Propylthiouracil tablets

Last updated by Peer reviewed by Sid Dajani
Last updated Meets Patient’s editorial guidelines

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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.

The most common side-effects include stomach upset, aches and pains, a mild itchy rash, and changes to the way some things taste. These are not usually serious and soon pass.

Propylthiouracil can, however, cause serious liver problems in some people, so if you develop severe or persistent sickness, itching, any yellowing of your skin or the whites of your eyes (jaundice), or tummy pain, or if you generally feel unwell without cause, please contact your doctor for advice straightaway.

Type of medicineAn antithyroid medicine
Used forHyperthyroidism
Available asTablets

Propylthiouracil is used to treat an overactive thyroid gland (hyperthyroidism). When the thyroid gland is overactive it makes too much of a hormone called thyroxine. The extra thyroxine causes many of the body's functions to speed up. This can lead to symptoms such as losing weight, excessive sweating, feeling irritable or shaky, and diarrhoea. You also may feel tired or worried, and women may develop menstrual problems.

Although the most commonly used antithyroid medicine in the UK is called carbimazole, some people are unable to take this medicine. If so, propylthiouracil is usually used as a suitable alternative. It works by reducing the amount of thyroxine made by your thyroid gland.

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

  • If you are pregnant or breastfeeding (even though propylthiouracil could still be prescribed for you).
  • If you have any problems with the way your liver works, or if you have any problems with the way your kidneys work.
  • If you are taking any other medicines. This includes any medicines which are available to buy without a prescription, as well as herbal and complementary medicines.
  • If you have ever had an allergic reaction to a medicine.
  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about propylthiouracil, and will also provide you with a full list of the side-effects which you could experience from taking it.
  • Take the tablets exactly as your doctor tells you to. It is likely that you will be asked to take a high dose to start with, such as 4-8 tablets a day in divided doses. Your dose will then be gradually reduced to 1-3 tablets a day as your thyroid levels become more normal. Your doctor will give you the full directions for taking the tablets, and the information will also be printed on the label of the pack of tablets to remind you about what the doctor said to you.
  • Swallow your doses with a drink of water. Propylthiouracil tablets can be taken either with or without food.
  • Try to take your tablets around the same times of day each day. This will help you to remember to take propylthiouracil 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 need to have blood tests from time to time to check that you are on the correct dose and that your liver is working well. This is because propylthiouracil can occasionally cause serious liver problems.
  • Propylthiouracil should have some effect on your symptoms around three to four weeks after treatment starts. Your thyroid hormone levels should be stabilised within four to eight weeks. Continue to take the tablets for as long as you are advised to do so by your doctor.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with propylthiouracil. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common propylthiouracil side-effects
What can I do if I experience this?
Feeling sick (nausea) or being sick (vomiting), stomach upsetStick to simple foods - avoid rich or spicy food
Headache, muscle aches and painsDrink plenty of water and ask your pharmacist to recommend a suitable painkiller. If the aches continue, let your doctor know
Changes in taste, feeling tired, mild skin rash and itchingDiscuss 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 you should let your doctor know about it straightaway:

  • Being sick (vomiting).
  • Severe itching.
  • Urine which is a darker colour than normal.
  • Pain in your tummy (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 the tablets, speak with your doctor or pharmacist for further advice.

  • 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.

If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.

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.

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