Oral Prescription · Hair Loss

Finasteride & Dutasteride

How this page was made

This page was written with AI assistance and reviewed against the sources listed under References below. It is general information only, not medical advice. See our full disclaimer for how SHEA creates and reviews treatment information.

What they are

Finasteride and dutasteride are medications that reduce the production of dihydrotestosterone (DHT). DHT plays an important role in androgenetic alopecia by contributing to the gradual miniaturization of genetically susceptible hair follicles.

Both medications inhibit an enzyme called 5-alpha reductase, which converts testosterone to DHT. Finasteride primarily inhibits type II 5-alpha reductase, while dutasteride inhibits both type I and type II. Dutasteride therefore generally suppresses circulating DHT more strongly than finasteride.

Finasteride

Dutasteride

Inhibits type II 5-alpha reductase

Inhibits type I and type II 5-alpha reductase

Produces weaker suppression of serum DHT than dutasteride

Produces stronger suppression of serum DHT due to its broader enzyme inhibition

1 mg daily has been FDA-approved in the United States for male pattern hair loss since 1997

Not FDA-approved for hair loss in the United States; 0.5 mg daily has been approved in South Korea for male androgenetic alopecia since 2009

Plasma half-life measured in hours

Much longer half-life, measured in weeks

The stronger DHT suppression produced by dutasteride does not automatically mean that it is the right choice for every patient. The two drugs have different regulatory histories, pharmacology and evidence bases, and treatment choice is a medical decision.

Why people consider them

To slow progression of male androgenetic alopecia
To help maintain existing hair over the longer term
To potentially improve hair density in follicles affected by androgenetic alopecia
To discuss dutasteride as an alternative where it is approved for male androgenetic alopecia, including South Korea

What the experience is like

For male androgenetic alopecia, finasteride is commonly taken as a 1 mg oral tablet once daily. Dutasteride is approved in South Korea for male androgenetic alopecia at 0.5 mg daily.

Changes in hair growth are gradual rather than immediate. Studies generally assess results over months, and continued treatment is needed to maintain the drug's effect on DHT. Hair loss can resume after treatment is stopped.

Both medications can lower blood levels of prostate-specific antigen (PSA). Someone taking a 5-alpha reductase inhibitor should tell the clinician interpreting a PSA test because the medication can affect the result.

Limitations & considerations

Pregnancy and breastfeeding are important safety issues

Finasteride and dutasteride can interfere with development of the external genitalia of a male fetus and should not be used during pregnancy. Product labeling also warns pregnant people against handling crushed or broken tablets because the drugs may be absorbed through the skin. These medications are not indicated for use in women, and there are insufficient data regarding exposure during breastfeeding. Use in women requires separate medical assessment rather than assuming that evidence and labeling for male androgenetic alopecia apply in the same way.

Sexual adverse effects reported with 5-alpha reductase inhibitors include decreased libido, erectile dysfunction and ejaculatory disorders. Estimates vary between studies and populations
Persistent sexual symptoms after discontinuing finasteride have been reported. Their frequency, mechanisms and relationship to treatment remain areas of continuing research
Dutasteride remains in the body substantially longer than finasteride because of its much longer half-life
Dutasteride suppresses DHT more strongly, but greater hormonal suppression should not by itself be interpreted as proof that it is the better choice for an individual patient
Evidence in women is considerably more limited than in men, and regulatory indications differ
Both drugs can affect PSA measurements, which matters when PSA is being used in prostate assessment
Benefits generally require continued treatment. Neither medication permanently removes the underlying tendency toward androgenetic alopecia
No specific amount of hair maintenance or regrowth can be guaranteed

Evidence note

Finasteride's use in male androgenetic alopecia dates to its 1997 FDA approval and has since been studied in numerous trials. Dutasteride inhibits both major forms of 5-alpha reductase and suppresses circulating DHT more strongly, which has led to direct comparisons between the two medications.

A 2024 systematic review included nine studies comparing finasteride and dutasteride for androgenetic alopecia: four randomized controlled trials, one single-arm trial, two prospective cohort studies and two retrospective cohort studies. Seven studies included men only and two included women. The review found greater increases in hair count with some dutasteride regimens than with finasteride 1 mg, while finding no significant difference in adverse events between the drugs. Evidence involving women was much more limited, so these findings should not be interpreted as equally supported by evidence for male and female androgenetic alopecia.

South Korea is important when interpreting dutasteride evidence because 0.5 mg daily has been approved there for male androgenetic alopecia since 2009. This differs from the United States, where dutasteride is approved for benign prostatic hyperplasia rather than hair loss.

A 2022 multicenter retrospective chart review included 600 South Korean men treated with dutasteride or finasteride. Among patients receiving recommended on-label dosing, dutasteride was associated with greater improvement in one component of the BASP hair-loss classification. This was an observational chart review rather than a randomized trial, and the treatment groups differed at baseline, including in age and hair-loss severity.

The 2022 Korean study has an important conflict-of-interest consideration. Four authors were employees of GSK, the manufacturer of Avodart (dutasteride), and three of those employees reported holding GSK stock. Several additional authors worked for Analysis Group, a consulting firm that received funding for the study. These relationships do not invalidate the results, but they are relevant when interpreting an observational study whose findings favored dutasteride.

Sexual adverse effects are a recognized consideration with 5-alpha reductase inhibitors, but estimates differ depending on the drug, indication and studies included. Persistent symptoms after stopping finasteride have also been reported, while their frequency and mechanisms remain uncertain. This is an area where the evidence does not support either dismissing persistent symptoms or presenting them as an expected outcome.

References

Peer-reviewed literature and regulatory prescribing information.

1. Almudimeegh A, AlMutairi H, AlTassan F, AlQuraishi Y, Nagshabandi KN. Comparison between dutasteride and finasteride in hair regrowth and reversal of miniaturization in male and female androgenetic alopecia: a systematic review. Dermatology Reports, 2024;16(4):9909.

Peer-reviewed · Systematic review · 9 studies

2. Choi GS, Sim WY, Kang H, et al. Long-Term Effectiveness and Safety of Dutasteride versus Finasteride in Patients with Male Androgenic Alopecia in South Korea: A Multicentre Chart Review Study. Annals of Dermatology, 2022;34(5):349–359.

Peer-reviewed · Retrospective multicenter chart review · n=600 men · Industry involvement disclosed

3. Finasteride (Propecia) prescribing information. Indication, dosing, pregnancy information, adverse reactions and effects on PSA.

Regulatory prescribing information · Finasteride

4. Dutasteride prescribing information and South Korean regulatory information for the treatment of male androgenetic alopecia at 0.5 mg daily.

Regulatory information · Dutasteride · South Korea

5. Lee S, Lee YB, Choe SJ, Lee WS. Adverse Sexual Effects of Treatment with Finasteride or Dutasteride for Male Androgenetic Alopecia: A Systematic Review and Meta-analysis. Acta Dermato-Venereologica, 2019;99(1):12–17.

Peer-reviewed · Systematic review and meta-analysis · 15 RCTs · n=4,495

6. Hirshburg JM, Kelsey PA, Therrien CA, Gavino AC, Reichenberg JS. Adverse Effects and Safety of 5-alpha Reductase Inhibitors (Finasteride, Dutasteride): A Systematic Review. The Journal of Clinical and Aesthetic Dermatology, 2016;9(7):56–62.

Peer-reviewed · Systematic review