Does the effect stop when the tablet stops?

The label addresses this directly: the effect is maintained by continued use. What the treatment holds is held only while it is taken.

Why is a prostate medicine on a hair loss page?

Because 1 mg and 5 mg finasteride are the same substance under two approvals. Both labels are shown here so it is clear which strength was approved for which condition.

Why does the label warn about pregnancy when men take it?

Because of what the substance does to a developing male foetus, which is why the label restricts handling of the tablets by anyone who is or may become pregnant. The exact wording is in the label section above.

Finasteride

A daily tablet approved for male pattern hair loss at 1 mg, and for the prostate at 5 mg, which is the same substance in a five times larger dose.

Class: 5-alpha reductase inhibitor
Sold as: Sold as: Propecia, Proscar; Prescription only

From the approved label

Propecia

Approved uses: PROPECIA is a 5α-reductase inhibitor indicated for the treatment of male pattern hair loss (androgenetic alopecia) in MEN ONLY.
Efficacy in bitemporal recession has not been established.
PROPECIA is not indicated for use in women.
Forms and strengths: 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.
How it is taken: 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.
Must not be used when: 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.
Interactions: 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,...
Warnings and precautions: 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.
Common side effects: 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.
Pregnancy: 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.
How it acts: 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.

Label holder:: Organon LLC
Label version:: 14 October 2024

This section reports the approved product information. The wording is condensed from the regulator's own summary, and the full document is linked under Sources.

Written by us

How it works

Finasteride blocks the enzyme that converts testosterone into dihydrotestosterone, the hormone that shrinks hair follicles in pattern hair loss. Less of that hormone reaching the follicle slows the process and, in part of the scalp, reverses it. It is not a treatment applied to hair, it is a hormonal treatment taken as a tablet, and that distinction explains both its effect and its warnings.

Original and generic

Both strengths are off patent and generic finasteride is what pharmacies dispense by default. The 1 mg and 5 mg tablets contain the same substance, and the reason the label for each is different is that they were approved for different conditions on different evidence.

What it costs

One of the cheapest ongoing prescription treatments in this catalogue. Generic finasteride at 1 mg costs a few euros for a month's supply at European pharmacy prices, and most of what an online clinic charges is the consultation and the delivery, not the tablet.

How to get it legally

Prescription only in the European Union, the United Kingdom and the United States. An online consultation is the normal route, and the questions that matter are about planning a pregnancy in the household, mood history and prostate testing, because those are the three areas where the label has something to say.

From the approved label

Proscar: approved for

Approved uses: 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: 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 it is taken: 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.
Must not be used when: 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.
Interactions: 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)...
Warnings and precautions: 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.
Common side effects: 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.
Pregnancy: 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.
How it acts: The development and enlargement of the prostate gland is dependent on the potent androgen, 5α-dihydrotestosterone (DHT). Type II 5α-reductase metabolizes testosterone to DHT in the prostate gland, liver and skin. DHT induces androgenic effects by binding to androgen receptors in the cell nuclei of these organs.

Label holder:: Organon LLC
Label version:: 18 March 2026

This section reports the approved product information. The wording is condensed from the regulator's own summary, and the full document is linked under Sources.

Comparison

Questions

Does the effect stop when the tablet stops?: The label addresses this directly: the effect is maintained by continued use. What the treatment holds is held only while it is taken.
Why is a prostate medicine on a hair loss page?: Because 1 mg and 5 mg finasteride are the same substance under two approvals. Both labels are shown here so it is clear which strength was approved for which condition.
Why does the label warn about pregnancy when men take it?: Because of what the substance does to a developing male foetus, which is why the label restricts handling of the tablets by anyone who is or may become pregnant. The exact wording is in the label section above.

Sources

PROPECIA: prescribing informationDailyMed, US National Library of Medicine. Label version 14 October 2024
PROSCAR: prescribing informationDailyMed, US National Library of Medicine. Label version 18 March 2026
Drugs@FDA: NDA020788US Food and Drug Administration
Drugs@FDA: NDA020180US Food and Drug Administration