Medications that interfere with thyroid hormone absorption

These are medications that reduce the absorption of thyroid hormone in the gastrointestinal system significantly. These medications/foods lead to erratic thyroid hormone levels in the blood. Generally they should not be taken within four hours of taking thyroid medication. It is strongly advised that you speak to your physician before changing medication frequency or dosages. 


–Colestipol hydrochloride 
–Sucralfate 
–Ferrous sulfate 
–Calcium Carbonate tablets (milk and dairy and almond milk are fine)
–Foods (soybean formula, walnuts, prunes) 
–Aluminum hydroxide 
–Cholestyramine 
–Sodium polystyrene sulfonate 
–Laxatives 
–Orlistat (Alli)
- Vitamin D3
- Proton pump inhibitors for heart burn


2014 study 
The tablet formulation of levothyroxine requires gastric pH in order to dissolve and be appropriately absorbed by the intestine. Interference from other treatments such as proton-pump inhibitors, however, may prevent proper absorption. in 2014 new levothyroxine formulations have been developed, some of which are now available in some countries. One such new formulation is a liquid oral solution that does not require dissolution for absorption.  To determine whether the liquid oral solution prevents the malabsorption caused by proton-pump inhibitors, researchers evaluated outcomes in patients before or after switching from the tablet to liquid formulation.  24 patients whose tablet LT4 absorption was impaired due to concomitant ingestion of PPI. To gauge LT4 absorption, researchers measured thyroid-stimulating hormone (TSH) values at baseline (before switching to liquid LT4), 8 weeks after the formulation change and again after another 8 weeks.  After switching, overall serum TSH levels were significantly lower post-switch compared with pre-switch levels. In 7.1% of the patients, LT4 absorption increased so much that their doses had to be lowered to prevent hyperthyroidism.


Updated 12-21-2014
References
Endocr Pract. 2014 Jul;20(7):657-62. doi: 10.4158/EP13418.OR. Comparison of TSH Levels with Liquid Formulation Versus Tablet Formulations of Levothyroxine in the Treatment of Adult Hypothyroidism. Brancato D1, Scorsone A1, Saura G1, Ferrara L1, Di Noto A1, Aiello V1, Fleres M1, Provenzano V1.
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