Should the scheduled digoxin dose be held for now given the patient's stable heart rate and ongoing amiodarone drip?

Management of Atrial Fibrillation with RVR: Hold Digoxin When on Amiodarone Drip

Yes, the scheduled digoxin 1mL IV dose should be held for now given the patient's stable heart rate of 65 bpm and ongoing amiodarone drip. 1

Rationale for Holding Digoxin

• The patient currently has:
  • Heart rate of 65 bpm (already well-controlled)
  • Blood pressure of 111/56 mmHg with MAP 81
  • Ongoing amiodarone drip at 33.3 mL/hr (scheduled to decrease to 16.7 mL/hr at 2300)

Drug Interaction Concerns

1. Amiodarone-Digoxin Interaction: Amiodarone significantly increases serum digoxin concentrations by:

   • Inhibiting P-glycoprotein 1
   • Reducing digoxin clearance
   • Causing tissue-to-plasma redistribution of digoxin 2

2. Risk of Bradycardia:

   • The patient's heart rate is already 65 bpm
   • Combined negative chronotropic effects of both drugs could lead to symptomatic bradycardia 1
   • Amiodarone alone can cause bradycardia, and this risk is amplified when combined with digoxin 1

Guidelines for Rate Control in AF

According to ACC/AHA/ESC guidelines for atrial fibrillation management:

1. Amiodarone is effective for rate control when other measures are unsuccessful or contraindicated (Class IIa, LOE C) 1

2. Digoxin dosing considerations:

   • When used with amiodarone, digoxin dose should be reduced due to drug interactions 1
   • Digoxin toxicity can occur at lower serum levels when used with amiodarone 1

3. Heart rate target:

   • Current heart rate of 65 bpm is already within target range
   • No additional rate control agent is needed at this time

Management Algorithm

1. Current situation (HR 65, stable BP, on amiodarone drip):

   • Hold the scheduled digoxin dose
   • Continue amiodarone drip as planned with titration to 16.7 mL/hr at 2300
   • Monitor vital signs closely

2. If heart rate increases above 100 bpm:

   • Reassess the need for rate control
   • Consider administering digoxin at a reduced dose (50% of normal dose) 1

3. If bradycardia develops (HR < 50 bpm):

   • Consider further reducing or temporarily stopping the amiodarone infusion
   • Monitor for signs of hemodynamic compromise

Important Considerations

• Monitoring: Continue close cardiac monitoring while on amiodarone infusion 1
• Digoxin levels: If digoxin is restarted, be aware that levels may fluctuate significantly when measured at different times in relation to amiodarone administration 2
• Dose adjustment: If both medications are needed long-term, the digoxin maintenance dose should be reduced by 30-50% when used with amiodarone 1

Common Pitfalls to Avoid

1. Measuring digoxin levels too soon after amiodarone: Levels may not accurately reflect tissue concentrations due to redistribution 2

2. Failure to recognize digoxin toxicity: Symptoms may occur at lower serum levels when combined with amiodarone 1

3. Overlooking the additive effects on AV nodal conduction: Both drugs slow AV conduction and can cause excessive bradycardia when combined 1

The most prudent approach is to hold the digoxin dose while the patient's heart rate is adequately controlled on amiodarone, preventing potential adverse effects from this significant drug interaction.