Key points
- ◆A dual inhibitor (types I and II) that reduces DHT by more than 90%.
- ◆More potent than finasteride, with a similar adverse-effect profile.
- ◆Very long half-life: it remains in the body for weeks after stopping.
- ◆Off-label hair use in much of Europe; approved for alopecia in some countries.
- ◆Absolutely contraindicated in pregnancy.
Description
Dutasteride is an oral drug from the family of 5-alpha-reductase inhibitors. Unlike finasteride, it blocks both isoforms of the enzyme (types I and II), so it reduces DHT more intensely. It is approved for benign prostatic hyperplasia and is used in androgenetic alopecia, with official approval in some countries.
Indications
- Benign prostatic hyperplasia (0.5 mg/day).
- Androgenetic alopecia: off-label use in much of Europe, although it is approved for this indication in countries such as South Korea or Japan.
- Hair mesotherapy (local application, off-label).
Mechanism of action
Dutasteride inhibits both isoenzymes of 5-alpha-reductase (types I and II), whereas finasteride only blocks type II. As a result, it reduces circulating DHT by more than 90%, compared with 60-70% for finasteride.
Mechanism of action
Inhibiting 5-α-reductase lowers DHT and slows follicle miniaturisation.
Usual dosage
The usual dose is 0.5 mg per day orally. Its half-life is very long (around 5 weeks), so the drug persists in the body for months after stopping it.
Side effects
Its adverse-effect profile is similar to that of finasteride, although potentially somewhat more marked because of its greater potency:
- Sexual dysfunction: decreased libido, erectile dysfunction, ejaculation disorders.
- Gynaecomastia.
- As with other 5-alpha-reductase inhibitors, mood changes and depression have been described; monitor and stop if relevant psychiatric symptoms occur (class warning reinforced by the EMA/CMDh, 2024-2025).
It also reduces PSA by around 50%, a fact to consider in prostate screening.
Contraindications
- Pregnant women or women of childbearing age (teratogenic effect).
- Hypersensitivity to the drug or to other 5-alpha-reductase inhibitors.
- Blood should not be donated until at least 6 months after stopping treatment, because of its long half-life.
Pregnancy and breastfeeding
Contraindicated during pregnancy: like finasteride, it can affect the genital development of a male foetus. Pregnant women must not handle the capsules. Because of its long half-life, these precautions must be maintained for an extended period.
Important interactions
It is metabolised by CYP3A4. Potent inhibitors of this enzyme (for example, certain antifungals or antiretrovirals) can increase its levels and prolong its effect.
Level of scientific evidence
Level of evidence: high for prostatic hyperplasia and moderate-high for androgenetic alopecia, with clinical trials showing efficacy equal to or greater than finasteride. Its hair use is off-label except in countries where it is expressly approved.
Frequently asked questions
Is dutasteride better than finasteride for hair?
It reduces DHT more intensely and in some studies shows greater efficacy, but it may also be associated with more adverse effects. The choice must be individualised with the physician.
Why can't I donate blood while taking it?
Because of its long half-life, the drug remains in the blood for months. Donating could expose a pregnant recipient to a teratogenic risk.
How long does it take to be eliminated from the body?
Its half-life is about 5 weeks, so it can be detected in the body several months after the last dose.
Is it approved for alopecia?
It depends on the country. In much of Europe it is used off-label for alopecia, while in countries such as South Korea or Japan it has a specific indication.
References
- Gubelin Harcha W, et al. A randomized, active- and placebo-controlled study of dutasteride vs finasteride in men with androgenetic alopecia. J Am Acad Dermatol. 2014.
- European Medicines Agency (EMA). Summary of product characteristics for dutasteride 0.5 mg.
- EMA/CMDh. Finasteride and dutasteride: risk of suicidal ideation and mood changes (referral outcome). 2024. https://www.ema.europa.eu/en/medicines/human/referrals/finasteride-dutasteride-containing-medicinal-products
- Zhou Z, et al. Dutasteride versus finasteride in androgenetic alopecia: a meta-analysis. 2019.
- Kanti V, et al. Evidence-based (S3) guideline for the treatment of androgenetic alopecia. J Eur Acad Dermatol Venereol (EADV). 2018. doi:10.1111/jdv.14624.
Clínica Valorian's view
At Clínica Valorian we reserve dutasteride for selected cases of androgenetic alopecia, usually when the response to finasteride is insufficient. Given its greater potency and long half-life, we insist on complete patient information and careful follow-up, and we rule it out entirely in women who could become pregnant.
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This fact sheet is for information and medical education purposes only. It does not replace a medical consultation or an individual prescription.