We use essential cookies (authentication, your saved goals/stack) by default. With your permission we’ll also enable privacy-respecting analytics (Vercel Web Analytics, anonymous load-time metrics) and error-replay diagnostics (Sentry — DOM snapshots only when an error fires) so we can fix bugs faster. Learn more about cookies
Dutasteride (Avodart) — dual 5α-reductase (type I + II) inhibitor
A dual 5α-reductase (type I + II) inhibitor approved for benign prostatic hyperplasia and used off-label for male pattern hair loss. It suppresses DHT more deeply than finasteride (which blocks only type II), and at 2.5 mg (five times the approved dose) it beat finasteride for hair count in one 24-week trial. It carries the same sexual and mood side-effect concerns as finasteride — with a much longer half-life, so any persistent effects clear more slowly. A prescription drug, not a supplement, and not a longevity drug.
Prescription medication — not a dietary supplement
Dutasteride is a prescription (or investigational) drug, not a supplement. It is included here for reference because people research and discuss it (often used off-label) — not as a recommendation. Take it only under a qualified clinician's supervision and only as prescribed; do not source it from grey-market vendors, where identity, purity, and dosing are unverified. The evidence below reflects its clinical trials.
What the evidence says
Dutasteride doesn't have enough studies with structured effect-size data yet to pool a verdict. Browse the studies below for individual findings.
Most evidence is from high-quality meta-analyses and randomised trials published 2006–2026 with a typical study size of 6,729 participants.
Based on 63 studies · 14 meta-analyses · 38 RCTs · 295,308 total participants
Confidence
High confidenceBy outcome
Dutasteride has solid randomized evidence: head-to-head superiority over finasteride for hair count (Olsen 2006), a placebo-controlled phase-III hair RCT, the CombAT BPH outcomes trial, and the large REDUCE prostate-cancer-prevention RCT. A network meta-analysis supports efficacy for androgenetic alopecia, with no significant difference from finasteride. The score is held below the top tier by shared 5ARI sexual side effects, a dutasteride-specific depression signal in meta-analysis, the high-grade-cancer nuance in REDUCE, and its long half-life (slower washout of any persistent effects). It is effective for hair and BPH but is not a longevity drug.
12 trials ongoing or recruiting · 108 completed on ClinicalTrials.gov
39 of the completed trials have posted results
Registered trials show research momentum for Dutasteride, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Nov 2026
Dutasteride (Avodart) is a dual 5α-reductase inhibitor that blocks both the type-I and type-II isoenzymes that convert testosterone to dihydrotestosterone (DHT).
Finasteride blocks mainly type II; dutasteride blocks both, so it lowers serum and scalp DHT more completely (>90% serum DHT suppression vs ~70% for finasteride).
It is FDA-approved at 0.5 mg/day for benign prostatic hyperplasia (BPH), where the REDUCE trial found less acute urinary retention than placebo (1.6% vs 6.7%), and the CombAT trial (no placebo arm) found that adding the alpha-blocker tamsulosin improved symptoms and progression more than either drug alone, though not retention or surgery compared with dutasteride alone.
For hair, it is used off-label (approved for androgenetic alopecia in South Korea and Japan, not the US): the Olsen 2006 dose-ranging RCT showed dutasteride 2.5 mg beat finasteride 5 mg for hair count, the dutasteride 0.5 mg phase-III RCT beat placebo, and a network meta-analysis found dutasteride 0.5 mg and finasteride not significantly different from each other in efficacy.
In the REDUCE prostate-cancer-prevention trial it cut overall prostate-cancer detection by ~23%, but with a small excess of high-grade (Gleason 8–10) tumors in years 3–4 (12 vs 1), and the composite category of cardiac failure was more common on dutasteride (0.7% vs 0.4%), an imbalance CombAT also reported.
The honest trade-off: dutasteride is genuinely more potent than finasteride and effective for both BPH and hair, but it shares the class's sexual side effects (reduced libido, erectile dysfunction, ejaculatory problems, significant in pooled BPH trials but not in pooled hair-loss trials) and a signal for depression that meta-analysis tied specifically to dutasteride rather than finasteride.
Its terminal half-life is ~5 weeks (vs ~6–8 hours for finasteride), so it accumulates and washes out slowly — relevant to anyone worried about persistent, post-finasteride-syndrome-type effects. It is a prescription drug, not a supplement, and there is no evidence it extends lifespan.
Blocks both isoenzymes that convert testosterone to DHT — unlike finasteride, which blocks mainly type II — producing deeper (>90%) serum and scalp DHT suppression.
Lower scalp DHT slows follicle miniaturization (hair benefit); lower prostate DHT shrinks the gland (BPH benefit).
Dutasteride accumulates and clears slowly — far longer than finasteride's ~6–8 hours — so DHT suppression and any persistent effects wash out slowly.
How Dutasteride works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Contraindicated — do not handle leaking capsules; absorbed through skin and can harm a male fetus.
Defer blood donation for at least 6 months after the last dose (long half-life; protects a potential pregnant recipient).
Caution — discuss the class side-effect profile and dutasteride-specific depression signal before starting.
Tell your clinician — 5ARIs lower PSA ~50%; interpret screening accordingly.
Can raise dutasteride levels; the long half-life already favors accumulation.
Combined intentionally for BPH (CombAT); additive effect on urinary symptoms, monitor blood pressure. CombAT also reported an imbalance in cardiac failure across its arms (no placebo arm).
Tip: Often improves with continued use or after stopping; discuss with a clinician.
Tip: Shared 5ARI class effect; weigh against benefit. May persist in a minority; long half-life slows resolution.
Tip: Meta-analysis tied a depression signal specifically to dutasteride; monitor mood and stop if it emerges.
Tip: Report new breast lumps; rarely a sign of male breast cancer.
Tip: 5ARIs roughly halve PSA — double the reading for screening; REDUCE showed a small excess of Gleason 8–10 tumors.
Tip: Monotherapy: in the 4-year REDUCE trial the composite term of cardiac failure occurred in 0.7% (30 men) on dutasteride against 0.4% (16 men) on placebo (P=0.03). Combination: CombAT, which had no placebo arm, reported an imbalance in cardiac failure across the dutasteride, tamsulosin and combination arms. A measured signal, not an established cause. Tell the prescriber about any heart failure history or new breathlessness or swelling.
Dutasteride has an evidence score of 5.4/10 — moderate evidence based on 63 indexed studies, including 3 meta-analyses. A dual 5α-reductase (type I + II) inhibitor approved for benign prostatic hyperplasia and used off-label for male pattern hair loss. It suppresses DHT more deeply than finasteride (which blocks only type II), and at 2.5 mg (five times the approved dose) it beat finasteride for hair count in one 24-week trial. It carries the same sexual and mood side-effect concerns as finasteride — with a much longer half-life, so any persistent effects clear more slowly. A prescription drug, not a supplement, and not a longevity drug. Representative study: PMID 23768246.
Dosing for Dutasteride: Approved BPH dose is 0.5 mg once daily; off-label hair-loss use mirrors the same 0.5 mg once-daily dose under a clinician. A prescription drug. Individual needs vary, so check the right dose for you with a healthcare provider.
The best time to take Dutasteride is in the morning. It can be taken on an empty stomach. Once daily, with or without food.
Dutasteride should be used with caution — talk to a healthcare provider before taking it. Reported side effects include cardiac failure (trial signal), erectile / ejaculatory dysfunction, depressed mood. How often they occur is not established for all of them. Use caution if any of these apply to you: Women who are or may become pregnant (risk to a male fetus — DHT is required for male genital development); Children; Known hypersensitivity to dutasteride or other 5α-reductase inhibitors.
Finasteride
Too few graded studiesA prescription 5α-reductase type-II inhibitor that lowers DHT to treat male pattern hair loss (1 mg, Propecia) and benign prostatic hyperplasia (5 mg, Proscar). The hair and prostate benefits are well-proven in large RCTs. The honest caveats are real and prominent: sexual side effects (erectile dysfunction, decreased libido) in a minority of men, a disputed but important 'post-finasteride syndrome' with persistent symptoms, and a depression/suicidality safety signal in pharmacovigilance data. It is NOT a longevity drug.
Finasteride (topical)
Too few graded studiesThe same drug as oral finasteride, applied to the scalp — with a systemic-sparing claim that the pharmacokinetic data only partly supports.
Minoxidil (oral & topical)
Too few graded studiesA potassium-channel-opening vasodilator — originally an oral antihypertensive — whose well-documented hypertrichosis side effect made it the first FDA-approved hair-loss drug. Topical 2–5% (Rogaine) is OTC and proven in androgenetic alopecia; low-dose ORAL minoxidil (LDOM, ~0.25–5 mg) is an off-label, rapidly adopted alternative with real but generally mild cardiovascular/hypertrichosis side effects. A drug, not a supplement — and not a longevity compound.
Beta-Sitosterol
Too few graded studiesPlant sterol that improved BPH urinary symptoms and urine flow in placebo-controlled trials at 60 to 130 mg a day, without shrinking the prostate. Gram doses of plant sterols for cholesterol are a separate entry.
Explore: Best supplements for Skin, Hair & BeautyBest supplements for Men's Health
Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 63 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Tap node to isolate • Pinch to zoom • Tap edge for research