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Antacid interaction — GPhC CRA MCQ

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ModerateGastro-intestinal TherapeuticsAntacid interactionGPhC CRA

A patient taking doxycycline asks to buy an indigestion remedy containing magnesium and aluminium salts. He plans to take it with his antibiotic dose. What is the most important interaction to flag?

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Correct answer: E — Antacids can reduce doxycycline absorption

Multivalent cations in antacids can chelate tetracyclines and reduce absorption. Doxycycline and antacids should be separated according to product advice. Reduced antibiotic exposure can risk treatment failure.

Reference: BNF