What is Finasteride used for?

Finasteride is evaluated for the following indications with varying evidence strength: Androgenetic alopecia (evidence tier A), Benign prostatic hyperplasia (evidence tier A), Anti-aging and longevity (evidence tier F). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Finasteride?

Common side effects of Finasteride (≥ 1 in 100): Decreased libido (3-5%), Erectile dysfunction (3-5%), Decreased ejaculate volume, Gynaecomastia, Rash, pruritus. See the Safety section for uncommon and serious reactions.

Who should not take Finasteride?

Finasteride is contraindicated in: Pregnancy (category X); Age under 18; Hypersensitivity; Women of childbearing age (without contraception). Full list in the Safety section.

Finasteride 1 mg/day is first-line therapy for male androgenetic alopecia. Kaufman 1998 RCT (n=1879, 2 years) showed 86 hairs/cm² increase in vertex hair count, with sustained results during continued use. Effect plateaus by 12 months and persists only with continuous use – discontinuation leads to renewed hair loss. The drug is not approved in premenopausal women. Post-finasteride syndrome (PFS) – persistent sexual, cognitive, and emotional symptoms after discontinuation – has been reported in a small subgroup; incidence and causality remain debated. and BAD guidelines list finasteride as first-line for male androgenetic alopecia.

Benign prostatic hyperplasia

First line

Finasteride 5 mg/day is evidence-based first-line therapy for benign prostatic hyperplasia with prostate volume above 30-40 mL. The PLESS trial (Roehrborn 2002, n=3040, 4 years) showed 57% reduction in acute urinary retention risk and 55% reduction in surgery need versus placebo. Prostate volume shrinks by 20-25%, PSA by about 50% (important for prostate cancer screening interpretation). Effect develops over 6-12 months. Combination with α-blockers (tamsulosin, doxazosin) provides additional benefit on symptoms and progression risk (MTOPS, CombAT). AUA, EAU, and guidelines list finasteride as first-line for obstructive BPH with enlarged prostate.

Sources

Anti-aging and longevity

Not recommended

Finasteride is a type II 5α-reductase inhibitor. It is prescribed for men with benign prostatic hyperplasia and androgenic alopecia; it is not indicated in women (AEMPS Ficha Técnica). Finasteride is prescribed to women of reproductive age for hair loss off-label and in anti-aging protocols. In women, clinical evidence for hair loss is insufficient, and the drug is teratogenic ( category X, risk of male fetal external genitalia development disruption – contact even through skin is contraindicated with broken tablets). In men, finasteride can cause reduced libido, erectile dysfunction, depression, and gynecomastia; a post-finasteride syndrome with prolonged adverse effects after discontinuation has been described. If finasteride was prescribed to a woman of reproductive age or to a man without confirmed indications, consider seeking a second opinion.

Sources

Russian practice note

In Russia, finasteride is registered as 5 mg (Proscar, generics) for BPH and 1 mg (Propecia) for alopecia. Generic 5 mg formulations cost 400-800 ₽/month. The 1 mg dose for alopecia is often obtained by splitting 5 mg tablets (off-label practice, not regulator-prohibited but not recommended by the manufacturer due to uneven active ingredient distribution). Finasteride lowers PSA by approximately half – measured PSA must be doubled when interpreting prostate cancer screening. Pregnancy category X: handling crushed tablets is contraindicated for pregnant women (risk of hypospadias in the male fetus).

Drug interactions

Clinically significant drug interactions are uncommon. Metabolised via CYP3A4, but at therapeutic doses does not affect concentrations of warfarin, digoxin, theophylline, or antipyrine. Combination with α-blockers (CombAT) enhances overall effect on BPH symptoms.

Contraindications

Pregnancy (category X)
Age under 18
Hypersensitivity
Women of childbearing age (without contraception)

Serious adverse effects

Post-finasteride syndrome (PFS) – persistent sexual, cognitive, and emotional symptoms after discontinuation
Depression and suicidal ideation (rare reports)
Male breast cancer (rare)

Common adverse effects

Decreased libido (3-5%)
Erectile dysfunction (3-5%)
Decreased ejaculate volume
Gynaecomastia
Rash, pruritus

PregnancyFDA X

Category X. Contraindicated in pregnant women, including handling of crushed tablets, due to risk of male fetal hypospadias.

Breastfeeding

The drug is not intended for women; if treatment is required, breastfeeding should be discontinued.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Finasteride

Mechanism of action

Indications

Androgenetic alopecia

Benign prostatic hyperplasia

Marketing claims without evidence base

Anti-aging and longevity

Practical notes

Russian practice note

Drug interactions

Check interaction with another drug

Official sources

Safety