"Warning: do not take this medication if you have thyroid disease."

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. No matter where it comes from, iodine can cause big trouble for thyroid patients, even those with "cured" hyperthyroidism or simply a nodular goiter.

Following a dose of iodine, there may be either a marked increase in thyroid hormone release and hyperthyroidism or a sudden drop in thyroid hormone production and hypothyroidism. Therefore, unlike stimulant drugs and caffeine, big doses of iodine should be avoided in any form. If iodine exposure is medically necessary, be sure your doctor is aware of your underlying thyroid disorder.

One other possible source of iodine is multivitamin preparations. Once-a-day vitamins containing 100 micrograms (0.1 milligrams) of iodine per capsule are not a cause for concern, but larger doses of iodine may cause a problem.

RELATED ARTICLE: Books about thyroid disorders recommended by The Thyroid Foundation of America

Baskin, H. Jack. How Your Thyroid Works. 4th Edition. Adams Press, Chicago. 1995. $8.00 postpaid.

Hamburger, Joel I. The Thyroid Gland: A Book for Thyroid Patients. 7th Edition. Published privately by Dr. Hamburger. 1991. $8.00 postpaid.

Wood, Lawrence C., David S. Cooper, and E. Chester Ridgway. Your Thyroid: A Home Reference. 3rd Edition. Ballantine Books, New York. 1995. $8:00 postpaid.

To order any of the above books, send a check for the full amount payable to: The Thyroid Foundation of America, Inc., Ruth Sleeper Hall-RSL 350, 40 Parkman St., Boston, MA 02114-2698. Residents of Massachusetts include 5% sales tax.

Bayliss, R.I.S. and W.M.G. Tunbridge. Thyroid Disease: The Facts. 2nd Edition. Oxford University Press. New York. 1991.

Surks, Martin I. The Thyroid Book: What Goes Wrong and How to Treat It. Consumer Reports Books. Yonkers, NY. 1994.

The two books above are not available through TFA. Please check your local bookstore or library.