The main antithyroid medicines are the thionamides: Methimazole
(such as Northyx, Tapazole)Propylthiouracil
(such as Propyl-Thyracil)
Carbimazole (not currently available in the United States)
can interfere with how your body uses this medicine. If you smoke, talk to your doctor about how to
These drugs interfere with the thyroid gland’s ability to make hormones and with the peripheral tissues' ability to use it. These medicines 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 medicine your body absorbs into the bloodstream. Therefore, always take your medicine 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 medicine only needs to be taken once daily. Propylthiouracil is usually taken three times a day. This medicine 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: RashItchy skinFeverAchy jointsNausea
These side effects may go away spontaneously or after switching to another antithyroid medicine.
Important, but rare side effects include: Agranulocytosis
(a deficiency of white blood cells caused by bone marrow toxicity)—This condition goes away when the medicine is stopped.
(liver damage)—This is seen more often with propylthiouracil than with methimazole.
Since agranulocytosis 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 medicine. If you notice a high fever or serious infection while taking antithyroid medicine, tell your doctor right away. The medicine will need to be stopped if tests show agranulocytosis.
Common names include: Propranolol
(such as Inderal)Atenolol
(such as Tenormin)Metoprolol
(such as Lopressor, Toprol)
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 right away, it can cause a dangerous increase in blood pressure.
Possible side effects include:
Bronchospasm or worsening of
chronic obstructive pulmonary disease
DizzinessDrowsinessLoss of sex driveDifficulty sleeping
Many of these side effects may go away spontaneously as your body gets used to the medicine. Any breathing problems, however, can be serious. Report them to your doctor. Your medicine may need to be stopped or substituted.