A nurse is reinforcing discharge teaching with a client prescribed verapamil to treat angina. Which of the following instructions should the nurse include?

A. Monitor for decreased heart rate while taking this medication: Verapamil (a nondihydropyridine calcium channel blocker) lowers heart rate (can cause bradycardia). Patients should monitor for decreased heart rate, dizziness, or syncope and report symptoms. B. Consume a low-residue diet while taking this medication: Verapamil commonly causes constipation; a low-residue diet would likely worsen constipation. Instead encourage adequate dietary fiber and fluids (unless contraindicated) and report severe constipation. C. Take the medication as needed at the onset of chest pain: Verapamil is usually given on a scheduled basis for chronic angina/arrhythmia management—not as an immediate PRN rescue for acute chest pain. Short-acting nitroglycerin is used for acute chest pain. D. Take the medication with citrus juice: Grapefruit juice (a citrus product) can increase blood levels of verapamil by inhibiting CYP3A4, raising the risk of adverse effects. Patients should avoid grapefruit/grapefruit juice while on verapamil.