How does Carbimazole work?
Carbimazole is converted to an active agent called methimazole in the body. Methimazole acts on thyroid gland and reduces its overactivity.
How is Carbimazole taken?
Treatment dose is usually prescribed by your doctor, depending on the thyroid blood test. It is started at high dose ranging between 20 to 60 mg per day. Carbimazole is to be taken once a day. It is preferable to take the tablet at the same time every day. The dose is kept at these high levels until thyroid activity returns to normal. Then the dose is progressively reduced till it is stopped. Usually total duration of treatment is approximately 18 months.
What are the side effects?
In general, Carbimazole is safe, but some patients can develop side effects. These include;
- Headache, nausea, joint pains, and stomach upset.
- Skin rash. This can occur in 1 in 50 cases. Contact your doctor if this happens.
- In rare cases, Carbimazole can reduce the activity of bone marrow. This can reduce the production of protective body cells. This can lead to infection. Usually, this presents a severe sore throat, mouth ulcers, and fever. If any of these symptoms develop, contact your doctor immediately and stop the medication. The doctor will do your blood count. Bone marrow activity will recover in 1 to 2 weeks.
Can Carbimazole be used in pregnancy or breastfeeding?
Yes, Carbimazole can be used in pregnancy and breastfeeding. However, it is advised to discuss with your doctor if you are planning pregnancy or as soon as you know that you are pregnant. In the first trimester, it is preferred to change Carbimazole to another anti-thyroid tablet called Propylthiouracil. Carbimazole can cross the placenta and in very rare cases can affect the skin or nail or finger of the baby in first trimester. Carbimazole is usually continued in second and thirst trimester as it is safe for both mother and baby. In general, lowest possible dose of Carbimazole is taken. It is preferable to keep the dose of Carbimazole below 20 mg. However, the doctor will decide with you the best possible dose given the risk and benefit.