Quick Answer: Finasteride 1 mg (Propecia) is FDA-approved to treat male pattern hair loss in men. Dutasteride 0.5 mg (Avodart) is FDA-approved only for symptomatic benign prostatic hyperplasia (BPH), so using it for hair loss in the US is off-label. Finasteride blocks the type 2 form of 5-alpha-reductase; dutasteride blocks types 1 and 2. In a 917-man randomized trial (Gubelin Harcha 2014), dutasteride 0.5 mg increased hair count more than finasteride 1 mg at 24 weeks, with similar adverse event rates, and a 2019 meta-analysis reached a similar conclusion. Dutasteride stays in the body much longer (terminal half-life about 5 weeks). Both lower PSA, both are hazardous to a male fetus, and both require a prescription and a conversation with a clinician.
Finasteride vs Dutasteride at a Glance
| Feature | Finasteride (Propecia) | Dutasteride (Avodart) |
|---|---|---|
| FDA-approved uses | Male pattern hair loss (1 mg); BPH (5 mg, Proscar) | Symptomatic BPH (0.5 mg); not approved for hair loss |
| Enzyme blocked | 5-alpha-reductase type 2 | 5-alpha-reductase types 1 and 2 |
| Usual dose (label) | 1 mg once daily for hair loss | 0.5 mg once daily (BPH label) |
| Time to see benefit (label) | Usually 3 months or more of daily use | Hair-loss use is off-label; trials ran 24 weeks |
| Elimination | Short half-life (hours) | Terminal half-life about 5 weeks; detectable 4–6 months after stopping |
| PSA effect | Lowers PSA; clinicians adjust interpretation | Lowers PSA by about 50% within 3–6 months |
| Blood donation | Ask the blood bank | Label: do not donate until 6 months after last dose |
| Pregnancy | Contraindicated; women should not handle crushed or broken tablets | Contraindicated; women should not handle leaking capsules |
Doses above are from the current U.S. Drug Facts or prescribing labels listed in Sources. Always follow the label on the package you buy, because store brands and formulations differ.
How Each Drug Works
Male pattern hair loss (androgenetic alopecia) is driven by genetics and by dihydrotestosterone (DHT), a hormone made from testosterone by an enzyme called 5-alpha-reductase. In genetically susceptible scalp follicles, DHT gradually shrinks (miniaturizes) hairs until they become fine and short. Lowering DHT slows that process and, in some men, lets miniaturized follicles produce thicker hair again.
There are two main forms of the enzyme. Finasteride selectively blocks the type 2 isoform. Dutasteride blocks both type 1 and type 2; the Avodart prescribing information describes it as a selective inhibitor of both isoforms. Because it blocks both, dutasteride suppresses DHT more completely, which is the main reason researchers have tested it for hair loss.
Regulatory Status: Approved vs Off-Label
The Propecia label states that finasteride 1 mg is indicated for the treatment of male pattern hair loss in men only, and that efficacy in bitemporal recession (receding at the temples) has not been established. The higher 5 mg strength (Proscar) is used for BPH.
The Avodart label lists only BPH: improving urinary symptoms, reducing the risk of acute urinary retention and reducing the risk of BPH-related surgery, alone or with tamsulosin. It is not FDA-approved for hair loss. Clinicians can prescribe a drug off-label when they judge it appropriate, but off-label use means the FDA has not reviewed the evidence for that purpose. Dutasteride for hair loss has been approved in some other countries (for example, South Korea), which is one reason most hair-loss trials of the drug come from Asia.
Head-to-Head Evidence
The largest randomized trial
Gubelin Harcha and colleagues (Journal of the American Academy of Dermatology, 2014) randomized 917 men aged 20 to 50 with male pattern hair loss to placebo, several doses of dutasteride, or finasteride 1 mg for 24 weeks. Hair count and width increased with dutasteride in a dose-dependent way. Dutasteride 0.5 mg significantly increased hair count and hair width in a defined scalp area, and improved panel ratings of frontal photographs, compared with both finasteride and placebo. The authors reported that the number and severity of adverse events were similar among groups, and noted the main limitation that the study lasted only 24 weeks.
Meta-analysis
A 2019 meta-analysis by Zhou and colleagues (Clinical Interventions in Aging) pooled three trials with 576 men comparing the two drugs. Dutasteride produced a larger mean increase in total hair count and better photographic and self-assessment scores. Rates of altered libido, erectile dysfunction and ejaculation disorders did not differ significantly between the drugs, though the number of trials was small.
What the evidence does not show
- Long-term data: most comparisons run 6 to 12 months. Finasteride has far longer follow-up in hair loss.
- Women: neither drug is FDA-approved for hair loss in women, and both are contraindicated in pregnancy.
- Individual response: average differences in hair count do not predict how any one person will respond.
Dosing and Timeline
Per the Propecia label, the dose is one 1 mg tablet daily, with or without food. Daily use for three months or more is generally needed before benefit is seen, continued use is needed to keep the benefit, and stopping treatment leads to reversal of the effect within 12 months.
Per the Avodart label, the BPH dose is one 0.5 mg capsule daily, swallowed whole; capsules should not be chewed or opened because the contents can irritate the mouth and throat. Hair-loss trials have mostly used 0.5 mg daily. Some clinicians use other regimens, such as less frequent dosing or injections into the scalp (mesotherapy); these are not FDA-approved and should only be done under a clinician’s care.
Why Half-Life Matters
The Avodart label reports a terminal elimination half-life of about 5 weeks at steady state, with blood levels reaching about 90% of steady state after 3 months and remaining detectable for 4 to 6 months after stopping. That long tail has practical consequences:
- Side effects, if they occur, may take longer to fade after stopping dutasteride than after stopping finasteride.
- The label says men taking dutasteride should not donate blood until 6 months after their last dose, so the drug is not given to a pregnant person through a transfusion.
- Men planning a pregnancy with a partner should discuss timing with a clinician.
Safety and Side Effects
Sexual side effects
Both labels list decreased libido, erectile dysfunction and ejaculation disorders as possible adverse effects, generally affecting a small minority of men in trials. The Propecia label also includes post-marketing reports of sexual dysfunction that continued after stopping the drug, as well as depression and suicidal ideation. Tell your prescriber promptly about mood changes or sexual problems.
Prostate cancer screening (PSA)
Both drugs lower prostate-specific antigen (PSA), the blood test used in prostate cancer screening. The Avodart label says dutasteride reduces PSA by about 50% within 3 to 6 months and recommends establishing a new PSA baseline after at least 3 months of treatment. The Propecia label says any confirmed increase in PSA while on the drug should be evaluated, even if it is within the normal range, and that 5-alpha-reductase inhibitors may increase the risk of high-grade prostate cancer. Tell anyone ordering a PSA test that you take one of these drugs.
Pregnancy and handling
Both drugs can cause abnormal development of the genitals of a male fetus. Finasteride is contraindicated in women who are or may become pregnant, and the label says such women should not handle crushed or broken tablets. The Avodart label similarly warns women who are or may become pregnant not to handle leaking capsules.
Breast changes
Both labels list breast tenderness and enlargement as possible effects. Report any lumps, pain or nipple discharge.
Using Either with Minoxidil
Minoxidil (Rogaine) works through a different mechanism, prolonging the growth phase of hair, and is available without a prescription. Many dermatologists combine an oral DHT blocker with minoxidil. See our minoxidil vs finasteride comparison for how the two approaches differ.
How People and Clinicians Usually Decide
- Starting treatment: finasteride is the FDA-approved option with the longest track record in hair loss, which is why it is the usual first prescription.
- Inadequate response after a fair trial: some dermatologists consider dutasteride off-label, weighing the stronger DHT suppression against the longer half-life and limited long-term hair data.
- Prostate symptoms too: a man with BPH may already be a candidate for a 5-alpha-reductase inhibitor at prostate doses; his urologist and dermatologist should coordinate.
- Worried about side effects: discuss topical minoxidil, and ask how quickly effects would reverse with each drug.
When to Talk to Your Doctor or Pharmacist
See a dermatologist before starting either drug, especially if hair loss is sudden, patchy, accompanied by scalp pain or scaling, or affects a woman, because other conditions (thyroid disease, iron deficiency, alopecia areata) may be responsible. Contact your prescriber about depression, breast lumps or nipple discharge, or persistent sexual side effects, and tell any clinician ordering a PSA test that you take a 5-alpha-reductase inhibitor.
Frequently Asked Questions
Is dutasteride stronger than finasteride?
Dutasteride blocks both forms of 5-alpha-reductase and lowers DHT more. In a 917-man trial and a three-trial meta-analysis, it increased hair count more than finasteride 1 mg over the study periods. It is not FDA-approved for hair loss.
Is dutasteride FDA approved for hair loss?
No. In the US, dutasteride (Avodart) is approved only for symptomatic BPH. Using it for hair loss is off-label.
Does dutasteride have more side effects than finasteride?
In the main head-to-head trial and the 2019 meta-analysis, rates of sexual side effects did not differ significantly. Dutasteride stays in the body much longer, so any effects may take longer to resolve after stopping.
How long does finasteride take to work?
The Propecia label says daily use for three months or more is generally needed before benefit is seen, and benefit reverses within 12 months of stopping.
Can I switch from finasteride to dutasteride?
Only with your prescriber. Switching is an off-label decision that should weigh your response, side effects and prostate screening.
Can women take finasteride or dutasteride?
Neither is FDA-approved for hair loss in women, and both are contraindicated in pregnancy because they can harm a male fetus.
Sources
- DailyMed: Propecia (finasteride 1 mg) prescribing information
- DailyMed: Avodart (dutasteride) prescribing information
- PubMed: Gubelin Harcha et al., randomized active- and placebo-controlled study of dutasteride vs finasteride in androgenetic alopecia (JAAD, 2014)
- PubMed: Zhou et al., efficacy and safety of dutasteride compared with finasteride in androgenetic alopecia: meta-analysis (2019)
- PubMed: Olsen et al., the importance of dual 5-alpha-reductase inhibition in male pattern hair loss (JAAD, 2006)
- MedlinePlus: Finasteride
Medical disclaimer: This article is for educational purposes and does not replace medical advice. Consult a licensed healthcare provider before starting any supplement, medication, or treatment — particularly if you are pregnant, breastfeeding, taking other medications, or have a diagnosed medical condition.