What is the recommended administration protocol for amiodarone (antiarrhythmic medication)?

How to Administer Amiodarone

For IV amiodarone, administer 150 mg over 10 minutes as a loading dose, followed by 1 mg/min for 6 hours, then 0.5 mg/min for maintenance, using a central venous catheter whenever possible with concentrations >2 mg/mL, and always use a volumetric infusion pump with an in-line filter. 1, 2

Intravenous Administration Protocol

Initial Loading Regimen (First 24 Hours)

• Rapid loading: 150 mg over 10 minutes 1, 2
• Early maintenance: 1 mg/min for 6 hours 1, 2
• Late maintenance: 0.5 mg/min for 18 hours 1, 2
• Total first 24-hour dose: Approximately 1000 mg 2
• Do not exceed an initial infusion rate of 30 mg/min 2

Supplemental Dosing for Breakthrough Arrhythmias

• For breakthrough ventricular fibrillation or hemodynamically unstable ventricular tachycardia: 150 mg supplemental infusion mixed in 100 mL D5W over 10 minutes 2
• Mean daily doses above 2100 mg are associated with increased risk of hypotension 2

Ongoing Maintenance Infusion

• Continue 0.5 mg/min (720 mg per 24 hours) after the first 24 hours 2
• Maintenance infusion can be continued for 2-3 weeks regardless of age, renal function, or left ventricular function 2
• The infusion rate may be increased to achieve effective arrhythmia suppression 2

Critical Administration Requirements

Vascular Access and Equipment

• Use a central venous catheter whenever possible, especially for concentrations >2 mg/mL 3, 2
• Peripheral vein phlebitis occurs frequently with concentrations >2 mg/mL 2
• For infusions >1 hour, do not exceed 2 mg/mL concentration unless using a central line 2
• Must use a volumetric infusion pump (drop counter sets can underdose by up to 30%) 2
• Use an in-line filter during administration 2

Solution Preparation

• Administer in glass or polyolefin bottles containing D5W for infusions exceeding 2 hours 2
• Do not use evacuated glass containers for admixing (may cause precipitation) 2
• Acceptable concentration range: 1-6 mg/mL (use central line for >2 mg/mL) 2
• Does not require protection from light during administration 2

Oral Administration Protocol

Loading Regimens

Two acceptable loading approaches exist:

• Standard loading: 600 mg daily for 4 weeks 1
• Rapid loading: 1000 mg daily for 1 week 1
• Alternative loading: 600-800 mg daily in divided doses to a total load of up to 10 g 1

Maintenance Dosing

• Target maintenance dose: 200 mg daily after loading 1
• Keep dosage at the lowest effective level to minimize toxicity 3
• The dose should be titrated based on clinical response 1

Monitoring During Administration

Continuous Monitoring Requirements

• Continuous ECG monitoring is mandatory for heart rate, AV conduction abnormalities, and QT prolongation 3
• Monitor for bradycardia (occurs in 4.9% of IV patients) 3
• Monitor for hypotension (occurs in 16% of IV patients) 3
• Watch for second- or third-degree heart block (absolute contraindication without pacemaker) 3

Heart Rate Management

• If heart rate decreases by 10 beats per minute, reduce the infusion rate 3
• If bradycardia or heart block develops, discontinue or reduce infusion rate immediately 3

Critical Drug Interactions Requiring Dose Adjustments

Warfarin

• Reduce warfarin dose by one-third to one-half when starting amiodarone 3, 2
• Monitor INR at least weekly for the first 6 weeks 3
• Interaction effects don't peak until 7 weeks 3

Digoxin

• Reduce digoxin dose by approximately 50% when starting amiodarone 3
• Digoxin levels typically double with amiodarone co-administration 3

Other Rate-Controlling Agents

• Concomitant beta-blockers, calcium channel blockers, or digoxin create additive effects and increase bradycardia risk 3
• Reduce doses of other rate control medications when rate slows after amiodarone initiation 1

Contraindications and Precautions

Absolute Contraindications

• Second- or third-degree heart block without a pacemaker 3, 4
• Severe bradycardia without pacemaker support 3

Use with Extreme Caution

• Heart rate <60 bpm (relatively contraindicated unless pacemaker present or immediately life-threatening situation) 3
• Systolic blood pressure <100 mmHg 1
• Moderate or severe left ventricular failure 1

Transition from IV to Oral Therapy

Switching Protocol

The optimal dose depends on the duration of IV therapy and bioavailability of oral formulation 2. Due to amiodarone's extremely long half-life (average 58 days, range 15-100 days), there is significant overlap between IV and oral dosing 3.

Important Dietary Restriction

• Patients must not consume grapefruit or grapefruit juice during amiodarone therapy, as it inhibits CYP3A-mediated metabolism and increases plasma levels 3, 2

Common Pitfalls to Avoid

• Never use drop counter infusion sets (can underdose by 30%) 2
• Never exceed 2 mg/mL concentration for peripheral IV access 2
• Never use evacuated glass containers for mixing 2
• Do not start amiodarone without first checking baseline QT interval, electrolytes, and thyroid function 1
• Faster infusion rates than recommended have resulted in hepatocellular necrosis, acute renal failure, and death 2