Propecia (Finasteride) 1 mg / Proscar 5 mg Tablets: Prescription 5-Alpha Reductase Inhibitor for Male Pattern Baldness and Benign Prostatic Hyperplasia

Reviewed by the Lucas Clinic Medical Team | Updated May 2026

Finasteride is a synthetic 4-azasteroid compound — a specific Type II 5-alpha reductase inhibitor (5-ARI). It works by inhibiting the enzyme 5-alpha reductase type II, which converts testosterone to dihydrotestosterone (DHT) in tissues including the prostate, scalp, and skin. DHT is a potent androgen — approximately 5-fold more potent than testosterone at androgen receptors — responsible for driving prostate growth in BPH and miniaturising hair follicles in androgenetic alopecia (male pattern hair loss, MPHL). By reducing DHT production by approximately 65–70%, finasteride addresses the hormonal driver of both conditions.

Finasteride is marketed in two doses for two different indications — a distinction that sometimes confuses patients. Propecia (1 mg finasteride) is approved for male pattern baldness (androgenetic alopecia) in men only. Proscar (5 mg finasteride) is approved for BPH symptoms and BPH-related complications (urinary retention, surgery risk reduction). Both are the same active ingredient at different doses, and generic finasteride is available in both 1 mg and 5 mg strengths. Both are prescription-only, both require continuous daily use to maintain effect, and both carry the same teratogenicity risk and the same sexual side effect profile — though at slightly different frequencies at the two dose levels.

What Is Propecia / Proscar (Finasteride)?

Finasteride's inhibition of 5-alpha reductase type II selectively reduces DHT at target tissues. In the prostate (BPH indication — Proscar 5 mg): reduces prostate volume by approximately 20–30% over 6–12 months; reduces risk of acute urinary retention by approximately 57% and need for BPH-related surgery by approximately 55% over 4 years (PLESS trial). Symptom improvement in BPH is more gradual than alpha blockers — full benefit takes 6–12 months. In the scalp (male pattern hair loss — Propecia 1 mg): slows hair loss progression in 83% of men and stimulates visible regrowth (primarily vertex, less so frontal) in approximately 66% at two years; continuous use is required or regained hair is lost within 6–12 months of stopping. Effects in both indications reverse on discontinuation.

Teratogenicity warning: Finasteride is a known teratogen for male fetuses — it can cause abnormal development of external genitalia (hypospadias, ambiguous genitalia) in male fetuses exposed in utero during first trimester organogenesis. Pregnant women or women who may become pregnant must not: handle finasteride tablets that are crushed, broken, or chewed (intact film-coated tablets do not pose risk as long as exposure to the active drug is prevented). Male patients taking finasteride should ensure tablets are kept away from pregnant female partners. Partners who are pregnant should not handle finasteride in any form that might allow skin contact with the active ingredient.

Prescription vs. Over-the-Counter Status

Both Propecia (1 mg) and Proscar (5 mg) are prescription-only in the US and UK. However, in the UK since 2019, finasteride 1 mg has been reclassified for pharmacy-only supply ("P" status) via a pharmacist consultation for male pattern hair loss — making it available without a GP prescription from UK pharmacies following a structured pharmacist consultation (excluding women and those under 18). In the US and most other markets, a prescription remains required. Telehealth platforms (Keeps, Hims, Roman) commonly facilitate online prescriptions for finasteride 1 mg for hair loss.

Available Strengths and Forms

Finasteride is available as film-coated tablets in two standard doses: 1 mg (Propecia — for male androgenetic alopecia) and 5 mg (Proscar — for BPH). Both are taken once daily, with or without food, at the same time each day. Some patients on Proscar split 5 mg tablets to obtain 1.25 mg doses for hair loss — this is sometimes recommended by hair loss specialists as a cost-reducing strategy, but note that splitting or cutting finasteride tablets removes the film coating and creates dust exposure risk — women of childbearing potential must not handle tablet fragments. Generic finasteride 1 mg and 5 mg tablets are widely available in the US at significantly lower cost than branded Propecia or Proscar.

Price of Propecia / Finasteride

Branded Propecia 1 mg (30 tablets) retails for approximately $60–$100/month at US pharmacies. Generic finasteride 1 mg is substantially less expensive: approximately $10–$25 per month with GoodRx, or via telehealth platforms. The Proscar 5 mg (splitting approach) reduces cost further. Generic finasteride 5 mg (30 tablets / one month at 5 mg BPH dose) costs approximately $10–$20 without insurance. In the UK, finasteride 1 mg can be purchased from a pharmacy following a P-category consultation for approximately £10–£20/month. Manufacturer coupons for Propecia are occasionally available via Merck's patient assistance programme. Long-term treatment requires ongoing cost planning given indefinite daily use for hair loss.

Frequently Asked Questions

How long does finasteride take to work for hair loss?

It typically takes 3–6 months of continuous daily use before any visible improvement is seen in hair loss with finasteride 1 mg. The first 3 months often involve increased shedding as the hair growth cycle synchronises — this is normal and not a sign of treatment failure. Visible regrowth, particularly at the vertex, becomes more apparent at 12 months and the maximum benefit is typically seen at 2 years. It is critical to continue taking finasteride daily without interruption to maintain results. Stopping finasteride leads to return of progressive hair loss — any regrowth achieved is lost within 6–12 months of discontinuation.

What is post-finasteride syndrome?

Post-finasteride syndrome (PFS) is a controversial condition described by some men as persistent sexual, neurological, and psychological side effects (erectile dysfunction, reduced libido, ejaculatory dysfunction, depression, cognitive impairment) continuing after cessation of finasteride. The Post-Finasteride Syndrome Foundation has advocated for research into this reported phenomenon. The clinical evidence is mixed: regulatory agencies including the FDA have added label warnings for persistent sexual side effects. The underlying mechanism is not established. The prevalence of PFS as a distinct, persistent syndrome (as opposed to the expected resolution of side effects after stopping) remains debated in the medical literature. Prescribers should counsel patients about the potential for sexual side effects and the possibility of persistence — informed consent is important before initiating therapy.

Does finasteride increase the risk of prostate cancer?

Finasteride significantly reduces PSA levels (by approximately 50% after 6 months), which must be accounted for when interpreting PSA screening results — a patient's PSA on finasteride should be doubled to estimate the equivalent un-treated PSA level. The PCPT (Prostate Cancer Prevention Trial) demonstrated that finasteride reduced prostate cancer prevalence by 25% — but with a small increase in the detection of high-grade (Gleason 7+) cancers, which is now generally attributed to detection bias from improved sampling of smaller prostates rather than a true biological increase in high-grade cancer. Current FDA position and clinical consensus is that finasteride does not increase the absolute risk of high-grade prostate cancer. Men should continue regular PSA monitoring with dose-adjusted interpretation of results while on finasteride.

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