Encyclopedia · antiandrogen
Finasteride
A prescription pill (and in some countries a scalp spray) that lowers DHT and is the best-proven drug for stopping male pattern hair loss.
What it is
Finasteride blocks type 2 5-alpha-reductase, the enzyme that turns testosterone into DHT. The 1 mg tablet (Propecia and generics) is approved for male pattern hair loss; the 5 mg tablet (Proscar) is for an enlarged prostate. Kaufman 1998
Where it stands as of 10 October 2026:
- US: the 1 mg tablet is approved for men and is prescription-only. No topical finasteride is FDA-approved. Compounded topical products sold through telehealth are unapproved, and the FDA issued an alert about them on 22 April 2025. FDA 2025
- EU: the 1 mg tablet is authorised for men aged 18 to 41 with early hair loss, and a finasteride skin spray is authorised in some member states. Belgium never approved the 1 mg tablet. EMA 2025; CMDh 2025
- UK: the 1 mg tablet is prescription-only, and the MHRA added a patient alert card in 2024. MHRA 2024
- Women: not approved anywhere we checked, and it is contraindicated in pregnancy because it can feminise a male fetus. Propecia label
How it works
DHT is the androgen that shrinks susceptible scalp follicles over successive hair cycles (see DHT and pattern hair loss). Finasteride cuts DHT production without lowering testosterone, which is why it is not a "testosterone blocker".
- Bald scalp held more DHT than hairy scalp in the same men (7.37 vs 4.20 pmol/g). Finasteride 5 mg for 28 days brought bald-scalp DHT down from 6.40 to 3.62 pmol/g, about the level of hair-bearing scalp, and testosterone did not fall. Dallob 1994
- Finasteride blocks the type 2 enzyme. Type 1 is the predominant 5-alpha-reductase in scalp overall, but immunostaining of scalp from men with pattern loss placed type 2 in the outer and inner root sheath of the follicle, with type 1 in sebaceous glands and not in the follicle (Bayne 1999, authors at the manufacturer). Cultured papilla cells, by contrast, expressed mostly type 1, highest in beard cells (Liu 2008). That conflict is part of the case for dual inhibitors.
- In prostate patients, finasteride 5 mg lowered serum DHT by 70.8% against 94.7 to 98.4% for dutasteride 0.5 to 5 mg, so a fair share of DHT is left under finasteride (Clark 2004).
- In 249 men, scalp DHT fell 13.0% on placebo vs 56.5% (0.2 mg), 64.1% (1 mg) and 69.4% (5 mg) after 42 days. Even 0.2 mg nearly maxes out the effect. Drake 1999
What the studies show
- Pivotal trials (1,553 men, ages 18 to 41): about 107 more hairs than placebo at 1 year and 138 more at 2 years in a 5.1 cm² vertex circle (baseline about 876), while the placebo group kept losing hair. Kaufman 1998
- Five years: the improvement held over 5 years in controlled extensions, with no new safety signals. Study Group 2002
- What untreated looks like: men on placebo lost 239 hairs (26.3% of density) in the target area over 5 years, and 75% looked worse on photos. Kaufman 2008
- Meta-analysis (3,927 men, 12 trials): about 1 in 5.6 men noticed improvement over placebo within a year, and 1 in 3.4 after two years or more. Hair count rose 9.4% (short term) and 24.3% (long term) more than placebo. Mella 2010
- Frontal scalp: a 1-year trial found a significant hair-count gain in the frontal and mid scalp. Leyden 1999 Even so, the EU product information says efficacy in temple recession and end-stage loss is not established. CMDh 2025
- Japanese men (414): photos improved in 58% on 1 mg, 54% on 0.2 mg and 6% on placebo over 48 weeks. Kawashima 2004
- Identical twins: the twin on finasteride had visibly more hair than the twin on placebo after a year. Stough 2002
- Around a transplant (79 men): visible frontal improvement in 94% on finasteride vs 67% on placebo at 48 weeks. Leavitt 2005
- 10-year follow-up (118 men, uncontrolled): benefit was maintained, men over 30 responded better, and 42.8% of men aged 20 to 30 had not improved by year 10. Rossi 2011
- Topical spray (458 men, 24 weeks): about 20.2 more hairs than placebo's 6.7, numerically similar to the pill, with plasma finasteride over 100 times lower. Serum DHT still fell 34.5% (topical) vs 55.6% (oral). Piraccini 2022 A Chinese phase 3 (270 men) also beat placebo at 24 weeks. Zhou 2025
- Topical, real world (146 men, 52 weeks): +22.7 hairs/cm² at the vertex and +32.3 at the frontotemporal area; 6.2% had mild irritation. Piraccini 2026
- Women, 1 mg: no benefit over placebo in 137 postmenopausal women over 1 year. Price 2000 Uncontrolled studies at higher doses report gains, for example density 90 to 107 hairs/cm² at 12 months on 5 mg in 87 women. Yeon 2011 Reviews call the female evidence promising but low quality. Hu 2019; Nobari 2023
How it's used in studies
- Men, oral: 1 mg once daily; benefit was visible by 3 to 12 months. 0.2 mg also worked but slightly less well than 1 mg. Roberts 1999
- Men, topical: a 0.25% solution sprayed once daily. Small volumes (100 to 200 microlitres) cut scalp DHT by about 47 to 52% and serum DHT by 24 to 26%; larger volumes cut serum DHT 44 to 48%, so topical is not systemically inert. Caserini 2016 In Chinese men, steady-state plasma finasteride peaked at about 30 pg/mL. Tai 2025
- Women (off-label, outside trials of 1 mg): studies used 5 mg Oliveira-Soares 2013, 2.5 mg Won 2018, and 2.5 mg with a drospirenone pill (62% improved, 37 women). Iorizzo 2006
- With hair transplants: started 4 weeks before surgery and continued. Leavitt 2005
- Stopping: gains are lost after stopping because the underlying process continues. Kaufman 2008
Side effects and safety
Sexual side effects. In year 1 of the label trials, decreased libido was 1.8% vs 1.3% on placebo, erectile dysfunction 1.3% vs 0.7%, and ejaculation disorder 1.2% vs 0.7%. Propecia label A meta-analysis of 15 trials (4,495 men) found a raised risk (relative risk 1.66, 95% CI 1.20 to 2.30). Lee 2019 Trial safety reporting was poor: none of 34 trials reported adverse events adequately, and 56% were manufacturer-funded. Belknap 2015
The nocebo effect is large. In a blinded trial of finasteride 5 mg, men told about sexual side effects reported them far more often (43.6% vs 15.3%). Mondaini 2007 In the large Prostate Cancer Prevention Trial, finasteride raised sexual dysfunction scores only slightly and the gap shrank over time. Moinpour 2007
Mood and suicidality.
- Drug-safety databases show disproportionate reports of suicidality and depression, concentrated in men under 45 using it for hair loss and rising sharply after 2012, which partly reflects stimulated reporting. Nguyen 2021; Lee 2025; Gupta 2025
- Large cohorts, mostly older men with prostate disease, find more depression but no rise in suicide: Ontario self-harm hazard ratio 1.88, depression 1.94, suicide 0.88 Welk 2017; Sweden depression 1.61, suicide not associated. Garcia-Argibay 2022 A UK Biobank analysis found no association. Wang 2025
- Regulators now list suicidal ideation as a side effect. The EMA confirmed it on 8 May 2025 for finasteride tablets (frequency unknown), advised 1 mg users with mood changes to stop and seek advice, added a patient card, and found no link for the skin spray. Belgian and French members dissented, arguing the benefit-risk of 1 mg for hair loss is negative. EMA 2025; CMDh 2025 The MHRA added a patient alert card in April 2024 after 281 mood-related and 426 sexual-dysfunction reports. MHRA 2024 The US label lists post-marketing depression, suicidal ideation and sexual dysfunction that continued after stopping. Propecia label
- Whether some men develop lasting symptoms after stopping is covered in post-finasteride syndrome. The largest placebo-controlled follow-up (267,983 person-years) found no excess of 22 related conditions, but those men were 55 or older and took 5 mg. Till 2026
Topical finasteride. In the phase 3 trial adverse events did not differ meaningfully from placebo. Piraccini 2022 Drug-safety reports show fewer post-finasteride-type signals for topical than oral use. Gupta 2026 But serum DHT still falls by about a third, and the FDA's 2025 alert cites 32 reports for compounded topicals, including erectile dysfunction, suicidal ideation and depression that mostly persisted after stopping, plus skin irritation and a risk of transfer to women. FDA 2025 A telehealth company's records of 638,629 men on compounded topical finasteride (usually with minoxidil) showed side effects in 2.7% of the 23.7% who answered a follow-up; the data were uncontrolled and company-run. Yu 2026
Fertility. Finasteride 1 mg for 48 weeks did not change sperm count, motility or morphology in young men. Overstreet 1999 At 5 mg, total sperm count fell about 34% at 26 weeks and recovered. Amory 2007 In 27 subfertile men already on finasteride, sperm counts rose on average 11.6-fold after stopping. Samplaski 2013 Men with low sperm counts or who are trying to conceive should raise this with a doctor.
Prostate and PSA. Finasteride lowers PSA (1 mg: mean 0.7 to 0.5 ng/mL at 12 months), so a PSA test must be read knowing you take it. The label also carries a class warning about high-grade prostate cancer. Propecia label In the prevention trial (5 mg), prostate cancer diagnoses fell about 30% (relative risk 0.70), high-grade cancer was slightly more common (1.17), and survival was identical. Thompson 2013 In men taking 1 mg for hair loss, long-term use was linked to fewer BPH and prostate cancer diagnoses in a 2026 claims study. Adler 2026 In another 2026 matched cohort, erectile dysfunction diagnoses did not differ, though users more often received PDE5 inhibitor prescriptions (13.6% vs 10.5%). Xu 2026
Pregnancy. Women who are or may be pregnant should not handle crushed or broken tablets. Propecia label Topical products add a skin-transfer route. FDA 2025
Bottom line
Finasteride is the reference drug for slowing male pattern hair loss. It suits men with early-to-moderate loss at the crown or mid-scalp who want to keep what they have. Most untreated men keep losing hair, and roughly 1 in 3 to 6 notice improvement over placebo. Expect realistic results at the temples, where evidence is weaker.
Before starting, know the points regulators highlight: a mood warning (if your mood drops on the 1 mg tablet, stop and get help), uncommon and usually reversible sexual side effects, an effect on PSA tests, care around pregnancy, and the fact that gains fade if you stop. The generic 1 mg tablet is the budget option; the spray lowers blood levels but is not proven safer. In women it is not a first-line choice, and the doses studied for them rest on uncontrolled data. Discuss with a doctor.
Fun facts
- The 1 mg hair dose was chosen after 0.01 mg did nothing and 0.2 mg already suppressed most scalp DHT. Roberts 1999; Drake 1999
- In a twin trial, one identical twin took finasteride and the other placebo; after a year the treated twins visibly had more hair. Stough 2002
- The 5 mg prostate dose, given to thousands of older men, cut prostate cancer diagnoses by about 30%. Thompson 2013
Studies 51
Kaufman KD et al. Finasteride in the treatment of men with androgenetic alopecia. J Am Acad Dermatol. 1998
Tested: finasteride 1 mg/day vs placebo
Result: Finasteride grew about 107 more hairs than placebo at 1 year and about 138 more at 2 years in a 5.1 cm2 vertex circle (baseline about 876); placebo men kept losing hair.
Read the study ↗Finasteride Male Pattern Hair Loss Study Group. Long-term (5-year) multinational experience with finasteride 1 mg in the treatment of men with androgenetic alopecia. Eur J Dermatol. 2002
Tested: finasteride 1 mg/day vs placebo
Result: Hair improvement was maintained over 5 years while placebo men progressively lost hair; no new safety signals.
Read the study ↗Kaufman KD et al. Progression of hair loss in men with androgenetic alopecia (male pattern hair loss): long-term (5-year) controlled observational data in placebo-treated patients. Eur J Dermatol. 2008
Tested: no treatment (placebo)
Result: Untreated men lost about 239 hairs (26.3% of density) in the target area over 5 years, and 75% looked worse on photos.
Read the study ↗Roberts JL et al. Clinical dose ranging studies with finasteride, a type 2 5alpha-reductase inhibitor, in men with male pattern hair loss. J Am Acad Dermatol. 1999
Tested: finasteride 0.01, 0.2, 1 and 5 mg/day
Result: 0.2 mg and above worked, 1 mg and 5 mg were similar and better than 0.2 mg, and 0.01 mg was no better than placebo.
Read the study ↗Drake L et al. The effects of finasteride on scalp skin and serum androgen levels in men with androgenetic alopecia. J Am Acad Dermatol. 1999
Tested: finasteride 0.2, 1 or 5 mg/day vs placebo
Result: Scalp DHT fell 13.0% on placebo vs 56.5% (0.2 mg), 64.1% (1 mg) and 69.4% (5 mg); serum DHT fell about 69-72% at those doses.
Read the study ↗Dallob AL et al. The effect of finasteride, a 5 alpha-reductase inhibitor, on scalp skin testosterone and dihydrotestosterone concentrations in patients with male pattern baldness. J Clin Endocrinol Metab. 1994
Tested: finasteride 5 mg/day
Result: Bald scalp held more DHT than hairy scalp (7.37 vs 4.20 pmol/g); finasteride lowered bald-scalp DHT from 6.40 to 3.62 pmol/g without lowering testosterone.
Read the study ↗Show 45 more studies
Kawashima M et al. Finasteride in the treatment of Japanese men with male pattern hair loss. Eur J Dermatol. 2004
Tested: finasteride 1 mg or 0.2 mg/day vs placebo
Result: Photos improved in 58% (1 mg), 54% (0.2 mg) and 6% (placebo).
Read the study ↗Leyden J et al. Finasteride in the treatment of men with frontal male pattern hair loss. J Am Acad Dermatol. 1999
Tested: finasteride 1 mg/day vs placebo
Result: Hair counts rose significantly in the frontal (anterior and mid) scalp.
Read the study ↗Stough DB et al. Finasteride improves male pattern hair loss in a randomized study in identical twins. Eur J Dermatol. 2002
Tested: finasteride 1 mg/day in one twin, placebo in the other
Result: The treated twin had more hair than the placebo twin on photos and counts after 1 year.
Read the study ↗Leavitt M et al. Effects of finasteride (1 mg) on hair transplant. Dermatol Surg. 2005
Tested: finasteride 1 mg/day vs placebo
Result: Visible frontal improvement in 94% on finasteride vs 67% on placebo.
Read the study ↗Mella JM et al. Efficacy and safety of finasteride therapy for androgenetic alopecia: a systematic review. Arch Dermatol. 2010
Tested: finasteride vs placebo
Result: Number needed to treat was 5.6 (up to 12 months) and 3.4 (24 months or more) for self-perceived improvement; erectile dysfunction relative risk 2.22 (about 1 extra case per 82 men).
Read the study ↗Rossi A et al. Finasteride, 1 mg daily administration on male androgenetic alopecia in different age groups: 10-year follow-up. Dermatol Ther. 2011
Tested: finasteride 1 mg/day (uncontrolled)
Result: Benefit was maintained; men over 30 and with higher grades responded better; 42.8% of men aged 20-30 had not improved by 10 years; 6% reported side effects.
Read the study ↗Price VH et al. Lack of efficacy of finasteride in postmenopausal women with androgenetic alopecia. J Am Acad Dermatol. 2000
Tested: finasteride 1 mg/day vs placebo
Result: No benefit over placebo on any endpoint.
Read the study ↗Piraccini BM et al. Topical finasteride spray solution for male androgenetic alopecia: phase III randomized controlled trial. J Eur Acad Dermatol Venereol. 2022
Tested: topical finasteride vs oral finasteride vs placebo
Result: Topical gained about 20.2 hairs vs 6.7 for placebo, similar to oral; plasma finasteride was over 100 times lower; serum DHT fell 34.5% (topical) vs 55.6% (oral).
Read the study ↗Caserini M et al. Effects of a novel finasteride 0.25% topical solution on scalp and serum dihydrotestosterone in healthy men with androgenetic alopecia. Int J Clin Pharmacol Ther. 2016
Tested: finasteride 0.25% topical solution at different volumes
Result: 100-200 microlitres lowered scalp DHT by about 47-52% and serum DHT by 24-26%; larger volumes lowered serum DHT 44-48%.
Read the study ↗Zhou C et al. Topical finasteride spray in Chinese men with androgenetic alopecia: phase III randomized controlled trial. Chin Med J. 2025
Tested: topical finasteride spray vs placebo
Result: Hair count and terminal hair count were better than placebo at 24 weeks.
Read the study ↗Tai Z et al. Pharmacokinetics of topical finasteride 0.25% spray in Chinese men: phase I. Adv Ther. 2025
Tested: finasteride 0.25% spray
Result: Steady-state plasma finasteride peaked at about 30 pg/mL.
Read the study ↗Piraccini BM et al. Effectiveness and safety of topical finasteride for male androgenetic alopecia: real world data. Int J Dermatol. 2026
Tested: topical finasteride 0.25% monotherapy
Result: Hair density rose by 22.7 hairs/cm2 at the vertex and 32.3 at the frontotemporal area; 6.2% had mild local irritation.
Read the study ↗Yu J et al. Compounded topical finasteride via a national telehealth platform: retrospective analysis. JMIR Dermatol. 2026
Tested: compounded topical finasteride with minoxidil
Result: Side effects were reported by 2.7% of the 23.7% who answered a follow-up; uncontrolled and company-run.
Read the study ↗Hu AC et al. The efficacy and use of finasteride in women: a systematic review. Int J Dermatol. 2019
Tested: finasteride
Result: Evidence in women was promising but low quality.
Read the study ↗Nobari NN et al. Systematic review of oral or topical finasteride for women with androgenetic alopecia. Adv Clin Exp Med. 2023
Tested: oral or topical finasteride
Result: Evidence in women was promising but low quality.
Read the study ↗Yeon JH et al. 5 mg/day finasteride treatment for normoandrogenic Asian women with female pattern hair loss. J Eur Acad Dermatol Venereol. 2011
Tested: finasteride 5 mg/day (uncontrolled)
Result: Hair density rose from 90 to 107 hairs/cm2 at 12 months.
Read the study ↗Oliveira-Soares R et al. Finasteride 5 mg/day treatment of patterned hair loss in normo-androgenetic postmenopausal women. Int J Trichology. 2013
Tested: finasteride 5 mg/day (uncontrolled)
Result: Improvement was reported in an uncontrolled series.
Read the study ↗Won YY et al. Oral finasteride 2.5 mg/day in women with female pattern hair loss. Dermatol Ther. 2018
Tested: finasteride 2.5 mg/day (retrospective)
Result: Improvement was reported in a retrospective series.
Read the study ↗Iorizzo M et al. Finasteride treatment of female pattern hair loss. Arch Dermatol. 2006
Tested: finasteride 2.5 mg/day plus a drospirenone pill
Result: 62% improved in an uncontrolled series.
Read the study ↗Lee S et al. Adverse sexual effects of finasteride or dutasteride for male androgenetic alopecia: a systematic review and meta-analysis. Acta Derm Venereol. 2019
Tested: finasteride or dutasteride vs placebo
Result: Finasteride 1 mg raised sexual dysfunction risk (relative risk 1.66, 95% CI 1.20-2.30); dutasteride relative risk 1.37 was not statistically significant.
Read the study ↗Belknap SM et al. Adverse event reporting in clinical trials of finasteride for androgenic alopecia: a meta-analysis. JAMA Dermatol. 2015
Tested: review of adverse-event reporting
Result: None of 34 trials had adequate adverse-event reporting; 56% were manufacturer-funded.
Read the study ↗Mondaini N et al. Finasteride 5 mg and sexual side effects: how many of these are related to a nocebo phenomenon? J Sex Med. 2007
Tested: finasteride 5 mg, with or without being told about sexual side effects
Result: Men told about side effects reported sexual problems far more often (43.6% vs 15.3%).
Read the study ↗Moinpour CM et al. Longitudinal analysis of sexual function reported by men in the Prostate Cancer Prevention Trial. J Natl Cancer Inst. 2007
Tested: finasteride 5 mg/day vs placebo
Result: Finasteride raised sexual dysfunction scores only slightly, and the gap shrank over time.
Read the study ↗Nguyen DD et al. Investigation of suicidality and psychological adverse events in patients treated with finasteride. JAMA Dermatol. 2021
Tested: finasteride
Result: Reporting odds ratio for suicidality 1.63 overall, higher in men under 45 and in hair-loss users; reports rose sharply after 2012.
Read the study ↗Lee S et al. Signal detection between 5-alpha reductase inhibitors and suicidality and depression: international pharmacovigilance. Eur J Clin Pharmacol. 2025
Tested: finasteride and dutasteride
Result: Much stronger signal for finasteride (reporting odds ratio 7.28) than dutasteride; concentrated in young men.
Read the study ↗Gupta AK et al. Finasteride use: evaluation of depression and suicide risk (FAERS). J Cosmet Dermatol. 2025
Tested: finasteride
Result: No suicidality signal in 2006-2011 but signals in 2013-2018 and 2019-2023, pointing partly to stimulated reporting.
Read the study ↗Welk B et al. Association of suicidality and depression with 5-alpha-reductase inhibitors. JAMA Intern Med. 2017
Tested: 5-alpha-reductase inhibitors vs non-use
Result: Self-harm hazard ratio 1.88 and depression 1.94 in the first 18 months; suicide hazard ratio 0.88.
Read the study ↗Garcia-Argibay M et al. Association of 5-alpha-reductase inhibitors with dementia, depression, and suicide. JAMA Netw Open. 2022
Tested: 5-alpha-reductase inhibitors vs non-use
Result: Depression hazard ratio 1.61; suicide was not associated.
Read the study ↗Wang J et al. Finasteride use does not lead to depression or suicide: cohort and Mendelian randomization analysis. J Cosmet Dermatol. 2025
Tested: finasteride
Result: No association with depression or suicide.
Read the study ↗Gupta AK et al. Topical versus oral finasteride safety: FAERS pharmacovigilance. Int J Dermatol. 2026
Tested: topical vs oral finasteride
Result: Fewer post-finasteride-type reports for topical than oral finasteride.
Read the study ↗Overstreet JW et al. Chronic treatment with finasteride daily does not affect spermatogenesis or semen production in young men. J Urol. 1999
Tested: finasteride 1 mg/day vs placebo
Result: Sperm count, motility and morphology did not change.
Read the study ↗Amory JK et al. The effect of 5alpha-reductase inhibition with dutasteride and finasteride on semen parameters and serum hormones in healthy men. J Clin Endocrinol Metab. 2007
Tested: dutasteride 0.5 mg, finasteride 5 mg or placebo
Result: Serum DHT fell 94% on dutasteride vs 73% on finasteride; semen volume fell about 30% and total sperm count about 25-34%, with partial recovery after stopping.
Read the study ↗Samplaski MK et al. Finasteride use in the male infertility population: effects on semen parameters. Fertil Steril. 2013
Tested: stopping finasteride
Result: Sperm counts rose on average 11.6-fold after stopping.
Read the study ↗Thompson IM Jr et al. Long-term survival of participants in the Prostate Cancer Prevention Trial. N Engl J Med. 2013
Tested: finasteride 5 mg/day vs placebo
Result: Prostate cancer diagnoses fell about 30% (relative risk 0.70), high-grade cancer was slightly more common (1.17), and survival was identical.
Read the study ↗Adler R et al. BPH and prostate cancer risk with long-term low-dose finasteride in men with alopecia. Urology. 2026
Tested: long-term finasteride 1 mg
Result: Long-term use was linked to fewer BPH and prostate cancer diagnoses in a claims study.
Read the study ↗Xu P et al. Urologic impact of long-term finasteride 1 mg for androgenic alopecia: matched cohort. World J Urol. 2026
Tested: finasteride 1 mg
Result: Erectile dysfunction diagnoses did not differ, but users were more often prescribed PDE5 inhibitors (13.6% vs 10.5%).
Read the study ↗Till C et al. No evidence of post-finasteride syndrome in 267,983 person-years of follow-up in the Prostate Cancer Prevention Trial. Urology. 2026
Tested: finasteride 5 mg vs placebo
Result: No excess of 22 post-finasteride-type conditions over placebo.
Read the study ↗European Medicines Agency. Measures to minimise risk of suicidal thoughts with finasteride and dutasteride medicines (EMA/142716/2025). 8 May 2025
Tested: regulatory review
Result: Suicidal ideation was confirmed as a side effect of finasteride tablets (frequency unknown; 313 EudraVigilance cases against about 270 million patient-years); patient card added; no link found for the skin spray.
Read the study ↗CMDh members (Belgium, France). Divergent statement, finasteride- and dutasteride-containing medicinal products (EMEA/H/A-31/1539). 2025
Tested: regulatory dissent
Result: Belgian and French members judged the benefit-risk of finasteride 1 mg for hair loss negative and noted that efficacy in temple recession is not established.
Read the study ↗MHRA. Men on finasteride asked to stay vigilant for possible psychiatric and sexual side effects. 29 April 2024
Tested: regulatory alert
Result: Patient alert card added after 281 mood-related and 426 sexual-dysfunction reports; sexual problems have persisted in some men after stopping.
Read the study ↗US FDA. FDA alerts health care providers, compounders and consumers of potential risks associated with compounded topical finasteride products. 22 April 2025
Tested: regulatory alert
Result: 32 adverse-event reports (2019-2024) including erectile dysfunction, suicidal ideation and depression, mostly persisting after stopping; topical products carry a skin-transfer risk to others.
Read the study ↗Organon. PROPECIA (finasteride) prescribing information, revised 8/2022. DailyMed
Tested: finasteride 1 mg
Result: Year-1 trial rates: decreased libido 1.8% vs 1.3%, erectile dysfunction 1.3% vs 0.7%, ejaculation disorder 1.2% vs 0.7%; post-marketing reports include depression, suicidal ideation and sexual dysfunction that continued after stopping; lowers PSA.
Read the study ↗Bayne EK et al. Immunohistochemical localization of types 1 and 2 5-alpha-reductase in human scalp. Br J Dermatol. 1999
Result: Type 1 is the predominant scalp enzyme overall, but in men with androgenetic alopecia type 2 stained in the outer and inner root sheath and infundibulum of the follicle, while type 1 stained in sebaceous glands and not in the follicle. Merck authors.
Read the study ↗Liu S, Yamauchi H. Different patterns of 5-alpha-reductase expression, cellular distribution, and testosterone metabolism in human follicular dermal papilla cells. Biochem Biophys Res Commun. 2008
Result: Beard and scalp papilla cells expressed mostly type 1 5-alpha-reductase mRNA (highest in beard), with minimal type 2. Testosterone was converted mainly to androstenedione and only a little DHT, and a type 1 inhibitor beat finasteride in beard papilla cells.
Read the study ↗Clark RV et al. Marked suppression of dihydrotestosterone in men with benign prostatic hyperplasia by dutasteride, a dual 5-alpha-reductase inhibitor. J Clin Endocrinol Metab. 2004
Tested: dutasteride 0.01 to 5 mg, finasteride 5 mg or placebo daily
Result: Serum DHT fell 98.4% on dutasteride 5 mg and 94.7% on 0.5 mg, versus 70.8% on finasteride 5 mg (P < 0.001), with less variability; testosterone rose but stayed in the normal range. Men had prostate enlargement, not hair loss.
Read the study ↗Related
- DutasterideA stronger cousin of finasteride that blocks both forms of the DHT-making enzyme and grew more hair than finasteride in head-to-head trials.
- MinoxidilThe most widely used hair-growth treatment, available as a cheap over-the-counter lotion or foam and as a prescription tablet, with a mechanism that is still only partly understood.
- Saw palmettoA berry extract with weak DHT-blocking activity that shows small benefits in short, mostly industry-linked trials and clearly less than finasteride in the one head-to-head.
- ClascoteroneA topical androgen blocker already approved as an acne cream whose 5% scalp solution reported positive phase 3 results in men; it is not yet approved for hair.
- Post-finasteride syndromeSome men report sexual, mental and physical symptoms that start on finasteride and last after stopping; whether it is a distinct drug-caused condition is still unresolved.
- DHT and pattern hair lossPattern hair loss happens when genetically sensitive scalp follicles respond to the hormone DHT by shrinking a little more with every hair cycle.
- Antiandrogen comparison for hair lossA side-by-side of the drugs, topicals and supplements that work on the androgen pathway, with who they were studied in and how strong the evidence is.