Antithyroid Medications
The main antithyroid medications are the thionamides:
- Methimazole
- Propylthiouracil
-
Carbimazole (not currently available in the United States)
- Note: Smoking
can interfere with how your body uses this medication. If you smoke, talk to your doctor about how to
quit.
These drugs interfere with the thyroid gland’s ability to make hormones and with the peripheral tissues' ability to use it. These medications can be taken with meals or on an empty stomach. It is important to always take them at the same time in relation to meals. Food affects the amount of medication your body absorbs into the bloodstream. Therefore, always take your medication with meals or always take it on an empty stomach.
Methimazole is the preferred drug of choice because of its reduced risk of adverse events. Another plus is that the medication only needs to be taken once daily. Propylthiouracil is usually taken 3 times a day. This medication is considered the second choice. But, if you are in your first trimester of pregnancy or if you cannot take methimazole, your doctor may have you take propylthiouracil. Carbimazole is yet another option to treat hyperthyroidism.
Possible side effects include:
- Rash
- Itchy skin
- Fever
- Achy joints
- Nausea
These side effects may go away spontaneously or after switching to another antithyroid medication.
Important, but rare side effects include:
- Neutropenia
(a deficiency of white blood cells caused by bone marrow toxicity)—This condition goes away when the medication is stopped.
- Hepatitis
(liver damage)—This is seen more often with propylthiouracil than with methimazole.
Since neutropenia is rare and is not predictable by doing blood tests, your doctor must rely on your medical history to determine if this complication may occur. Many doctors obtain a baseline blood count and liver function tests before starting the medication. If you notice a high fever or serious infection while taking antithyroid medication, tell your doctor right away. The medication will need to be stopped if tests show neutropenia.
Beta-blockers
Common names include:
- Propranolol
- Atenolol
- Metoprolol
Beta-blockers slow the heart rate. They are also helpful for reducing a rapid heartbeat, anxiety, or tremors. These are all symptoms that can occur with hyperthyroidism.
Do not stop taking a beta-blocker without checking with your doctor first. If you stop suddenly, it can cause a dangerous increase in blood pressure.
Possible side effects include:
Many of these side effects may go away spontaneously as your body gets used to the medication. Any breathing problems, however, can be serious. Report them to your doctor. Your medication may need to be stopped or substituted.
