Finasteride vs Dutasteride
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Finasteride and dutasteride are both 5-alpha reductase inhibitors (5-ARIs) used primarily to treat benign prostatic hyperplasia (BPH) and, in the case of finasteride, androgenetic alopecia (male pattern hair loss) [1][2]. They work by blocking the enzyme 5-alpha reductase, which converts testosterone to dihydrotestosterone (DHT) — a hormone responsible for prostate growth and hair follicle miniaturization.
Finasteride (brand names Proscar for BPH, Propecia for hair loss) was the first 5-ARI approved by the FDA, receiving approval for BPH in 1992 and for male pattern hair loss in 1997 [1]. It selectively inhibits type II 5-alpha reductase. Dutasteride (brand name Avodart) was approved in 2001 for BPH and inhibits both type I and type II 5-alpha reductase isoenzymes, resulting in more complete DHT suppression [2].
The key pharmacological difference is the degree of DHT suppression: finasteride reduces serum DHT by approximately 70%, while dutasteride suppresses it by about 90-95% [1][2]. This difference, along with dutasteride's much longer half-life, leads to distinct clinical considerations that patients and providers should understand when choosing between these medications.
Finasteride vs Dutasteride: Side-by-side comparison
| Category | Finasteride | Dutasteride |
|---|---|---|
| Drug Class | 5-alpha reductase inhibitor (type II) | 5-alpha reductase inhibitor (type I and II) |
| Brand Names | Proscar (BPH), Propecia (hair loss) | Avodart (BPH) |
| FDA-Approved Uses | BPH, male pattern hair loss | BPH |
| Typical Dosage | 5 mg daily (BPH), 1 mg daily (hair loss) | 0.5 mg daily |
| DHT Suppression | ~70% | ~90-95% |
| Half-Life | 6-8 hours | ~5 weeks |
| Time to Effect | 3-6 months | 3-6 months |
| Common Side Effects | Decreased libido, ED, ejaculation changes | Decreased libido, ED, ejaculation changes, gynecomastia |
| Pregnancy Warning | Women must not handle crushed tablets | Women must not handle capsules; 6-mo blood donation wait |
| Generic Cost (30-day) | $5-$20 | $10-$25 |
Efficacy: How well does each drug work?
For benign prostatic hyperplasia, both finasteride and dutasteride have demonstrated significant efficacy in reducing prostate volume, improving urinary symptoms, and decreasing the risk of acute urinary retention and BPH-related surgery [1][2][3].
The landmark CombAT (Combination of Avodart and Tamsulosin) trial compared dutasteride, tamsulosin, and their combination in men with moderate-to-severe BPH symptoms [3]. At 4 years, dutasteride alone reduced prostate volume by 28% and decreased the relative risk of acute urinary retention by 57% compared to placebo. The PLESS (Proscar Long-term Efficacy and Safety Study) showed finasteride reduced prostate volume by approximately 25% and decreased the risk of surgery by 55% over 4 years [4].
Head-to-head comparisons are limited. The EPICS (Enlarged Prostate International Comparator Study) trial compared dutasteride and finasteride directly in men with BPH and found no statistically significant difference in IPSS (International Prostate Symptom Score) improvement at 12 months [5]. However, dutasteride achieved greater DHT suppression, and some analyses suggest it may provide modestly greater prostate volume reduction in very large prostates.
For male pattern hair loss, finasteride 1 mg (Propecia) is FDA-approved and supported by robust clinical trial data showing increased hair count and improved patient satisfaction over 1-2 years [1]. Dutasteride is used off-label for hair loss in some countries and may be slightly more effective due to greater DHT suppression, but it is not FDA-approved for this indication in the United States [2].
Side effects comparison
Finasteride and dutasteride share a similar side effect profile related to their antiandrogen mechanism [1][2].
The most commonly reported side effects for both include decreased libido (1.8-6.4%), erectile dysfunction (1.3-8.1%), ejaculation disorders including decreased volume (0.8-4.4%), and breast tenderness or enlargement (gynecomastia, 0.5-2.8%) [1][2]. In clinical trials, these sexual side effects occurred in a small minority of patients and were generally reversible upon discontinuation. However, there have been post-market reports of sexual side effects persisting after drug discontinuation, sometimes referred to as "post-finasteride syndrome," though this remains a topic of ongoing research and debate [6].
Dutasteride's more complete DHT suppression and significantly longer half-life (5 weeks vs. 6-8 hours for finasteride) means that if sexual side effects occur, they may take longer to resolve after stopping dutasteride compared to finasteride [2]. Both medications are absolutely contraindicated in women who are or may become pregnant, as they can cause birth defects in male fetuses [1][2]. Women of childbearing age should not handle crushed or broken tablets. Due to dutasteride's long half-life, blood donation should be avoided for 6 months after the last dose [2].
Both medications can decrease prostate-specific antigen (PSA) levels by approximately 50%, which must be accounted for when screening for prostate cancer [1][2]. PSA values should be doubled for comparison with normal reference ranges in men taking either drug.
Cost comparison
Both finasteride and dutasteride are available as affordable generics [7].
Generic finasteride 5 mg (for BPH) typically costs $5-$15 for a 30-day supply. Generic finasteride 1 mg (for hair loss) is similarly priced at $8-$20 per month. Generic dutasteride 0.5 mg generally costs $10-$25 for a 30-day supply [7]. Brand-name versions are substantially more expensive. Insurance coverage for BPH indications is generally good for both; coverage for hair loss treatment with finasteride 1 mg varies.
Convenience and dosing
Both medications are taken once daily as an oral capsule or tablet, making convenience comparable [1][2].
Finasteride is available as 1 mg tablets (Propecia, for hair loss) and 5 mg tablets (Proscar, for BPH). Dutasteride is available as 0.5 mg soft gelatin capsules, which should be swallowed whole and not crushed or chewed [2].
A notable practical difference is washout time. Finasteride's short half-life (6-8 hours) means its effects diminish relatively quickly after discontinuation. Dutasteride's extremely long half-life (approximately 5 weeks) means the drug remains in the body for months after the last dose [2].
Which is right for you?
The choice between finasteride and dutasteride depends on the specific indication, treatment goals, and individual risk tolerance [1][2].
For BPH, clinical trial evidence suggests both drugs are comparably effective for most patients [5]. Dutasteride may offer a modest advantage in men with very large prostates due to its more complete DHT suppression. Combination therapy with a 5-ARI plus an alpha-blocker (such as tamsulosin) is superior to either drug alone for moderate-to-severe BPH [3].
For male pattern hair loss, finasteride 1 mg is the standard choice as the only FDA-approved 5-ARI for this indication [1]. Dutasteride may be considered off-label for patients who do not respond adequately to finasteride, though patients should understand its longer side effect washout period and off-label status.
This information is for educational purposes only and does not constitute medical advice. Consult your healthcare provider or urologist to determine which medication is appropriate for your condition.
Frequently asked questions
Do Finasteride and Dutasteride interact?
ModerateReferences
- [Regulatory] Proscar (finasteride 5 mg) prescribing information. Merck. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/020788s029lbl.pdf Accessed 2026-02-28.
- [Regulatory] Avodart (dutasteride) prescribing information. GlaxoSmithKline. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/021319s035lbl.pdf Accessed 2026-02-28.
- [Regulatory] Roehrborn CG, et al. CombAT: dutasteride and tamsulosin combination therapy. Eur Urol. 2010;57(1):123-131. https://doi.org/10.1016/j.eururo.2009.11.041 Accessed 2026-02-28.
- [Regulatory] McConnell JD, et al. Long-term effect of finasteride on BPH (PLESS). N Engl J Med. 1998;338(9):557-563. https://doi.org/10.1056/NEJM199810223391701 Accessed 2026-02-28.
- [Regulatory] Nickel JC, et al. Dutasteride vs finasteride for BPH (EPICS). BJU Int. 2011;108(3):388-394. https://doi.org/10.1111/j.1464-410X.2011.10181.x Accessed 2026-02-28.
- [Regulatory] Irwig MS. Persistent sexual side effects of finasteride. J Sex Med. 2012;9(11):2927-2932. https://pubmed.ncbi.nlm.nih.gov/22789024/ Accessed 2026-02-28.
- [Observational] GoodRx. Current pricing for generic finasteride and dutasteride. https://www.goodrx.com/ Accessed 2026-02-28.
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