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

Choice A rationale Verapamil is a calcium channel blocker used for the long-term management and prophylaxis of chronic stable angina or hypertension. It is not intended for the immediate relief of acute anginal attacks. Acute chest pain should be treated with fast-acting vasodilators like sublingual nitroglycerin. Instructing a client to take verapamil on an as-needed basis for chest pain is incorrect and dangerous, as the medication requires consistent dosing to maintain therapeutic blood levels and prevent coronary vasospasm. Choice B rationale Verapamil frequently causes constipation by slowing the movement of the gastrointestinal tract due to its inhibitory effect on smooth muscle calcium channels. Increasing dietary fiber and fluid intake is necessary to manage this side effect. However, if a client is instructed on a low-residue diet, they would actually be at higher risk for severe constipation. While the instruction here focuses on fiber management, the scientific rationale is that calcium channel blockers significantly impact bowel motility, requiring specific dietary adjustments to maintain regularity. Choice C rationale Taking verapamil with certain fruit juices, particularly grapefruit juice, can be dangerous. Grapefruit juice inhibits the CYP3A4 enzyme in the intestinal wall, which is responsible for the metabolism of many calcium channel blockers. This inhibition can lead to significantly increased serum levels of verapamil, resulting in toxicity characterized by severe bradycardia, hypotension, and heart block. Most other citrus juices are safe, but the lack of specificity in "citrus juice" usually prompts caution to avoid potential enzyme interactions. Choice D rationale Verapamil is a non-dihydropyridine calcium channel blocker that has significant negative inotropic and chronotropic effects. It works by blocking calcium entry into the sinoatrial and atrioventricular nodes, which decreases the heart rate and slows conduction. Therefore, clients should be monitored for bradycardia, not an increased heart rate. An elevated heart rate while taking verapamil would be an unexpected finding and might indicate a different underlying issue or a lack of therapeutic efficacy of the medication.