Both Propecia (finasteride) and Avodart (dutasteride) lower DHT, a hormone that shrinks hair follicles over time. Finasteride is FDA-approved for hair loss and blocks about 70% of scalp DHT. Dutasteride blocks closer to 90% and may regrow more hair, but it is off-label in the U.S.
| Drug | Scalp DHT Drop | FDA Approved? | Daily Dose | Cost | Best For |
|---|---|---|---|---|---|
| Finasteride | ~70% | Yes | 1 mg | $10–20/month | Early or mild loss, first-line treatment |
| Dutasteride | ~90% | No | 0.5 mg | $20–40/month | More aggressive loss or poor response to finasteride |
Propecia vs Avodart: Key Takeaways
- Finasteride (Propecia) and dutasteride (Avodart) both block DHT, the hormone responsible for miniaturizing hair follicles.
- Finasteride reduces scalp DHT by ~70% and is FDA-approved for hair loss; dutasteride reduces it by ~90% and is more potent but off-label in the U.S.
- Both medications are generally well-tolerated, but some users experience sexual or mood side effects.
- Treatment choice depends on age, family history, response to other therapies, and tolerance of risk.
If you’re comparing options after hearing about DHT blockers online, or you’ve already tried minoxidil, this article breaks down the real differences between Propecia and Avodart based on the latest research and expert consensus.
How These Drugs Work in Hair Follicles
Androgenetic alopecia is driven by DHT (dihydrotestosterone), a hormone made when testosterone is converted by an enzyme called 5-alpha reductase. DHT miniaturizes hair follicles, causing them to shrink and produce thinner, shorter hairs until they eventually stop growing.
Finasteride and dutasteride are 5-alpha reductase inhibitors that reduce this DHT-driven miniaturization.
But which drug is more effective?
Finasteride ≈ 70% scalp DHT drop
Finasteride blocks type II 5-alpha reductase, the version mainly found in hair follicles. Taking 1 mg daily reduces scalp DHT by about 60–70%. That’s enough to slow or halt loss in most men with early to moderate thinning.
Dutasteride ≈ 90% scalp DHT drop
Dutasteride blocks both type I and type II enzymes. Type I is found in the skin and sebaceous glands, while type II targets the follicle. That dual action drops DHT levels by 90% or more.
Efficacy for Hair Regrowth
Recent clinical data suggest that while both finasteride and dutasteride promote hair regrowth, dutasteride may offer superior results.
- In a 2014 randomized trial involving 917 men, dutasteride 0.5 mg led to a greater increase in hair count and shaft thickness within a 2.54 cm target area compared to both finasteride and placebo. Frontal scalp photographs taken over a 24-week period also showed more noticeable improvement with dutasteride. These effects were dose-dependent, reinforcing the drug’s potency as a dual 5-alpha reductase inhibitor.
- More recently, a 2025 network meta-analysis (Gupta et al., JAMA Dermatol) comparing various hair loss treatments ranked oral dutasteride 0.5 mg as the most effective medical therapy for male pattern hair loss (dutasteride 0.5 mg/day, taken orally, was more effective than either oral finasteride 1 mg/day or oral minoxidil 5 mg/day). Dutasteride outperformed finasteride and all minoxidil formulations in terms of increasing total and terminal hair density at 24 and 48 weeks.
On average, men taking dutasteride saw better density gains in less time, especially in the crown area. That said, finasteride still works well for most men, particularly if you start early.
Side-Effect Snapshot
Erectile dysfunction is the most frequently reported issue, followed by decreased ejaculatory volume and reduced libido. These effects appear in a small percentage of users and are typically dose-dependent and reversible upon discontinuation.
Sexual Dysfunction
Sexual adverse effects are the most frequently reported complications associated with finasteride use. Erectile dysfunction is the most common, followed by ejaculatory dysfunction and loss of libido.
In studies where patients were prescribed finasteride at 5 mg per day, findings indicate:
- Erectile dysfunction was reported in 3.4% to 15.8% of patients, compared to 1.7% to 6.3% in those on placebo.
- Decreased libido affected 2.36% to 10.0% of patients, versus 1.2% to 6.3% in the placebo group.
- Ejaculatory dysfunction occurred in 0.9% to 5.7% of patients, while 0.5% to 1.7% of placebo patients experienced it.
These side effects are usually mild and reversible when the medication is stopped.
Finasteride 5 mg daily is primarily indicated for benign prostatic hyperplasia (BPH) and is not commonly used in dermatologic settings. It’s also important to consider that prostate conditions themselves are independent risk factors for erectile dysfunction, which may confound assessments of sexual side effects in patients taking the higher dose.
Like finasteride users, some men taking dutasteride have reported sexual dysfunction. One study of dutasteride use in men with BPH found that:
- Erectile dysfunction occurred in 7.3%,
- Decreased libido in 4.2%,
- And ejaculation disturbances in 2.2% of patients.
Crucially, head-to-head trials for hair loss have found no statistically significant difference in sexual side effect rates between finasteride and dutasteride.8
Mood and Depression
There have been reports (mostly post-marketing) of mood changes, depression, and anxiety in some men taking 5-AR inhibitors. A 2020 pharmacovigilance analysis and a 2025 review highlighted a signal for increased reports of depression and suicidal ideation in finasteride users, particularly younger men.
While causation isn’t proven, the FDA added warnings about potential mood side effects. Dutasteride, by analogy, could have similar effects, though data are more limited. Overall, the risk appears low, but patients and doctors are advised to monitor for mood symptoms.
Pregnancy & Fetal Development
Women must not use or come into contact with these drugs if pregnant. Finasteride and dutasteride can cause birth defects in a male fetus by disrupting DHT (which is crucial for male genital development).
Dutasteride carries a greater risk because its half-life is 5-6 weeks, significantly longer than finasteride’s 4-6 hours.
Strategies to Mitigate Risk
- Quarter-dosing: Some men cut pills into quarters to find the lowest effective dose.
- Alternate-day use: Especially with dutasteride, which stays in your system longer.
- Cycle on/off: The concept of periodic breaks (e.g., 1–2 weeks off every few months) is discussed anecdotally to possibly reset any side effects.
- Topical versions: Especially finasteride. Lower systemic absorption, similar local DHT reduction.
FDA vs Off-Label Status
Finasteride (Propecia) is FDA-approved for male pattern hair loss at 1 mg/day. It’s the gold standard first-line prescription for AGA.
Dutasteride (Avodart) is not FDA-approved for hair loss. The medication is FDA-approved for the treatment of BPH, but its use for hair loss is considered off-label.
What that means in practice: Physicians can legally prescribe dutasteride for androgenetic alopecia if they determine it’s medically appropriate. However, insurance may not cover the cost, and you’ll need to provide informed consent acknowledging the off-label use.
International note: Dutasteride is officially approved for hair loss in Japan, South Korea, and Taiwan. In Asia, it’s often the first-line choice.
Choosing the Right Option
Age and Family History
If you’re in your 20s or early 30s with gradual thinning, finasteride is usually enough. Especially if you have a moderate family history or your hairline is just starting to recede.
If you’re noticing fast progression or have a family history of early baldness, dutasteride might be the stronger preventive play.
Combo Therapy with Minoxidil / LLLT / PRP
Stacking treatments improves your odds. Here are common combos:
- Minoxidil: Speeds up hair growth cycles. Comes in topical or oral form.
- LLLT (low-level laser therapy): At-home laser caps that stimulate blood flow to follicles.
- PRP (platelet-rich plasma): In-office injections of growth factors taken from your own blood.
These approaches are most effective when combined with a DHT-blocking medication. For a deeper look at complementary therapies, see our guide to non-surgical hair restoration options.
Cost & Convenience
Finasteride (1 mg daily): $10–20/month (generic)
Dutasteride (0.5 mg daily): $20–40/month (generic)
Topicals: Can run $60–90/month if compounded, especially for finasteride + minoxidil mixes.
Refill Cadence
- Finasteride: Daily pill, clears fast (half-life ~6 hours)
- Dutasteride: Can be taken less frequently in some cases (half-life ~5 weeks)
That long half-life makes dutasteride forgiving if you miss a dose—and some doctors prescribe it 2–3x/week instead of daily.
The Original Phase II Trial: Where It All Started
Before dutasteride became a mainstream off-label option, GlaxoSmithKline conducted a pivotal Phase II study that shaped everything we know about this medication’s potential for hair loss.
The trial enrolled 416 men with androgenetic alopecia (Norwood types IIIv, IV, or V) and compared multiple dutasteride doses against finasteride 5mg and placebo over 24 weeks, with a 12-week follow-up after stopping treatment.
What They Found: Hair Counts by Week
The results showed a clear dose-response relationship. Higher dutasteride doses produced more hair regrowth, and importantly, the effects lasted longer after stopping treatment.
| Treatment | Week 12 (hairs gained) | Week 24 (hairs gained) | Week 36 / 12 weeks after stopping (hairs maintained) |
|---|---|---|---|
| Dutasteride 0.05mg | +5 | +25 | -17 (lost gains) |
| Dutasteride 0.1mg | +54 | +72 | +17 (partial maintenance) |
| Dutasteride 0.5mg | +72 | +96 | +84 (strong maintenance) |
| Dutasteride 2.5mg | +100 | +110 | +120 (continued improvement) |
| Finasteride 5mg | +52 | +73 | +13 (lost most gains |
| Placebo | -23 | -30 | -37 (continued loss) |
* Hair counts measured in a 1-inch diameter circle (0.79 square inches) at the vertex.
The Key Discovery
The most striking finding wasn’t just that dutasteride grew more hair. It was what happened after men stopped taking the medication.
At week 36, twelve weeks after discontinuing treatment, men on dutasteride 0.5mg and 2.5mg maintained nearly all their gains. Men on finasteride 5mg lost most of theirs, dropping from +73 hairs to just +13.
This durability effect is likely due to dutasteride’s exceptionally long half-life (5-6 weeks vs finasteride’s 6 hours). The medication stays in your system much longer, providing a “buffer” period after discontinuation.
Side Effects in the Original Trial
The trial also tracked adverse events across all groups:
| Side Effect | Dutasteride 0.5mg | Dutasteride 2.5mg | Finasteride 5mg | Placebo |
|---|---|---|---|---|
| Any adverse event | 16% | +32% | 24% | 27% |
| Decreased libido | 0% | 13% | 4% | 3% |
| Headaches | 6% | 6% | 3% | 3% |
| Impotence | 0% | +0% | 1% | 5% |
At the 0.5mg dose (now the standard), sexual side effects were actually lower than placebo. The 2.5mg dose showed higher rates of decreased libido (13%), which is one reason the lower dose became standard practice.
Why This Still Matters
This Phase II data from over two decades ago established the scientific foundation for dutasteride’s off-label use in hair restoration. The 0.5mg dose emerged as the sweet spot: strong enough to produce meaningful results, low enough to minimize side effects.
Modern research has confirmed these early findings. The 2025 Gupta meta-analysis referenced earlier in this article builds on this foundation, showing dutasteride remains the most effective oral medication for androgenetic alopecia.
FAQs Men Ask in 2025
Does dutasteride ruin future transplants?
Not at all. In fact, it can preserve existing hair around transplanted areas, improving long-term results.
Can I switch from dutasteride back to finasteride?
Yes, though you may notice some regression if finasteride isn’t sufficient to maintain the gains achieved with dutasteride. Gradual tapering can help ease the transition and allow your provider to monitor any changes in shedding or density.
Will I lose hair if I stop taking it?
Yes. DHT levels return to normal, and miniaturization resumes. You’ll likely catch up to where you’d be without treatment.
Can I combine it with oral minoxidil?
Yes. This is a popular combo. Oral minoxidil stimulates regrowth while DHT blockers protect existing follicles.
Why isn’t dutasteride FDA-approved for hair loss if it works better?
GlaxoSmithKline conducted Phase II trials in the early 2000s but never completed the FDA approval process for hair loss. The exact reasons aren’t public, but likely factors include: the existing finasteride market, cost of Phase III trials, and the long half-life creating complex pregnancy warnings. Meanwhile, countries like Japan, South Korea, and Taiwan have approved it for hair loss.
Can I take dutasteride every other day instead of daily?
Yes, and some doctors prescribe it this way. Because dutasteride has a 5-6 week half-life (compared to finasteride’s 6 hours), it stays in your system much longer. Some men take it 2-3 times per week with good results. This approach may also reduce side effects. Discuss dosing frequency with your prescribing physician.
What happens if I switch from finasteride to dutasteride?
Most men who switch see additional improvement, particularly if finasteride wasn’t providing sufficient results. The transition is straightforward since both medications work through the same mechanism. You may notice increased shedding during the first few weeks as your body adjusts to the stronger DHT suppression, but this typically stabilizes.
Dutasteride vs Finasteride for Hair Loss – Conclusion
If you’re serious about keeping your hair, the best next step is a conversation with a hair restoration provider. At ForHair, we specialize in personalized treatment plans, including finasteride and dutasteride, as well as advanced therapies like stem cell, exosomes, and CRP therapy.
No one-size-fits-all. But the earlier you act, the more hair you keep
Let’s plan it right—Book your free consultation online to find out which option is right for your hair type, goals, and medical profile with our experts.
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