Should metoprolol (beta blocker) and Entresto (sacubitril/valsartan) be withheld in a patient with a history of atrial fibrillation (A-fib) who is on a Cardizem (diltiazem) drip and has normotensive blood pressure?

Management of Medications During Cardizem Drip in a Patient with A-fib

Metoprolol and Entresto should be withheld while the patient is on a Cardizem (diltiazem) drip, especially when the patient is normotensive, due to the risk of bradycardia, heart block, and hypotension from combined negative chronotropic and hypotensive effects.

Rationale for Withholding Medications

Metoprolol (Beta-blocker)

• Concurrent use of intravenous diltiazem with beta-blockers is specifically contraindicated according to the FDA label 1
• The combination significantly increases the risk of:
  • Bradycardia
  • Heart block
  • Hypotension
  • Decreased cardiac contractility

Entresto (Sacubitril/Valsartan)

• Entresto has blood pressure-lowering effects that could compound the hypotensive effects of diltiazem
• In a normotensive patient on a Cardizem drip, adding Entresto increases the risk of symptomatic hypotension
• Guidelines recommend reconsidering the need for vasodilators when patients develop symptomatic hypotension 2

Evidence-Based Approach

1. Rate Control in Atrial Fibrillation

   • Diltiazem is a Class I, Level of Evidence B recommendation for acute rate control in A-fib 2
   • Both diltiazem and beta-blockers are effective for rate control, but should not be used together intravenously 2, 1

2. Drug Interactions

   • The FDA label for diltiazem explicitly states: "Intravenous diltiazem and intravenous beta-blockers should not be administered together or in close proximity (within a few hours)" 1
   • Studies have shown that the combination of diltiazem and beta-blockers can lead to significant conduction disturbances 3

3. Hemodynamic Considerations

   • Even in normotensive patients, the combination can lead to significant bradycardia and hypotension
   • The 2012 ESC guidelines specifically note that calcium channel blockers should be discontinued unless absolutely necessary when managing heart failure patients 2

Management Algorithm

1. During Cardizem Drip

   • Hold metoprolol completely
   • Hold Entresto while patient is on IV diltiazem
   • Monitor heart rate, blood pressure, and ECG closely
   • Watch for signs of bradycardia, heart block, or hypotension

2. Transitioning Off Cardizem Drip

   • Wait at least a few hours after discontinuing IV diltiazem before restarting metoprolol
   • Consider starting at a lower dose of metoprolol initially
   • Resume Entresto only after hemodynamic stability is confirmed
   • Monitor blood pressure closely during medication reinitiation

3. Special Considerations

   • If the patient has heart failure with reduced ejection fraction, be aware that diltiazem should be used cautiously due to negative inotropic effects 2, 4
   • Recent evidence suggests diltiazem may be associated with higher rates of adverse events compared to metoprolol in A-fib with RVR 5

Common Pitfalls to Avoid

• Abrupt discontinuation of beta-blockers: If the patient has been on long-term beta-blocker therapy, abrupt discontinuation can lead to rebound tachycardia and increased myocardial oxygen demand. However, during IV diltiazem therapy, the risks of combination therapy outweigh this concern 2

• Failure to monitor: Even if medications are withheld appropriately, continuous monitoring of heart rate, blood pressure, and cardiac rhythm is essential during Cardizem drip administration

• Premature reinitiation: Restarting metoprolol or Entresto too soon after discontinuing diltiazem infusion can still lead to adverse effects due to the lingering effects of diltiazem

By withholding both metoprolol and Entresto during Cardizem drip administration in this normotensive patient with A-fib, you can minimize the risk of serious adverse events while effectively managing the patient's atrial fibrillation.