What are the side effects?
In common with all medications, dutasteride can cause side effects in some people.
Common side effects (affecting 1 in 10 men):
- erectile dysfunction
- decreased libido (sex drive)
- ejaculation problems
- breast enlargement or tenderness
Uncommon side effects (affecting 1 in 100 men):
- heart failure - symptoms include shortness of breath, extreme fatigue and swelling in legs and ankles
- hair loss or hair growth
Side effects where the frequency is not known:
- feeling depressed
- testicular swelling and pain
Dutasteride can cause an allergic reaction which can be serious if left untreated, so if you notice any of the following symptoms when taking the medicine, stop taking it and get medical help straight away:
- skin rash (sometimes itchy)
- swelling of the face, lips, eyelids, arms or legs
Certain medicines also react with dutasteride and can make side effects more likely to occur. Tell your doctor before taking dutasteride if you are taking any of the following medications:
- alpha-blockers (for enlarged prostate or high blood pressure).
- certain high blood pressure medicines
- HIV treatment
- treatment for fungal infections
- certain antidepressants
Dutasteride is to be taken by men only and must not be taken by women, children or adolescents. Broken capsules must not be handled by pregnant women, as the active ingredient can be absorbed through the skin and can cause birth defects in male babies. If your partner is pregnant a condom must be used during sex. This is because dutasteride can be carried in semen and it could affect the normal development of a male baby.
Dutasteride has been shown to reduce sperm count, semen volume and the movement of sperm, which could affect male fertility. Dutasteride is also not recommended for use by men with serious liver disease.
It can also cause male breast enlargement (gynaecomastia) and tenderness. You should see your doctor if this bothers you and if you notice lumps in the breast or discharge from your nipple. These could be signs of breast cancer.
If you are allergic to peanuts or soya, you mustn’t use dutasteride as it contains lecithin from soya, which could contain soya oil.