How the interaction occurs:
If your cholesterol or phosphate binding medicine is taken at the same time as your thyroid medicine, it may also bind to the thyroid medicine in your digestive tract, preventing your body from absorbing the thyroid dose.
What might happen:
A decrease in the beneficial effects of your thyroid medicine may occur.
What you should do about this interaction:
Time your medicines so that you take your thyroid medicine four hours before or four hours after your cholesterol medicine or sevelamer.If you experience fatigue, sluggishness, constipation, stiffness, muscle cramps, loss of appetite, weight gain, dry skin, or difficulty in cold weather, contact your doctor. If you have questions about the timing of your medicines, ask your pharmacist.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.
1.Bergman F, Heedman PA, van der Linden W. Influence of cholestyramine on absorption and excretion of thyroxine in Syrian hamster. Acta Endocrinol (Copenh) 1966 Oct;53(2):256-63.
2.Northcutt RC, Stiel JN, Hollifield JW, Stant EG Jr. The influence of cholestyramine on thyroxine absorption. JAMA 1969 Jun 9;208(10):1857-61.
3.Harmon SM, Seifert CF. Levothyroxine-cholestyramine interaction reemphasized. Ann Intern Med 1991 Oct 15;115(8):658-9.
4.Lehrner LM, Weir MR. Acute ingestions of thyroid hormones. Pediatrics 1984 Mar;73(3):313-7.
5.Rosenberg R. Malabsorption of thyroid hormone with cholestyramine administration. Conn Med 1994 Feb;58(2):109.
6.Shakir KM, Michaels RD, Hays JH, Potter BB. The use of bile acid sequestrants to lower serum thyroid hormones in iatrogenic hyperthyroidism. Ann Intern Med 1993 Jan 15;118(2):112-3.
7.McLean M, Kirkwood I, Epstein M, Jones B, Hall C. Cation-exchange resin and inhibition of intestinal absorption of thyroxine. Lancet 1993 May 15; 341(8855):1286.
8.Welchol (colesevelam hydrochloride) US prescribing information. Daiichi Sankyo, Inc. June, 2013.
9.Brown KS, Armstrong IC, Wang A, Walker JR, Noveck RJ, Swearingen D, Allison M, Kissling JC, Kisicki J, Salazar DE. Effect of the bile acid sequestrant colesevelam on the pharmacokinetics of pioglitazone, repaglinide, estrogen estradiol, norethindrone, levothyroxine, and glyburide. J Clin Pharmacol 2010 May;50(5):554-65.
10.Renagel (sevelamer hydrochloride) US prescribing information. Genzyme Corporation June, 2011.
11.John-Kalarickal J, Pearlman G, Carlson HE. New medications which decrease levothyroxine absorption. Thyroid 2007 Aug;17(8):763-5.
12.Arnadottir M, Johannesson AJ. Phosphate binders and timing of levothyroxine administration. Nephrol Dial Transplant 2008 Jan;23(1):420.
13.Synthroid (levothyroxine sodium) US prescribing information. Abbott Laboratories June, 2011.