Finasteride vs dutasteride: compared
Finasteride (Proscar, Propecia) and dutasteride (Avodart) both block the conversion of testosterone to DHT, shrinking an enlarged prostate. Dutasteride blocks more of the enzyme and lowers DHT further; finasteride is also approved, at a lower dose, for hair loss.
Updated October 4, 2026
At a glance
- Enzymes blocked
- Finasteride
- Type 2 of 5-alpha reductase
- Dutasteride
- Types 1 and 2
- Approved for
- Finasteride
- Enlarged prostate (5 mg); male pattern hair loss (1 mg)
- Dutasteride
- Enlarged prostate
- Time in the body
- Finasteride
- Days
- Dutasteride
- Weeks to months
- Blood donation
- Finasteride
- Wait one month after the last dose
- Dutasteride
- Wait six months after the last dose
- Generic
- Finasteride
- Yes
- Dutasteride
- Yes
Finasteride Proscar, Propecia | Dutasteride Avodart | |
|---|---|---|
| Enzymes blocked | Type 2 of 5-alpha reductase | Types 1 and 2 |
| Approved for | Enlarged prostate (5 mg); male pattern hair loss (1 mg) | Enlarged prostate |
| Time in the body | Days | Weeks to months |
| Blood donation | Wait one month after the last dose | Wait six months after the last dose |
| Generic | Yes | Yes |
How they differ
Both shrink an enlarged prostate over months and lower the risk of urinary retention and surgery, and they work similarly well for that purpose. Dutasteride lowers DHT more because it blocks both forms of the enzyme. Finasteride is the one approved for hair loss in the US, while dutasteride is approved only for the prostate.
Side effects and precautions
Both can lower sex drive and affect erections or ejaculation, and both roughly halve the PSA blood test result, so tell whoever checks your PSA. Anyone who is or may become pregnant should not handle crushed finasteride tablets or leaking dutasteride capsules, because the medicine can harm a male fetus. Dutasteride capsules are swallowed whole.
Because dutasteride lingers
Dutasteride stays in the body far longer, which is why blood donation must wait six months after the last dose, compared with one month for finasteride, and why its effects and side effects fade more slowly after stopping.
Cost
Both are inexpensive generics. For hair loss, generic finasteride 1 mg is the same medicine as Propecia.
What to expect over time
Urinary symptoms usually improve over three to six months, and the prostate keeps shrinking for longer, so these medicines are taken long term; stopping lets the prostate grow again. They are often combined with an alpha blocker such as tamsulosin for faster relief, and your prescriber will reassess after several months.
Questions for your prescriber
- Is there a reason to prefer one for my prostate?
- How long until I notice a difference?
- How will this change my PSA testing?
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Sources
Written by the Script Unlock editorial team from the sources above. It is general information, not advice for you or your pet; your prescriber decides which medicine is right.
Script Unlock is a marketplace that lets licensed pharmacies quote a cash price on your prescription. It does not prescribe, dispense or sell medication, does not process patient payments, and does not give medical advice. Always follow the instructions of your prescriber and pharmacist and read the medication guide supplied with your medicine.