What is dutasteride?
Dutasteride is a prescription-only medicine used off-label to treat male pattern hair loss. It belongs to the same class of drugs as finasteride, known as 5-alpha reductase inhibitors, but works more broadly by blocking both type 1 and type 2 forms of the enzyme responsible for converting testosterone into DHT.
Dutasteride is also licensed at the same 0.5 mg dose under the brand name Avodart for the treatment of an enlarged prostate (benign prostatic hyperplasia). For hair loss, it is prescribed off-label, meaning it is used outside its formal licence for a purpose supported by clinical evidence but not yet granted a specific hair loss indication by the MHRA. Your prescriber will discuss this with you as part of your consultation.
How does dutasteride work?
Male pattern hair loss is driven by dihydrotestosterone (DHT), a hormone derived from testosterone by the action of two enzymes: type 1 and type 2 5-alpha reductase. In men with a genetic sensitivity to DHT, the hormone binds to receptors in hair follicles and causes them to progressively miniaturise, producing thinner and shorter hairs until growth eventually stops altogether.
Dutasteride inhibits both forms of the 5-alpha reductase enzyme. This dual blockade reduces DHT levels in the scalp by approximately 90 to 95%, compared to around 60 to 70% with finasteride. The more complete suppression of DHT is the key pharmacological difference between the two treatments and is thought to account for dutasteride's stronger effect in clinical studies.
With DHT significantly reduced, the miniaturisation process slows or stops. Over time, follicles that have not yet been permanently lost may begin to recover, and new hair growth can occur in areas that have recently thinned. As with finasteride, results require consistent daily use over several months before becoming visible.
What are the benefits of using dutasteride?
Dutasteride offers several advantages for men with male pattern hair loss, particularly for those who have not achieved sufficient results with finasteride.
More complete DHT suppression. By blocking both type 1 and type 2 5-alpha reductase, dutasteride reduces scalp DHT levels by up to 95%, compared to approximately 65% with finasteride.
Strong evidence for hair regrowth. Clinical studies comparing dutasteride 0.5 mg directly with finasteride 1 mg have shown dutasteride to produce greater increases in hair count and hair weight after 24 weeks of treatment.
Once-daily convenience. Dutasteride is taken as a single 0.5 mg capsule each day, with no special timing or dietary requirements.
An option when finasteride is insufficient. For men who have tried finasteride without adequate results, dutasteride offers a clinically supported alternative with a stronger mechanism of action.
Who can use dutasteride?
Dutasteride 0.5 mg is prescribed off-label for adult men experiencing male pattern hair loss. A consultation is required before it can be prescribed, and your prescriber will assess your suitability as part of the DoktorABC online consultation.
Dutasteride may be suitable for you if:
- You are a man aged 18 or over
- You are experiencing male pattern hair loss (a receding hairline, thinning at the crown, or both)
- You have no contraindications identified during your online consultation
- You have previously tried finasteride without adequate results, or your prescriber considers dutasteride the most appropriate first-line option for you
Dutasteride is not suitable if:
- You are a woman. Dutasteride is not for use in women. It carries a significant risk of causing birth defects and must not be taken by women who are pregnant or may become pregnant.
- You are under 18 years of age
- You have liver disease, as dutasteride is extensively metabolised by the liver
- You have a known allergy to dutasteride, other 5-alpha reductase inhibitors, or any component of the capsule
- You have been diagnosed with prostate cancer
How to take dutasteride?
Dutasteride 0.5 mg is taken once daily by mouth. The capsule should be swallowed whole and must not be chewed or opened, as the contents can irritate the lining of the mouth and throat. It can be taken with or without food, at any time of day that suits your routine.
If you miss a dose: Take it as soon as you remember. If it is almost time for your next dose, skip the missed one and continue as normal. Do not take two capsules to make up for a missed dose.
How long before you see results: Most men notice that hair shedding has slowed within the first three months. Visible improvements in hair density or regrowth typically become apparent between six and twelve months of daily use.
How long to continue treatment: Dutasteride works only while it is being taken. If treatment is stopped, DHT levels will return to baseline and hair loss is likely to resume within six to twelve months. Many men choose to continue long-term to maintain their results.
Do not exceed the prescribed dose. Taking more than the recommended amount will not improve results and increases the risk of side effects.
Precautions and interactions
Liver function. Dutasteride is extensively metabolised by the liver and has a half-life of approximately five weeks, meaning it accumulates in the body over time. Men with liver disease or significantly impaired liver function should not take dutasteride.
Prostate health. Like finasteride, dutasteride reduces PSA levels by around 50%. Inform any doctor ordering a PSA test that you are taking dutasteride, as unadjusted results could mask early signs of prostate cancer.
Drug interactions. Dutasteride is metabolised by the CYP3A4 enzyme pathway. Medicines that inhibit this pathway, including some antifungals (such as ketoconazole) and certain HIV treatments, can increase dutasteride levels in the blood. Always inform your prescriber of all other medications, supplements, and over-the-counter treatments you are taking.
Long half-life. Dutasteride remains detectable in the blood for up to six months after stopping treatment. This has implications for blood donation, fertility considerations, and the persistence of any side effects after discontinuation.
Donation of blood. Men taking dutasteride should not donate blood during treatment and for six months after stopping, to protect against the risk of dutasteride being administered to a pregnant woman through a blood transfusion.
Handling capsules. Dutasteride capsules should not be handled by women who are pregnant or may become pregnant. The active ingredient can be absorbed through the skin and may cause harm to a male foetus.
Fertility. Dutasteride has been detected in semen. Men whose partners are pregnant or trying to conceive should discuss this with their prescriber before starting treatment.
What are the side effects of Finasteride?
Like all prescription medicines, dutasteride can cause side effects, although not everyone experiences them. The side effect profile is broadly similar to finasteride, reflecting their shared mechanism of action.
Common side effects (may affect up to 1 in 10 men):
- Decreased libido (reduced sex drive)
- Erectile dysfunction
- Ejaculation disorders, including reduced ejaculate volume
- Breast tenderness or enlargement (gynaecomastia)
These effects are typically mild. In most cases they resolve during continued treatment or after stopping dutasteride. However, because dutasteride has a very long half-life, the active ingredient remains in the body for an extended period after stopping. Side effects may therefore persist for several months after treatment is discontinued.
Uncommon side effects (may affect up to 1 in 100 men):
Hypersensitivity reactions such as rash, itching, hives, or swelling of the face and lips
Localised swelling (oedema)
Dutasteride and mental health: Some reports have linked 5-alpha reductase inhibitors to mood changes, including low mood and, rarely, depression. If you notice significant changes in your mood during treatment, speak to your GP or prescriber promptly.
Dutasteride and PSA levels: Dutasteride reduces prostate-specific antigen (PSA) levels by approximately 50%. If you have a PSA test while taking dutasteride, inform your doctor so that results can be interpreted correctly.
If any side effect concerns you, contact your prescriber or GP. You can also report suspected side effects to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.
Note: The Patient Information Leaflet (PIL) in your medicine pack may differ from the PDF version on this website, as it may have been updated since packaging or the medicine may be from another brand.
