Finasteride vs Dutasteride for Hair Loss: How They Compare
Both block the conversion of testosterone to DHT. Finasteride is FDA-approved for male pattern hair loss; dutasteride is stronger and longer-acting but not FDA-approved for hair loss in the US. Here is how they compare.
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Short answer: dutasteride blocks DHT more completely than finasteride, and in a 24-week trial in 917 men a 0.5 mg daily dose improved selected hair measures more than 1 mg of finasteride. But finasteride is the one FDA-approved for male pattern hair loss; dutasteride is approved in the US for an enlarged prostate, stays in the body for weeks after stopping, and has less long-term hair-loss data. Both are prescription medicines with similar side-effect warnings, so the choice belongs with a clinician.
How they work
Both are 5-alpha reductase inhibitors: they reduce the conversion of testosterone to DHT, the hormone that drives pattern hair loss. Finasteride mainly blocks one form of the enzyme (type II); dutasteride blocks both type I and type II. Dutasteride prescribing information DHT and hair loss
Side-by-side comparison
| Finasteride | Dutasteride | |
|---|---|---|
| US approval | Approved for male pattern hair loss at 1 mg source | Approved for an enlarged prostate, not for hair loss source |
| Enzymes blocked | Type II | Types I and II |
| Time in the body after stopping | Short | Long; about five weeks to clear half, with blood-donation deferral for six months |
| Head-to-head evidence | 1 mg daily was the comparator source | 0.5 mg daily improved selected measures over 24 weeks |
| Use in women | Must not be used by anyone who is or may become pregnant | Same caution |
What the head-to-head trial found
A randomized trial in 917 men aged 20 to 50 compared several dutasteride doses with finasteride 1 mg and placebo over 24 weeks. Dutasteride 0.5 mg improved selected hair-count and photographic measures compared with finasteride. Dutasteride vs finasteride trial
The trial was relatively short and industry-sponsored, so it does not settle long-term benefit or safety differences.
Side effects and safety warnings
- Sexual side effects such as lower libido, erectile problems and ejaculation changes are listed for both. Side effects of finasteride
- Mood changes. UK regulators have strengthened warnings about psychiatric side effects, including depression, and sexual dysfunction. MHRA safety update
- PSA tests. Both lower PSA results, so tell whoever orders a prostate test that you take one. About finasteride
- Pregnancy. Neither should be used by anyone who is or may become pregnant. Propecia prescribing information
Topical finasteride
Topical finasteride sprays have been tested in trials, but the FDA has warned about risks from compounded topical finasteride products, whose strength and quality can vary. Ask where any topical product comes from and how it is made. Topical finasteride trial FDA alert on compounded topical finasteride
Questions to ask your prescriber
- Is my hair loss confirmed as pattern hair loss, and how far has it progressed?
- Why this medicine and dose rather than the alternative?
- What side effects should I watch for, and what should I do if they happen?
- How long should I take it before we review the result, and how will we measure it?
- What happens to my hair if I stop?
- Do I need to tell anyone before a PSA test or before donating blood?
- Should I combine it with minoxidil?
Quick answers
Can I switch from finasteride to dutasteride?
Some clinicians do this when finasteride has not helped enough, but it is an off-label use of dutasteride in the US and should be decided with a prescriber who knows your history.
Do the side effects go away if I stop?
For most people, side effects resolve after stopping, but some report persistent symptoms. Dutasteride takes much longer to leave the body than finasteride.
Can I use minoxidil with finasteride or dutasteride?
Yes, they are often combined because they work in different ways. Discuss the plan with your prescriber.
Can women take finasteride or dutasteride?
They must not be used by anyone who is or may become pregnant. Specialists occasionally use them for some women after menopause; this is a decision for a dermatologist.