Calcium supplements can interfere with the absorption of which thyroid medication and which classes of antibiotics?

Prepare effectively for the Over-the-Counter Drugs, Herbal Supplements, Vitamins, and Minerals Test. Engage with detailed flashcards and interactive multiple-choice questions, accompanied by informative hints and explanations. Get exam-ready with confidence!

Calcium can bind certain drugs in the gut and form chelate complexes that aren’t absorbed well, so the drug’s effect can be diminished. Levothyroxine must be absorbed well to control thyroid hormone levels, and both tetracyclines and fluoroquinolones rely on good absorption too. When calcium supplements are taken together with these meds, the chelated drug stays in the gut and its blood levels drop, which can lessen their effectiveness.

To avoid this, space dosing apart by several hours. A common approach is to take levothyroxine on an empty stomach and separate calcium by about 4 hours; similarly, separate tetracyclines and fluoroquinolones from calcium by a few hours to maintain their absorption.

Other medications listed don’t have the same clinically significant calcium-chelation interaction, so calcium isn’t typically a concern with them in the same way.