# A 70-year-old client newly prescribed verapamil sustained-release 240 mg orally daily for chronic stable angina is receiving discharge teaching. The client says, "I drink one large glass of grapefruit juice every morning with breakfast — that should be fine, right?" Which response by the nurse is most appropriate?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=374906&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A 70-year-old client newly prescribed verapamil sustained-release 240 mg orally daily for chronic stable angina is receiving discharge teaching. The client says, "I drink one large glass of grapefruit juice every morning with breakfast — that should be fine, right?" Which response by the nurse is most appropriate?

## Option

1. "Because grapefruit juice's effect on enzyme activity is temporary, taking verapamil at least 4 hours before the juice allows the drug to be absorbed without interaction; you can still enjoy your juice if you separate them."
2. "Grapefruit juice contains potassium, which can help lower blood pressure, and since verapamil also lowers blood pressure, having both is beneficial for your heart health; you should continue drinking it regularly."
3. "While grapefruit juice interacts with certain calcium channel blockers like felodipine, verapamil is metabolized differently, so there is no significant interaction; you may continue your usual morning juice without worry."
4. "Grapefruit juice inhibits the liver enzyme that breaks down verapamil, raising blood levels and increasing the risk of bradycardia, hypotension, and AV block; please avoid grapefruit and grapefruit juice while on this medication." **✔ Correct answer**

**Correct answer: 4**

## Explanation

Verapamil + grapefruit — CYP3A4 interaction
Grapefruit and grapefruit juice irreversibly inhibit intestinal CYP3A4, which metabolizes verapamil and many other drugs (e.g., other CCBs amlodipine·felodipine·nifedipine, statins, immunosuppressants, and some HIV drugs). Inhibition raises drug bioavailability and serum concentration, increasing verapamil-related bradycardia, AV block, hypotension, and heart failure exacerbation. The effect persists for up to 72 hours after a single glass — separating dose timing does not protect the patient. Standard teaching is to avoid grapefruit and grapefruit juice for the entire duration of therapy. Other notable verapamil interactions: digoxin (verapamil raises digoxin level), beta-blockers (additive bradycardia/AV block — usually contraindicated), and statins (rhabdomyolysis risk, dose-adjust simvastatin/lovastatin/atorvastatin).

## In-depth explanation

Clinical reasoning summary
Verapamil + grapefruit — CYP3A4 interaction
Grapefruit and grapefruit juice irreversibly inhibit intestinal CYP3A4, which metabolizes verapamil and many other drugs (e.g., other CCBs amlodipine·felodipine·nifedipine, statins, immunosuppressants, and some HIV drugs). Inhibition raises drug bioavailability and serum concentration, increasing verapamil-related bradycardia, AV block, hypotension, and heart failure exacerbation. The effect persists for up to 72 hours after a single glass — separating dose timing does not protect the patient. Standard teaching is to avoid grapefruit and grapefruit juice for the entire duration of therapy. Other notable verapamil interactions: digoxin (verapamil raises digoxin level), beta-blockers (additive bradycardia/AV block — usually contraindicated), and statins (rhabdomyolysis risk, dose-adjust simvastatin/lovastatin/atorvastatin).

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