Dutasteride and finasteride are both 5-alpha reductase inhibitors used for BPH and hair loss, but they differ in potency, mechanism, and pharmacokinetics. Dutasteride blocks both Type 1 and Type 2 5-alpha reductase: the FDA label reports a median serum DHT decrease of 94% at 1 year on 0.5 mg/day. Finasteride blocks only Type 2: the Propecia label reports 65% suppression within 24 hours of a 1 mg tablet, the dose used for hair loss, and the Proscar label reports approximately 70% on 5 mg/day, the dose used for BPH. Head-to-head trials in androgenetic alopecia have generally favored dutasteride, though a 2014 network meta-analysis found no statistically significant efficacy difference between the active treatments. Finasteride is FDA-approved for hair loss; dutasteride is not, so all dutasteride use for hair loss is off-label.
Head-to-Head Comparison
| Feature | Dutasteride (Avodart) | Finasteride (Propecia/Proscar) |
|---|---|---|
| 5AR isoforms blocked | Type 1 + Type 2 | Type 2 only |
| Serum DHT reduction | ~94% at 1 year on 0.5 mg/day (FDA label) | ~70% on 5 mg/day (Proscar label); 65% within 24 hours of a 1 mg dose (Propecia label) |
| FDA-approved: BPH | Yes (0.5 mg) | Yes (5 mg / Proscar) |
| FDA-approved: hair loss | No (off-label) | Yes (1 mg / Propecia) |
| Terminal half-life | ~5 weeks (FDA label) | ~5-6 hours at 1 mg (Propecia label); ~6 hours at 5 mg, ~8 hours in men over 70 (Proscar label) |
| Time to steady state | ~6 months | ~1-2 weeks |
| Head-to-head hair count (24 wk) | Dutasteride 0.5 mg significantly greater than finasteride 1 mg in a 917-man randomized trial (p = 0.003) | |
| Generic available | Yes | Yes |
Efficacy: Which Works Better for Hair Loss?
Multiple randomized controlled trials have compared dutasteride and finasteride head-to-head for hair loss:
The Olsen et al. (2006) trial randomized 416 men aged 21 to 45 to dutasteride 0.05, 0.1, 0.5 or 2.5 mg, finasteride 5 mg, or placebo daily for 24 weeks. Dutasteride increased target area hair count over placebo in a dose-dependent fashion, and dutasteride 2.5 mg was superior to finasteride 5 mg at 12 and 24 weeks. The larger Gubelin Harcha et al. (2014) trial randomized 917 men to dutasteride 0.02, 0.1 or 0.5 mg, finasteride 1 mg, or placebo for 24 weeks. In that trial dutasteride 0.5 mg significantly increased both hair count and hair width in a 2.54 cm diameter target area compared with finasteride 1 mg (p = 0.003 and p = 0.004) and with placebo.
The IJDVL randomized study (Shanshanwal and Dhurat, 2017) compared dutasteride 0.5 mg daily with finasteride 1 mg daily, the dose actually prescribed for hair loss, in 90 men over 24 weeks. Total hair count rose more in the dutasteride group and thin-hair count fell more, which the authors read as greater reversal of miniaturization. Side-effect profiles were comparable. Read the study analysis.
Side Effects Comparison
Both drugs share similar side effect profiles (decreased libido, ED, ejaculation changes, gynecomastia), but dutasteride may have slightly higher rates due to more complete DHT suppression. The key difference is recovery time: finasteride clears the body within days (terminal half-life about 5 to 6 hours at the 1 mg dose), while dutasteride takes months (terminal half-life about 5 weeks).
Which Should You Choose?
Consider finasteride first if: You want an FDA-approved option for hair loss, prefer a shorter-acting drug with faster recovery if you stop, or want the lowest cost option.
Consider dutasteride if: Finasteride has not produced adequate results, you want maximum DHT suppression, or you are also treating BPH. Many patients switch to dutasteride after an insufficient response to finasteride.
Full Feature Comparison
| Feature | Dutasteride | Finasteride |
|---|---|---|
| Brand name | Avodart | Proscar (5 mg) / Propecia (1 mg) |
| Drug class | Dual 5-alpha reductase inhibitor | Selective 5-alpha reductase inhibitor |
| 5AR isoforms blocked | Type 1 and Type 2 | Type 2 only |
| Serum DHT reduction | ~94% at 1 year on 0.5 mg/day (FDA label) | ~65% at 1 mg, the hair-loss dose (Propecia label); ~70% at 5 mg (Proscar label) |
| Bioavailability | ~60% | ~65% |
| Terminal half-life | ~5 weeks (FDA label) | ~5-6 hours at 1 mg (Propecia label); ~6 hours at 5 mg, ~8 hours in men over 70 (Proscar label) |
| Time to steady state | 65% of steady state at 1 month, ~90% at 3 months (FDA label) | Days, given the short half-life |
| After stopping | Serum dutasteride stays detectable for 4 to 6 months (FDA label) | DHT returned to pretreatment levels in about 2 weeks in volunteers treated for 14 days (Proscar label) |
| FDA-approved: BPH | Yes, 0.5 mg (approved November 2001) | Yes, 5 mg as Proscar (approved June 1992) |
| FDA-approved: hair loss | No, so all hair-loss use is off-label | Yes, 1 mg as Propecia (approved December 1997) |
| Available strengths | 0.5 mg soft capsule only | 1 mg (Propecia), 5 mg (Proscar) |
| Combination BPH drug | Jalyn in the US (+ tamsulosin 0.4 mg); Duodart or Combodart elsewhere | None (no FDA-approved fixed-dose combination) |
| PSA reduction | ~50% within 3 to 6 months (FDA label) | ~50% within 6 months (Proscar label) |
| Blood donation deferral | 6 months after last dose (FDA label section 5.5) | Not specified in the Propecia or Proscar labeling |
| Use in pregnancy | Contraindicated (FDA label section 4) | Contraindicated (FDA label section 4) |
| Generic available | Yes (dutasteride) | Yes (finasteride) |
| Male breast cancer | Listed under postmarketing experience in the FDA label | Listed under postmarketing experience in the FDA label |
| High-grade prostate cancer signal | Yes (REDUCE trial; FDA label Warnings and Precautions 5.2, not a boxed warning) | Yes (Proscar label Warnings and Precautions 5.2, not a boxed warning) |
Head-to-Head Clinical Trial Results
These are the main published trials comparing dutasteride with finasteride for androgenetic alopecia, plus one open-label study in men who had already failed finasteride and one network meta-analysis:
| Study | n | Duration | Dutasteride result | Finasteride comparator | Winner |
|---|---|---|---|---|---|
| Olsen et al. (2006), J Am Acad Dermatol 55(6):1014-23 | 416 | 24 weeks | Dose-dependent increase in target area hair count vs placebo; 2.5 mg superior to finasteride at 12 and 24 weeks | Finasteride 5 mg daily | Dutasteride at 2.5 mg |
| Gubelin Harcha et al. (2014), J Am Acad Dermatol 70(3):489-498.e3 | 917 | 24 weeks | 0.5 mg significantly increased hair count and width in a 2.54 cm diameter target area (p = 0.003, p = 0.004) | Finasteride 1 mg daily | Dutasteride |
| Shanshanwal & Dhurat (2017), Indian J Dermatol Venereol Leprol 83(1):47-54 | 90 | 24 weeks | Significantly greater increase in total hair count and greater reversal of miniaturization | Finasteride 1 mg daily | Dutasteride |
| Jung et al. (2014), Int J Dermatol 53(11):1351-7 | 35 | 6 months | Open-label study in men who had not responded to finasteride 1 mg: 24 of 31 completers improved on global photography; hair density up 10.3% | No concurrent finasteride arm | Not a head-to-head comparison |
| Gupta & Charrette (2014), J Dermatolog Treat 25(2):156-61 | Network meta-analysis | Various | Active treatments were not significantly different from each other in efficacy | Finasteride 1 mg and 5 mg | No significant difference |
Treatment Timeline Comparison
| Timepoint | Dutasteride | Finasteride |
|---|---|---|
| First 1–2 months | Initial shedding may occur; no visible improvement | Initial shedding may occur; no visible improvement |
| 2–3 months | Serum DHT already deeply suppressed; the FDA label reports 85% at 1 week and 90% at 2 weeks of dosing | DHT suppressed; shedding slowing |
| 4–6 months | Miniaturized hairs beginning to thicken | First visible maintenance and early regrowth |
| 6–12 months | Visible improvement in density and caliber | Good maintenance; moderate regrowth for responders |
| 12–24 months | Maximum results | Results plateau; some late-phase regrowth |
| After stopping | Serum dutasteride stays detectable for 4 to 6 months (FDA label), so the effect fades slowly | The Propecia label states that withdrawal of treatment leads to reversal of effect within 12 months |
⚠️ Risk to a male fetus, both drugs: the FDA labels for dutasteride and finasteride both contraindicate use in pregnancy and in women who are or may become pregnant, because inhibiting the conversion of testosterone to DHT can cause abnormalities of the external genitalia of a male fetus. The letter-based pregnancy categories were removed from US labeling by the 2015 Pregnancy and Lactation Labeling Rule, so neither current label carries a “Category X” designation; the contraindication itself is unchanged. Women who are pregnant or may become pregnant must not handle crushed or broken tablets or leaking capsules. Because of dutasteride’s much longer half-life (~5 weeks vs about 5 to 6 hours for finasteride 1 mg), its label defers blood donation until at least 6 months after the last dose.
Dutasteride for hair loss · Side effects · Dosage · Dutasteride vs Finasteride for BPH
Dutasteride cuts serum DHT by about 94% at 0.5 mg/day; finasteride 1 mg reaches about 65% suppression. If you’re not getting the results you want from finasteride, a telehealth provider can evaluate whether dutasteride is right for you.
Dutasteride is not FDA-approved for hair loss. All use is off-label. Individual results vary. Consult a licensed healthcare provider.
Sources
- Olsen EA, et al. The importance of dual 5alpha-reductase inhibition in the treatment of male pattern hair loss: results of a randomized placebo-controlled study of dutasteride versus finasteride. J Am Acad Dermatol. 2006;55(6):1014-23. PubMed
- Gubelin Harcha W, et al. A randomized, active- and placebo-controlled study of the efficacy and safety of different doses of dutasteride versus placebo and finasteride in the treatment of male subjects with androgenetic alopecia. J Am Acad Dermatol. 2014;70(3):489-498.e3. PubMed
- Shanshanwal SJ, Dhurat RS. Superiority of dutasteride over finasteride in hair regrowth and reversal of miniaturization in men with androgenetic alopecia: a randomized controlled open-label, evaluator-blinded study. Indian J Dermatol Venereol Leprol. 2017;83(1):47-54. PubMed
- Jung JY, et al. Effect of dutasteride 0.5 mg/d in men with androgenetic alopecia recalcitrant to finasteride. Int J Dermatol. 2014;53(11):1351-7. PubMed
- Gupta AK, Charrette A. The efficacy and safety of 5α-reductase inhibitors in androgenetic alopecia: a network meta-analysis and benefit-risk assessment of finasteride and dutasteride. J Dermatolog Treat. 2014;25(2):156-61. PubMed
- Clark RV, et al. Marked suppression of dihydrotestosterone in men with benign prostatic hyperplasia by dutasteride, a dual 5alpha-reductase inhibitor. J Clin Endocrinol Metab. 2004;89(5):2179-84. PubMed
- FDA. Avodart (dutasteride) prescribing information. accessdata.fda.gov
- FDA. Proscar (finasteride) prescribing information. DailyMed
- FDA. Propecia (finasteride) prescribing information. DailyMed