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levothyroxine oral

Anticoagulants/Thyroid

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:

Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

When these two medicines are taken together, thyroid may decrease the amount of blood-thinner that your body needs.

What might happen:

The effect of the blood-thinner may increase. You may experience an increased chance for bleeding, including bleeding from your gums, nosebleeds, unusual bruising, or dark stools. If you stop taking your thyroid, you could have an increased risk of clots.

What you should do about this interaction:

Ask your healthcare professionals (e.g. doctor or pharmacist) about taking these medicines together. If your doctor prescribes these medicines together, you may need to have your bleeding times checked more often. If you have any signs of bleeding, such as bleeding from your gums, nosebleeds, unusual bruising, or dark stools, contact your doctor right away.Your healthcare professionals 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.Walters MB. The relationship between thyroid function and anticoagulant therapy. Am J Cardiol 1963 Jan;11:112-4.
2.Schrogie JJ, Solomon HM. The anticoagulant response to bishydroxycoumarin. II. The effect of D- thyroxine, clofibrate, and norethandrolone. Clin Pharmacol Ther 1967 Jan-Feb;8(1):70-7.
3.Kimberg DV. The liver. In: Werner SC, Ingbar SH, ed. Werner and Ingbar's The thyroid. New York: Harper & Row; 1971: 569..
4.Feely J, Stevenson IH, Crooks J. Altered plasma protein binding of drugs in thyroid disease. Clin Pharmacokinet 1981 Jul-Aug;6(4):298-305.
5.Weintraub M, Breckenridge RT, Griner PF. The effects of dextrothyroxine on the kinetics of prothrombin activity: proposed mechanism of the potentiation of warfarin by D-thyroxine. J Lab Clin Med 1973 Feb; 81(2):273-9.
6.Owens JC, Neely WB, Owen WR. Effect of sodium dextrothyroxine in patients receiving anticoagulants. N Engl J Med 1962 Jan 11;266(2):76-9.
7.Self T, Weisburst M, Wooten E, Straughn A, Oliver J. Warfarin-induced hypoprothrombinemia. Potentiation by hyperthyroidism. JAMA 1975 Mar 17; 231(11):1165-6.
8.Rice AJ, McIntosh TJ, Fouts JR, Brunk SF, Wilson WR. Decreased sensitivity to warfarin in patients with myxedema. Am J Med Sci 1971 Oct;262(4):211-5.
9.Vagenakis AG, Cote R, Miller ME, Braverman LE, Stohlman F Jr. Enhancement of warfarin-induced hypoprothrombinemia by thyrotoxicosis. Johns Hopkins Med J 1972 Jul;131(1):69-73.
10.Gotta AW, Sullivan CA, Seaman J, Jean-Gilles B. Prolonged intraoperative bleeding caused by propylthiouracil-induced hypoprothrombinemia. Anesthesiology 1972 Nov;37(5):562-3.
11.Costigan DC, Freedman MH, Ehrlich RM. Potentiation of oral anticoagulant effect by L-thyroxine. Clin Pediatr (Phila) 1984 Mar;23(3):172-4.

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