QT-prolonging interaction — GPhC CRA MCQ
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Correct answer: B — Clarithromycin may increase QT prolongation risk with his psychotropic medicines
Clarithromycin can prolong QT interval and inhibit metabolism of several medicines. This patient already has prolonged QTc and is taking citalopram and quetiapine, both relevant to QT risk. The prescriber should review antibiotic choice and cardiac risk before supply. The concern is arrhythmia risk rather than reduced psychiatric medicine exposure.
Reference: BNF