Sooner or later, a thyroid patient will pick up a bottle of cough remedy or nasal spray and find written on the package that "if you have a thyroid problem, ask your doctor before taking this medication."
Unfortunately, there is no simple set of guidelines that will ensure medication safety for all people with thyroid problems. A drug may interact not only with your thyroid but with other medications you may be taking and with other conditions known best to your doctor. The best course of action if you see that warning on a label is to ask your physician for advice.
There are some rules of thumb, however, that can give patients a general idea of what medications they should avoid.
If you are hyperthyroid, you may have a fast pulse rate, nervousness, and shakiness. If you add a medication which can increase the heart rate even further, you may worsen your condition. Many over-the-counter cold remedies contain decongestants which can speed up your heart and cause nervousness. Therefore, if you are actively hyperthyroid, even if your condition is partially controlled by medication, you should avoid these cold medicines as well as other stimulants of all sorts. This means you should not drink too much coffee, tea, or cola, since caffeine can also cause an increase in the pulse rate.
Once hyperthyroidism has been controlled, however, through radioactive iodine treatment, a thyroid operation, or anti-thyroid drug therapy, and you know your thyroid blood level is normal, cold medications can usually be safely taken according to the manufacturer's instructions. You are not at lifelong risk for hyperthyroidism or other thyroid problems simply because you once had one, and there should be no problem with cough or cold medicines you took before you had a thyroid condition.
Iodine is another matter. Iodine may be encountered in, among other sources, kelp from health food stores, cough remedies, a dye used by radiologists to make special x-rays such as arteriograms or kidney x-rays, or a new heart medicine called amiodarone. …