Possible Interaction: Thyroxine and Calcium Supplement

“Moreover, concomitant ingestion of calcium supplements , ferrous sulfate, proton-pump inhibitors, bile acid sequestrants, and sucralfate might influence LT4 absorption and/or metabolism.”

“Many foods and medications, including calcium supplements , can interfere with levothyroxine absorption.”

“DNA synthesis is significantly enhanced by preincubation at 37 degrees C in the presence of calcium , and the almost complete inhibition of DNA synthesis induced by extracts or bacterial polymerases in the presence of T4 ligase suggests that this chromatin activation involves calcium-dependent endonucleases.”

“ T4 level in serum was also increased by calcium.”

“Other factors reported by … could adversely affect levothyroxine absorption included use of prescription medications (20.6 %) and over-the-counter medications (34.… to treat comorbid gastrointestinal (GI) conditions; use of dietary supplements (51.8 %, primarily calcium and iron); and intake of foods/beverages … fiber, iodine, or soy (68.0 %).”

“Certain drugs, such as iron and calcium , reduce the gastrointestinal absorption of levothyroxine.”

“■ This supplement should be taken at least 2 hours apart from prescription medications as both fiber and calcium can affect absorption of certain medications, particularly tetracycline and floroquinolone antibiotics, levothyroxine , and digoxin.”

“Are you aware that clients taking levothyroxine (Levoxyl, Synthroid, Unithroid) should also be taking a calcium supplement and that the calcium supplement should be spaced at least 4 hours apart from levothyroxine?”

“When levothyroxine was coadministered with 2.0 g of calcium (as calcium carbonate), the maximum average T4 absorption decreased to 579 microg (57.9% of the dose ingested) at 240 minutes.”

“Hypothyroidism Ingestion of Thyroxine and Calcium Should Be Staggered Singh N, Singh PN, Hershman JM.”