Finasteride

Finasteride is an oral type-II 5-alpha-reductase inhibitor with an FDA-approved male-pattern-hair-loss indication in men and large randomized hair-count trials.

tier S · skin · +107 hairs placebo-adjusted one-year vertex-area difference

verdict

Oral finasteride 1 mg slows progression and improves measured scalp-hair outcomes in men with androgenetic alopecia while treatment continues. That record does not transfer to compounded topical products, women, children, or every pattern of hair loss.

the core tension

Finasteride has mature oral hair-loss evidence, but DHT suppression is systemic, not a scalp-only effect. The benefit has to be weighed against the controlled-trial and label safety record, while postmarketing events retain their unknown-frequency and unknown-causality qualifiers. The evidence still must not be broadened to other populations, hair patterns, doses, or topical compounds.

what it is

Finasteride is a selective type-II 5-alpha-reductase inhibitor. Propecia is the 1-mg oral hair-loss product; Proscar is a separate 5-mg oral BPH product.

what it does

It reduces conversion of testosterone to dihydrotestosterone in scalp and systemic compartments; this is not a hair-selective mechanism. A 42-day scalp-biopsy study measured large scalp and serum DHT reductions, but that mechanistic dose response does not prove better hair outcomes or safety at higher doses.

origin

The reviewed US Propecia label covers oral treatment of male pattern hair loss in men only. Efficacy for bitemporal recession is not established, and topical compounds do not inherit the oral approval or PK record.

does it work

Two randomized trials in 1,553 men found a placebo-adjusted difference of 107 hairs in the measured vertex area after one year and 138 after two years among the blinded continuation record, with concordant patient, investigator, and photographic assessments.

key facts

• molecular formula: C23H36N2O2
• molecular weight: 372.545 g/mol
• amino acids: n/a (steroidal small molecule, not a peptide)
• half-life: about 5 to 6 h in adults aged 18 to 60 after oral tablets; longer in older adults
• type: selective type-II 5-alpha-reductase inhibitor
• CAS: 98319-26-7
• 1,553 men in the two one-year efficacy trials
• +107 placebo-adjusted hairs in the measured area at year one
• +138 placebo-adjusted hairs at year two

frequently asked questions

Is finasteride FDA approved for hair loss?

Yes. The reviewed Propecia label covers oral 1-mg finasteride for male pattern hair loss in men only.

Does that approval cover topical finasteride?

No. A compounded topical product has a different formulation and exposure and does not inherit Propecia's approval, efficacy, PK, or safety record.

Does it work at the frontal hairline?

The label says efficacy in bitemporal recession has not been established. The pivotal trials chiefly measured a defined vertex area and broader assessments.

What is the oral half-life?

The label reports about 5 to 6 hours in adults aged 18 to 60, with longer values in older adults. That oral-tablet number does not describe a topical compound.

Do postmarketing reports give a risk percentage?

No. The label lists reported events, including persistent sexual dysfunction and mood-related events, but spontaneous reports cannot provide incidence or prove causality.

What can systemic DHT blocking with finasteride affect?

Blocking DHT is not scalp-only. In the year-one hair trials, decreased libido was 1.8% with Propecia versus 1.3% with placebo, erectile dysfunction 1.3% versus 0.7%, and ejaculation disorder 1.2% versus 0.7%; at least one of those sexual events occurred in 3.8% versus 2.1%. The label also records voluntary postmarketing reports of sexual dysfunction that continued after discontinuation, infertility or poor seminal quality, breast tenderness or enlargement, depression, and suicidal ideation or behavior; those reports cannot estimate frequency or prove causality. PSA interpretation, pregnancy handling, and a 5-mg prevention-trial high-grade signal at five times the Propecia dose, with unknown significance for 1-mg users, are separate label concerns.

related peptides

• Dutasteride: The finasteride evidence cited on this page does not establish dutasteride's mechanism, approval, or outcomes.
• Minoxidil: The finasteride evidence cited on this page does not establish minoxidil's route, mechanism, approval, or outcomes.

reptides grades the research record and cites the literature behind every call. research reference only; not medical advice.