Carbimazole warning sheet - Investigation protocol

Carbimazole warning sheet for health care professionals

This patient is taking carbimazole/PTU for their thyroid condition.


If they have developed a rash, please consider switching to an alternative agent. If they are taking carbimazole, please prescribe propylthiouracil (PTU) in place of the carbimazole - the dose of PTU is 10 times the dose of carbimazole (for example 20mg carbimazole = 200mg PTU). PTU doses should be divided and given two or three times a day (for example 100mg bd). Antihistamines may be given for associated pruritus if necessary.

If the patient has had both carbimazole and PTU, or you are concerned about the patient or require further information, please contact the endocrinolgy doctor on call.

Sore throat, fever or mouth ulcers

 If the patient attends with a fever, flu like symptoms, mouth ulcers or a sore throat, this may indicate the development of neutropaenia. Please ensure that they have stopped their medication, and check their full blood count urgently. If this is normal, the patient can continue the drug. If the white cell count is low, please contact the endocrine team immediately.