Good morning and cheers for letting us know your query. Congratulations on your pregnancy and I’m sorry to hear your situation. Antithyroid drugs such as carbimazole are used to treat an overactive thyroid gland or known as hyperthyroidism or thyrotoxicosis.

When the thyroid gland produces too much thyroid hormone, it can cause most of your bodily functions to speed up, and will lead to symptoms like losing weight, shaky or felling irritable, sweating, weight loss but increase appetite and diarrhoea. You also can feel tired or lethargic, and develop menstrual problems before or after pregnancy.

Carbimazole is the most commonly used drugs for over active thyroid gland. It acts by decreasing the amount of thyroid hormones which is produced by thyroid glands. Common side effects of carbimazole will include nausea, stomach pain, headache, joint pain, skin rash or itching, or hair loss or mouth ulcers.

If you have over active thyroid gland, you will still need to take carbimazole drugs during your pregnancy. This drug can cross the placenta so the lowest dose should be prescribed so that the baby is less likely to be affected. But if you are already on Carbimazole when you are pregnancy you should change to Propylthiouracil which is an antithyroid medication as soon as possible.

PTU is the drug of choice when trying to become pregnant and in the first 3 months of pregnancy. If PTU is not available then carbimazole can be used. Very rarely, anti thyroid drugs can cause side effects in pregnancy, such as agranulocytosis which is lowering of the number of white blood cells and severe liver disease.

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