Dutasteride is more effective than finasteride at stopping hair loss and regrowing hair, but it carries a higher risk of side effects and is not FDA approved for androgenetic alopecia. Dutasteride 0.5mg blocks over 90% of DHT by inhibiting both type I and type II 5-alpha reductase enzymes, compared to finasteride 1mg which blocks about 70% through type II alone.
This article is for informational purposes only and does not constitute medical advice. Consult a physician before starting or changing any medication.
Quick Comparison
| Factor | Dutasteride (0.5mg) | Finasteride (1mg) |
|---|---|---|
| Brand name | Avodart | Propecia |
| DHT reduction | 90%+ | ~70% |
| Enzyme target | Type I and Type II 5-alpha reductase | Type II only |
| FDA approved for hair loss | No (off-label) | Yes |
| FDA approved for BPH | Yes | Yes |
| Half-life | 4 to 5 weeks | 6 to 8 hours |
| Time to results | 3 to 6 months | 3 to 6 months |
| Hair count increase (24 weeks) | ~109 hairs/cm2 | ~75 hairs/cm2 |
| Cost per month (generic) | $15 to $45 | $10 to $30 |
| Sexual side effects rate | 6 to 8% | 3 to 5% |
How DHT Blockers Work
Dihydrotestosterone (DHT) is the primary hormone responsible for androgenetic alopecia. In men with a genetic predisposition, DHT binds to receptors in hair follicles and triggers a process called follicular miniaturization. Over time, affected follicles produce thinner, shorter hairs until they stop producing visible hair entirely.
Both dutasteride and finasteride reduce DHT levels by blocking 5-alpha reductase, the enzyme that converts testosterone to DHT. The key difference is which types of the enzyme each drug targets.
The Two Types of 5-Alpha Reductase
| Enzyme Type | Location | Blocked By |
|---|---|---|
| Type I | Skin, sebaceous glands, liver | Dutasteride only |
| Type II | Hair follicles, prostate, liver | Both dutasteride and finasteride |
Finasteride inhibits only type II, which is the primary enzyme in hair follicles. This reduces scalp DHT levels by approximately 70%. Dutasteride inhibits both types, pushing total DHT suppression above 90%. The additional suppression from blocking type I in the skin and sebaceous glands is what gives dutasteride its edge in clinical efficacy.
Efficacy Data
Clinical Trial Results
The most cited head-to-head comparison is a 2004 randomized controlled trial published in the Journal of the American Academy of Dermatology that compared dutasteride at multiple doses against finasteride 5mg and placebo over 24 weeks.
| Treatment Group | Hair Count Change (hairs/cm2) | Improvement vs Placebo |
|---|---|---|
| Dutasteride 0.5mg | +109.6 | Significant |
| Dutasteride 0.1mg | +78.5 | Significant |
| Dutasteride 0.05mg | +56.5 | Significant |
| Finasteride 5mg | +75.6 | Significant |
| Placebo | -32.3 | Baseline |
Dutasteride 0.5mg outperformed finasteride 5mg (a dose five times higher than the standard 1mg hair loss dose), producing roughly 45% more hair regrowth. The difference was statistically significant.
Long-Term Maintenance
A separate Korean study followed patients on dutasteride 0.5mg for up to 48 months. Results showed continued improvement through month 24 with stabilization afterward. Finasteride studies show a similar pattern, with peak results at 12 to 24 months and maintenance thereafter.
Both drugs lose effectiveness if you stop taking them. Hair loss typically resumes within 6 to 12 months of discontinuation. Dutasteride's longer half-life (4 to 5 weeks) means DHT levels rise more slowly after stopping compared to finasteride (6 to 8 hours), but the endpoint is the same.
Side Effects
Both medications share similar side effect profiles because they work through the same mechanism. Dutasteride produces side effects at a higher rate because of its more aggressive DHT suppression.
Side Effect Comparison
| Side Effect | Dutasteride | Finasteride |
|---|---|---|
| Decreased libido | 3 to 5% | 1.8 to 3% |
| Erectile dysfunction | 3 to 5% | 1.3 to 3% |
| Ejaculatory disorders | 1 to 3% | 1 to 2% |
| Breast tenderness/gynecomastia | 1 to 2% | 0.4 to 1% |
| Depression or mood changes | Reported, frequency unclear | Reported, frequency unclear |
Important Context on Side Effects
The majority of men taking either drug experience no sexual side effects. In clinical trials, the placebo group reported sexual side effects at rates of 1 to 2%, indicating that some reports are unrelated to the medication.
The concept of "post-finasteride syndrome" (persistent sexual side effects after discontinuation) remains controversial. Some patients report lasting effects, but large-scale epidemiological studies have not confirmed a causal relationship. This debate applies equally to dutasteride.
Because dutasteride has a half-life of 4 to 5 weeks, any side effects take significantly longer to resolve after stopping. With finasteride, most side effects clear within days to weeks. With dutasteride, resolution can take several months.
Dutasteride and PSA Testing
Both drugs reduce PSA (prostate-specific antigen) levels by approximately 50%. If you are taking either medication and need a PSA test for prostate cancer screening, inform your doctor so they can adjust the reading accordingly. A "normal" PSA on dutasteride or finasteride could actually be elevated when accounting for the drug's suppressive effect.
FDA Status and Prescribing
Finasteride 1mg is FDA approved for androgenetic alopecia and has been since 1997 (brand name Propecia). It is the standard first-line prescription treatment for male pattern hair loss worldwide.
Dutasteride 0.5mg is FDA approved only for benign prostatic hyperplasia (BPH), sold under the brand name Avodart. Its use for hair loss in the United States is off-label, meaning doctors can legally prescribe it but it was not specifically tested and approved by the FDA for this purpose.
In South Korea and Japan, dutasteride is approved for androgenetic alopecia, reflecting the stronger clinical evidence base that has accumulated since the original BPH approval.
How Doctors Typically Prescribe
Most dermatologists and hair loss specialists follow this sequence:
- Start with finasteride 1mg daily
- Evaluate results at 6 to 12 months
- If response is inadequate, switch to dutasteride 0.5mg daily
- Add topical minoxidil at any stage for combination therapy
Dutasteride is rarely prescribed as a first-line treatment due to its off-label status, longer half-life (making side effect management harder), and the fact that finasteride works adequately for the majority of patients.
Cost Comparison
Monthly Cost (Generic, US)
| Medication | Brand Name | Generic Price |
|---|---|---|
| Finasteride 1mg | Propecia | $10 to $30/month |
| Dutasteride 0.5mg | Avodart | $15 to $45/month |
Annual Cost Comparison
| Period | Finasteride | Dutasteride |
|---|---|---|
| Year 1 | $120 to $360 | $180 to $540 |
| 5 years | $600 to $1,800 | $900 to $2,700 |
| 10 years | $1,200 to $3,600 | $1,800 to $5,400 |
Insurance sometimes covers dutasteride under the BPH indication but rarely covers finasteride for hair loss specifically. Some patients find that a BPH diagnosis alongside their hair loss prescription helps with insurance reimbursement. Discuss this with your prescribing physician.
For a detailed breakdown of finasteride pricing by source, see our finasteride cost guide.
Which Drug Is Right for You
Choose Finasteride If
- You are starting DHT blocker therapy for the first time
- You want an FDA-approved option for hair loss
- You prefer a shorter half-life for easier discontinuation if needed
- Your hair loss is Norwood 2 to 4 (moderate)
- You want to minimize side effect risk
Choose Dutasteride If
- Finasteride alone has not produced adequate results after 12+ months
- You have aggressive or rapidly progressing hair loss
- Your dermatologist recommends it based on your specific pattern
- You understand the off-label status and longer half-life implications
- You are at Norwood 4 to 6 and need stronger DHT suppression
Combination Strategies
Many patients achieve the best results by combining a DHT blocker with other treatments. Common combinations include:
| Combination | Expected Benefit |
|---|---|
| Finasteride + minoxidil 5% | DHT reduction + improved blood flow and follicle stimulation |
| Dutasteride + minoxidil 5% | Maximum DHT reduction + improved blood flow |
| Finasteride + microneedling | DHT reduction + collagen remodeling and growth factor release |
| Dutasteride + topical finasteride | Oral systemic + localized scalp DHT reduction (used in some clinics) |
The Norwood scale determines how aggressive your treatment plan needs to be. Patients at lower stages often do well on finasteride alone. Higher Norwood stages typically require combination therapy or a switch to dutasteride. Use our Norwood scale guide to identify your current stage.
Next Step
Not sure which treatment fits your hair loss pattern? Upload a photo at myhairline.ai/analyze to get your Norwood stage assessment and a personalized treatment recommendation, including whether finasteride, dutasteride, or a combination protocol makes sense for your situation.