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QT prolongation interaction — GPhC CRA MCQ

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HardDrug InteractionsQT prolongation interactionGPhC CRA

A 46-year-old man taking methadone 80 mg daily is prescribed citalopram 20 mg daily. His record shows previous prolonged QT interval and he also takes quetiapine at night. What is the most important interaction to flag?

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Correct answer: C — Additive QT prolongation with methadone and citalopram

Methadone and citalopram both carry QT-prolongation risk, and quetiapine plus previous QT prolongation increases concern. This requires prescriber review and consideration of ECG and alternative therapy. The pharmacist should also assess for syncope or palpitations.

Reference: BNF