipyrine, digoxin, propranolol, theophylline, and warfarin and no clinically meaningful interactions were found. Other Concomitant Therapy Although specific interaction studies were not performed, finasteride doses of 1 mg or more were concomitantly used in clinical studies with acetaminophen, acetylsalicylic acid, α-blockers, analgesics,...
Proscar
- Cytochrome P450-Linked Drug Metabolizing Enzyme System No drug interactions of clinical importance have been identified.
- Finasteride does not appear to affect the cytochrome P450-linked drug metabolizing enzyme system.
- Compounds that have been tested in man have included antipyrine, digoxin, propranolol, theophylline, and warfarin and no clinically meaningful interactions were found. Other Concomitant Therapy Although specific interaction studies were not performed, PROSCAR was concomitantly used in clinical studies with acetaminophen, acetylsalicylic acid, α-blockers, angiotensin-converting enzyme (ACE)...
Pregnancy and breastfeeding
The opening of the pregnancy section of the label. The full section is longer and is in the source document.
Propecia
Pregnancy Category X. PROPECIA is contraindicated for use in women who are or may become pregnant. PROPECIA is a Type II 5α-reductase inhibitor that prevents conversion of testosterone to 5α-dihydrotestosterone (DHT), a hormone necessary for normal development of male genitalia.
Proscar
PROSCAR is contraindicated in pregnant females and not indicated for use in females. Based on animal studies and the mechanism of action, PROSCAR may cause abnormal development of external genitalia in a male fetus if administered to a pregnant female.
Generic or brand
Generic finasteride is approved and widely available in both the 1 mg and the 5 mg strength.
The FDA label database lists 12 approved generic applications for this ingredient.
What affects the cost
Finasteride has been generic for years, which puts it at the low end of the cost range in this category. This site sells nothing and links to no sellers.
What pharmacies pay for it
These are acquisition costs: what pharmacies in the United States pay on average to buy the medication, published weekly by the Centers for Medicare and Medicaid Services. They are not retail prices and not what a person pays at the counter, which depends on insurance, pharmacy and discount programmes. They are useful as an objective floor and for seeing how far a brand sits above its generic.
| Measured | Brand | Generic |
|---|---|---|
| per tablet, capsule or pen | Brand$4.84 (range $3.58 to $5.72, 120 listings) | Generic$0.069 (range $0.041 to $0.070, 1340 listings) |
Median of 1460 listings. Effective dates 2025-12-17 to 2026-07-22, file dated 2026-07-29.
Compared with other medications
What the labels do not do is compare one medication against another. These pages put two of them side by side.
Common questions
- Is finasteride approved for women?
- No. The Propecia label states that it is indicated in men only and is not indicated for use in women. It also contraindicates use in women who are or may become pregnant, and warns that women who are or may become pregnant should not handle crushed or broken tablets.
- What is the difference between Propecia and Proscar?
- The dose and the approved condition. Propecia is 1 mg and is approved for male pattern hair loss. Proscar is 5 mg and is approved for benign prostatic hyperplasia. Both labels are linked on this page.
- How long does the label say it takes to see an effect?
- The Propecia label states that in general, daily use for three months or more is necessary before benefit is observed, and that continued use is recommended to sustain benefit.
Other medications under hair loss
Whether each one carries an FDA approval for this use is marked on its page and in this list.
Sources
Every fact above comes from one of these documents. The date is the effective date of the label version this page was built from.
FDA prescribing information for Propecia
Organon LLC. Label version 9, effective 14 October 2024.
FDA prescribing information for Proscar
Organon LLC. Label version 9, effective 18 March 2026.
Each stripe is one section of the label, each division in a stripe one entry in that section.
Page last updated 18 August 2026
Compiled by the HealthyStudy editorial team from FDA source documents. No medical reviewer is credited on this page, because none reviewed it.