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Levothyroxine and calcium — GPhC CRA MCQ

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EasyDrug InteractionsLevothyroxine and calciumGPhC CRA

A 67-year-old woman takes levothyroxine every morning. She is newly prescribed calcium carbonate with colecalciferol and plans to take both together before breakfast. What is the most important interaction to flag?

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Correct answer: B — Calcium carbonate can reduce levothyroxine absorption

Calcium salts can bind levothyroxine and reduce its absorption. The doses should be separated by several hours and levothyroxine taken consistently. Thyroid function should be monitored after changes that may affect absorption.

Reference: BNF