Finasteride 5 mg (Proscar): Dosage, Cost, and What It Treats

Finasteride 5 mg is the original FDA-approved formulation of finasteride, approved in 1992 for benign prostatic hyperplasia (BPH). Sold under the brand name Proscar (Merck) and widely available as generic finasteride 5 mg, it is indicated for symptomatic BPH in men with an enlarged prostate to: improve urinary symptoms, reduce acute urinary retention risk, and reduce the need for BPH-related surgery. The 5 mg dose was preceded by the 1 mg dose (Propecia for AGA, 1997) only in timing of AGA indication; the 5 mg formulation came first.

Key Dosage Facts

Parameter	Details
Approved dose	5 mg orally once daily
Administration	With or without food
Indication	Symptomatic BPH (men); not approved for women or AGA
Minimum assessment time	6 months before evaluating urinary symptom response
Duration of treatment	Indefinite; prostate re-enlarges after stopping
Brand name	Proscar (Merck)
Generic availability	Yes — therapeutically equivalent
Approximate monthly cost (generic)	$20–$40
Approximate monthly cost (brand Proscar)	$100–$150+

When Is 5 mg Used for Hair Loss?

Finasteride 5 mg is sometimes used off-label by men who cut the tablets into quarters (approximately 1.25 mg/quarter) as a cost-saving strategy — generic 5 mg tablets are often substantially cheaper per milligram than 1 mg tablets. While this is off-label and the tablets are not scored for splitting, the pharmacokinetics support equivalence since both 1 mg and 1.25 mg sit at the plateau of the dose-response curve for DHT suppression.

Finasteride 5 mg is not approved for hair loss, and using it that way requires a physician discussion. Women must never handle cut or crushed finasteride tablets due to the teratogenicity risk.

PSA Monitoring Is Essential at 5 mg

Finasteride 5 mg reduces serum PSA by approximately 50%. Men on finasteride 5 mg for BPH must inform all treating physicians about their finasteride use. PSA values must be doubled when interpreting cancer screening results. AUA BPH guidelines recommend a baseline PSA before starting finasteride and at 6 months to confirm the expected suppression; any PSA increase on finasteride warrants evaluation.

Response Timeline for BPH

• 1–3 months: DHT suppressed; prostate begins to shrink; most patients see no symptom change yet
• 3–6 months: Urinary flow (Q_max) and symptom scores (IPSS/AUA-SI) begin to improve
• 6–12 months: Full benefit typically established; maximum prostate shrinkage achieved
• 4+ years: Ongoing risk reduction in acute urinary retention (57% reduction vs. placebo in PLESS) and BPH surgery (55% reduction)

See: Full guide: Finasteride for BPH | Finasteride 1 mg for hair loss

Sources

• Merck & Co. Proscar (finasteride 5 mg) US Prescribing Information. Revised 2022.
• McConnell JD, et al. “The effect of finasteride on the risk of acute urinary retention and the need for surgical treatment.” N Engl J Med. 1998;338:557–563.