What is the loading dose of amiodarone?

Amiodarone Loading Dose

For acute ventricular arrhythmias (VF/VT), administer 150 mg IV over 10 minutes, which can be repeated as needed if VT recurs, followed by a maintenance infusion of 1 mg/min for 6 hours, then 0.5 mg/min, with a maximum total dose of 2.2 g IV per 24 hours. 1, 2

Intravenous Loading Regimen for Acute Arrhythmias

The FDA-approved IV loading protocol delivers approximately 1000 mg over the first 24 hours using a three-stage approach 2:

• Rapid loading infusion: 150 mg over 10 minutes 1
• Early maintenance infusion: 1 mg/min for 6 hours (360 mg) 1, 2
• Late maintenance infusion: 0.5 mg/min for 18 hours (540 mg) 2

For breakthrough VF or hemodynamically unstable VT, give supplemental 150 mg boluses over 10 minutes as needed. 1, 2 The initial infusion rate should not exceed 30 mg/min to minimize hypotension risk 2.

Critical Administration Details

• Use concentrations ≤2 mg/mL for peripheral IV access to reduce phlebitis risk; concentrations >2 mg/mL require central venous access 2
• Administer through a volumetric infusion pump (not drop counters, which can underdose by up to 30%) 2
• Use an in-line filter and glass or polyolefin bottles for infusions >1 hour 2
• Higher doses (300 mg bolus) increase hypotension frequency, though newer formulations without vasoactive solvents may reduce this risk 1

Oral Loading Regimen for Non-Acute Settings

For maintenance of sinus rhythm or chronic arrhythmia suppression, oral loading follows a different approach:

Standard Oral Loading Options

Two primary loading strategies are recommended 1:

• 600 mg daily for 4 weeks (total 16.8 g), then reduce to maintenance 1
• 1000 mg daily for 1 week (total 7 g), then reduce to maintenance 1

Alternative intensive loading: 400-600 mg daily in divided doses for 2-4 weeks, followed by 100-200 mg daily maintenance 1

Transition from IV to Oral Therapy

When transitioning from IV to oral amiodarone after hospitalization for VT 3:

• If IV therapy <1 week: Start 800-1,600 mg oral daily in divided doses 3
• If IV therapy 1-3 weeks: Start 600-800 mg oral daily 3
• If IV therapy >3 weeks: Start 400 mg oral daily 3

Continue loading until cumulative dose of 10 g is achieved, then reduce to maintenance of 200-400 mg daily 1, 3

Context-Specific Dosing Considerations

For Atrial Fibrillation Cardioversion

Inpatient loading: 1.2-1.8 g per day in divided doses until 10 g total, then 200-400 mg daily maintenance 1

Single-dose approach: 30 mg/kg as a single oral dose has been studied for cardioversion 1

For Refractory Ventricular Arrhythmias

Higher loading doses (up to 1200 mg/day) may be considered in monitored inpatient settings, though doses >2100 mg/24 hours are associated with increased hypotension risk 1, 2

Critical Safety Considerations

Hypotension Risk

Treatment-emergent hypotension occurs in approximately 16% of patients receiving IV amiodarone, with no correlation to baseline ejection fraction 2. The risk increases with:

• Rapid infusion rates >30 mg/min 2
• Total doses >2100 mg/24 hours 2
• Concentrations >3 mg/mL causing peripheral vein phlebitis 2

Monitoring During Loading

During IV loading, monitor continuously for 1:

• Hypotension requiring fluid resuscitation or vasopressors
• Bradycardia or heart block
• QT prolongation (though torsades is rare) 1

During oral loading, assess weekly for 1:

• PR interval prolongation
• QRS duration (should not exceed 150% of baseline)
• QT interval changes
• Heart rate (reduce other rate-control medications as needed)

Drug Interactions During Loading

Reduce doses of concomitant medications immediately 1, 3:

• Warfarin: Decrease by 50% 1, 3
• Digoxin: Decrease by 30-50% 1, 3
• Monitor levels of beta-blockers, calcium channel blockers, and statins 3

Common Pitfalls to Avoid

Do not use drop-counter infusion sets for IV administration, as surface tension changes can cause 30% underdosing 2

Do not exceed 2 mg/mL concentration without central access, as peripheral phlebitis risk is unacceptably high 2

Do not start multiple antiarrhythmic drugs simultaneously with amiodarone, as proarrhythmic risk increases substantially 1

Do not assume immediate effect—IV amiodarone shows rapid onset (within hours) 2, but oral loading requires 90-150 days for maximal antiarrhythmic effect due to the 30-day elimination half-life 4, 5, 6