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Synthroid oral

Oral Thyroid Agents/Aluminum;Magnesium;Lanthanum;Simethicone

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

Aluminum, lanthanum, magnesium, simethicone, and sucralfate may bind to your thyroid hormone in your digestive tract, preventing your body from absorbing your medicine.

What might happen:

A decrease in the beneficial effects of your thyroid medicine may occur.

What you should do about this interaction:

Try to time your medicines so that you take your thyroid medicine at least 4 hours from may medicines that contain aluminum, magnesium, simethicone, or sucralfate or at least 2 hours from lanthanum. If you have any questions about how to schedule your medicines, ask your pharmacist.If you experience fatigue, sluggishness, constipation, stiffness, muscle cramps, loss of appetite, weight gain, dry skin, or difficulty in cold weather, contact your doctor.Your healthcare professionals (e.g. doctor or pharmacist) may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.

References:

1.Synthroid (levothyroxine sodium) US prescribing information. Abbott Laboratories June, 2011.
2.Fosrenol (lanthanum carbonate) US prescribing information. Shire US Inc. September, 2011.
3.Sherman SI, Tielens ET, Ladenson PW. Sucralfate causes malabsorption of L-thyroxine. Am J Med 1994 Jun;96(6):531-5.
4.Liel Y, Sperber AD, Shany S. Nonspecific intestinal adsorption of levothyroxine by aluminum hydroxide. Am J Med 1994 Oct;97(4):363-5.
5.Havrankova J, Lahaie R. Levothyroxine binding by sucralfate. Ann Intern Med 1992 Sep 1;117(5):445-6.
6.Vick K, Wennerberg P. Sucralfate-levothyroxine drug interaction..
7.Sperber AD, Liel Y. Evidence for interference with the intestinal absorption of levothyroxine sodium by aluminum hydroxide. Arch Intern Med 1992 Jan;152(1):183-4.
8.Mersebach H, Rasmussen AK, Kirkegaard L, Feldt-Rasmussen U. Intestinal adsorption of levothyroxine by antacids and laxatives: case stories and in vitro experiments. Pharmacol Toxicol 1999 Mar;84(3):107-9.

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