Levothyroxine Colestyramine

The absorption of some drugs may also be reduced if they are given with adsorbents such as charcoal or kaolin, or anionic exchange resins such as colestyramine or colestipol. The absorption of propranolol, digoxin, warfarin, tricyclic antidepressants, ciclosporin and levothyroxine is reduced by colestyramine. 

The absorption of thyroid extract, levothyroxine, and tri-iodothy-ronine from the gut is reduced by the concurrent use of colestyramine. 

A patient with hypothyroidism, taking levothyroxine, had a fall in his basal metabolic rate when given colestyramine this prompted a further study in two similar patients taking thyroid extract 60 mg daily or levothyroxine sodium 100 micrograms daily, and 5 healthy subjeets. Colestyramine... 

Another report deseribes a patient taking levothyroxine whose TSH levels rose when colestyramine was taken, and fell again when it was stopped, indicating an impairment of levothyroxine absorption. ... 

Colestyramine binds to levothyroxine in the gut, thereby reducing its absorption. Since levothyroxine probably also undergoes enterohepatic recirculation, continued contact with the colestyramine is possible and separating administration may not entirely eliminate the interaction. 

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