A 5-alpha-reductase inhibitor for an enlarged prostate
Dutasteride
A 5-alpha-reductase inhibitor that shrinks an enlarged prostate over time to improve urinary flow in men.
What is Dutasteride?
Dutasteride is a 5-alpha-reductase inhibitor used to treat benign prostate enlargement in men. It lowers the hormone that drives prostate growth, so the gland gradually shrinks and urinary symptoms improve. It works slowly over months, lowers PSA blood-test results, and must not be handled by women who are or could become pregnant.
Education and reference only. This is a plain-language guide to Dutasteride — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Dutasteride is a 5-alpha-reductase inhibitor used in men with benign prostatic hyperplasia (an enlarged prostate). It reduces the size of the prostate gland over time, which eases urinary symptoms such as a weak stream, hesitancy and frequent night-time visits. It is sometimes combined with an alpha-blocker (such as tamsulosin) for a fuller effect. It works gradually, so improvement is measured over months rather than days.
How it works
The prostate grows under the influence of a powerful male hormone called dihydrotestosterone (DHT), which the body makes from testosterone using an enzyme called 5-alpha-reductase. Dutasteride blocks this enzyme, lowering DHT levels throughout the body. With less DHT, the prostate gradually shrinks, relieving pressure on the urethra and improving urine flow. Because it acts on hormone levels, the benefit builds slowly over several months.
Company & origin
Originated / developed by: Originally developed by GlaxoSmithKline and now available as a generic medicine..
A 5-alpha-reductase inhibitor introduced in the 2000s to shrink an enlarged prostate and ease urinary symptoms.
What it treats
Conditions Dutasteride is used for
Practical use
How to take Dutasteride
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Swallow the capsule whole with water — do not chew or open it, as the contents can irritate the mouth and throat.
- Take it at around the same time each day; it can usually be taken with or without food.
- Be patient, as it can take several months of regular use before the full benefit on urinary symptoms is felt.
- Keep taking it unless told otherwise, because stopping allows the prostate to enlarge again over time.
- If you miss a dose, skip it and take the next one as usual — do not take two to catch up.
Weighing it up
Advantages & disadvantages of Dutasteride
Advantages
- Gradually shrinks an enlarged prostate, easing urinary symptoms and lowering the chance of future problems such as retention.
- Can be combined with an alpha-blocker for men who need more than one type of treatment.
- Taken once a day and available as a generic medicine.
Disadvantages
- Works slowly, so it can take months before symptoms clearly improve.
- Can reduce sex drive and cause erection or ejaculation problems in some men.
- Lowers PSA results and is hazardous in pregnancy, so it needs careful handling and clear communication with clinicians.
Practical use
Good to know
Dutasteride works slowly, so it can take several months to feel the full benefit, and stopping it allows the prostate to grow again. It lowers the PSA blood test used in prostate-cancer screening, so your clinician needs to know you take it when interpreting results. It can reduce sex drive and cause other sexual side effects in some men. Importantly, it can harm a developing baby, so women who are or could become pregnant should not handle leaking capsules, and men taking it should not donate blood.
Who should not take it / use with caution
- Women, children, and anyone who has had a serious allergic reaction to it or to similar medicines (such as finasteride).
- Women who are pregnant or could become pregnant must not handle leaking or broken capsules, as it can harm a developing baby.
- Men with significant liver disease should use it only with specialist advice.
Monitoring
- PSA blood tests are interpreted with the knowledge that dutasteride roughly halves the result.
- Review of urinary symptoms and prostate size to judge how well it is working.
- Watch for and report any breast changes or new low mood.
Side effects
- Reduced sex drive, difficulty getting an erection, or problems with ejaculation.
- Breast tenderness or enlargement.
- Rarely, mood changes including low mood, and changes in the breast that should be reported promptly.
Key interactions
- Certain medicines that strongly affect the liver (such as some antifungals, HIV medicines and the antibiotic clarithromycin) can raise its levels.
- When combined with the alpha-blocker tamsulosin, dizziness and low blood pressure on standing can be more noticeable.
- Tell any clinician you take it, as it lowers PSA results used in prostate-cancer assessment.
Available as: Capsules, including a combination capsule with tamsulosin.
Answers
Dutasteride: frequently asked questions
How long before dutasteride starts to work?
It works gradually by shrinking the prostate, so it can take several months before urinary symptoms clearly improve. If you also take an alpha-blocker, that part may help sooner. Keep taking it as prescribed even before you notice a difference.
Why does dutasteride affect my PSA test?
Dutasteride lowers the PSA blood test result, roughly halving it. This matters because PSA is used to help detect prostate cancer, so always tell the clinician taking the test that you are on dutasteride, so they can interpret the figure correctly.
Can my partner handle my dutasteride capsules?
Women who are pregnant or could become pregnant should not handle leaking or broken capsules, because the medicine can harm a developing baby. Intact capsules swallowed whole are the safe way to take it; do not cut or open them.
Will dutasteride affect my sex life?
Some men notice reduced sex drive or difficulty with erections or ejaculation. These often settle but can persist; if they bother you, discuss it with your clinician, who can review your treatment.
Can I give blood while taking dutasteride?
No. Men taking dutasteride are asked not to donate blood while on it and for a period after stopping, so that the medicine cannot reach a pregnant woman through a transfusion. Mention it if you are asked about medicines at a blood-donation session.
The wider class
About 5-alpha-reductase inhibitors
Dutasteride belongs to the 5-alpha-reductase inhibitors class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF: Dutasteride.
- electronic Medicines Compendium (SmPC): Avodart (dutasteride).
- NICE CKS: Benign prostate enlargement.
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