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Calcium with alendronate — GPhC CRA MCQ

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HardMusculoskeletal TherapeuticsCalcium with alendronateGPhC CRA

A patient stable on co-careldopa develops delayed “on” periods after starting a high-protein meal-replacement drink with each dose. Adherence and tablet formulation are unchanged. What is the most likely explanation?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: E — Dietary amino acids compete with levodopa and can impair its gastrointestinal absorption

Explanation lettering: E = shown as B · D = shown as C · B = shown as D · C = shown as E

A invents induction of a decarboxylase and incorrectly targets carbidopa. B is wrong because the clinically relevant effect is not urinary alkalinisation or rapid renal clearance. C is correct: certain dietary amino acids compete with levodopa and a high-protein diet can impair gastrointestinal absorption, producing delayed or reduced response. D invents irreversible binding to carbidopa. E is wrong because the interaction occurs after ingestion through nutrient competition, not chemical inactivation before swallowing.

Reference: Co-careldopa tablets SmPC. https://www.medicines.org.uk/emc/product/102157/smpc