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Keep your regular appointments with your doctor so that your condition can be monitored and any dose adjustments made. You will need to have regular blood tests.

Important: if you develop sickness, itching, jaundice, pain in your abdomen, or if you generally feel unwell, contact your doctor straightaway.

Type of medicineAntithyroid medicine
Used forHyperthyroidism
Available asTablets

Antithyroid medicines like propylthiouracil are used to treat hyperthyroidism (an overactive thyroid), which is also known as thyrotoxicosis. When your thyroid gland produces too much thyroid hormone it can lead to symptoms such as losing weight, sweating, feeling irritable or shaky, and diarrhoea. You also may feel tired or worried, and develop menstrual problems.

The most commonly used antithyroid medicine in the UK is carbimazole, but some people are unable to take this medicine. Propylthiouracil is often a suitable alternative. It works by reducing the amount of thyroid hormones your thyroid gland makes.

Propylthiouracil may be used alone or together with other treatments for hyperthyroidism. It is also used in preparation for thyroidectomy (removal of part or all of your thyroid gland during surgery), and before radio-iodine treatment.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking propylthiouracil it is important that your doctor or pharmacist knows:

  • If you are pregnant, trying for a baby or breast-feeding.
  • If you have liver or kidney problems.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • If you have ever had an allergic reaction to a medicine.
  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The leaflet will give you more information about propylthiouracil and a full list of side-effects which you may experience from taking it.
  • Take this medicine exactly as your doctor tells you to. It is likely you will be asked to take a higher dose to start with, and then your dose will be reduced as your thyroid levels become normal. Your doctor will tell you how many tablets to take each day and how often to take them, and this should also be printed on the label of the pack to remind you.
  • Try to take your doses at the same times each day, as this will help you to remember to take them regularly.
  • If you forget to take a dose, take it as soon as you remember (unless it is nearly time for your next dose, in which case leave out the missed dose). Do not take two doses together to make up for a forgotten dose.
  • Try to keep your regular appointments with your doctor. This is so your doctor can check on your progress and any dose adjustments can be made. You will also need to have blood tests from time to time to check that your liver is working well. This is because propylthiouracil can occasionally cause serious liver problems.
  • Treatment with propylthiouracil is usually long-term unless you are scheduled to receive other treatment. Continue to take the tablets unless you are advised otherwise by your doctor.
  • Before having any kind of medical treatment, including dental or emergency treatment, tell the person carrying out the treatment that you are taking propylthiouracil.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. These usually improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following side-effects continue or become troublesome.

Most common propylthiouracil side-effects
What can I do if I experience this?
Feeling or being sick, stomach upsetStick to simple foods - avoid rich or spicy food
HeadacheAsk your pharmacist to recommend a suitable painkiller
Changes in taste, feeling tired, mild skin rash and itching, muscle aches and painsDiscuss these with your doctor if they become troublesome

Important: propylthiouracil can cause serious liver problems in some people. If you develop any of the following, let your doctor know straightaway:

  • Feeling sick.
  • Itching.
  • Urine which is a darker colour than normal.
  • Pain in your abdomen.
  • Any yellowing of your skin or the whites of your eyes (jaundice).
  • Generally feeling unwell.

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital at once. Take the container with you, even if it is empty.

If you buy any medicines, check with a pharmacist that they are safe to take with your other medicines.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine, ask your pharmacist.

Further reading & references

  • British National Formulary; 64th Edition (Sep 2012) British Medical Association and Royal Pharmaceutical Society of Great Britain, London

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Dr John Cox
Document ID:
3276 (v23)
Last Checked:
Next Review:
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