This section of the website is for UK men who have already been prescribed Propecia. If you are a healthcare professional, visit the HCP section of the site. This website is not intended to replace the advice of a healthcare professional. You should consult your doctor or another suitably trained healthcare provider when considering what type of treatment is most appropriate for you.

Side effects

Like all medicines, Propecia (finasteride) can cause side effects, although not everybody gets them. It is well tolerated in men, however the following side effects may happen with this medicine:

Allergic reactions

If you have an allergic reaction, stop taking it and see your doctor straight away. The signs may include:

  • Skin rashes, itching, or lumps under your skin (hives)
  • Swelling of lips, face, tongue or throat
  • Difficulty swallowing
  • Breathing difficulties

Other side effects may include:

  • You may be unable to have an erection (impotence)
  • You may have less desire to have sex
  • You may have problems with ejaculation, for example a decrease in the amount of semen released during sex. This decrease in the amount of semen does not appear to affect normal sexual function.

These side effects above may disappear after a while if you continue taking Propecia. If these symptoms persist, they usually resolve after stopping Propecia.

Other side effects reported in men are:

  • Breast swelling or tenderness. Breast cancer has been reported in men taking Propecia during clinical trials and in the post-marketing period. Patients should promptly report to their physician any changes in their breast tissue such as lumps, pain, breast enlargement or nipple discharge
  • Palpitations (feeling your heartbeat)
  • Changes in the way your liver is working, which can be shown by a blood test
  • Pain in the testicles
  • Persistent difficulty having an erection after discontinuation of treatment
  • Persistent decrease in sex drive after discontinuation of treatment
  • Persistent problems with ejaculation after discontinuation of treatment
  • Infertility has been reported in men who took finasteride for a long time and had other risk factors that may affect fertility. Normalisation or improvement of seminal quality has been reported after discontinuation of finasteride. Long-term clinical studies about the effects of finasteride on fertility in men have not been conducted
  • Depression

Tell your doctor or pharmacist immediately about these or any other unusual symptoms, it will help if you make a note of what happened, when it started and how long it lasted. For more information on Propecia, please ask your doctor.

Merck Sharp & Dohme Limited Registered Office: Hertford Road, Hoddesdon, Hertfordshire, EN11 9BU.
A company registered in England and Wales. Company Registration Number: 820771

GB-PRO-00005 | Date of preparation: January 2019
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