What is the oral dose of amiodarone (antiarrhythmic medication) for a patient?

Oral Amiodarone Dosing

For most arrhythmias, start with an oral loading dose of 400-600 mg daily in divided doses for 2-4 weeks, then reduce to a maintenance dose of 100-200 mg daily. 1

Loading Dose Regimens by Indication

Ventricular Arrhythmias

• Begin with 800-1600 mg per day in divided doses until a cumulative total of 10 grams has been administered, then transition to maintenance therapy of 200-400 mg per day. 1, 2
• Higher loading doses (up to 1200 mg daily) may be used in monitored inpatient settings, though this increases adverse effect risk. 1
• The aggressive loading approach is necessary for life-threatening ventricular arrhythmias given the drug's prolonged time to therapeutic effect. 2

Atrial Fibrillation

• Use 600-800 mg per day in divided doses until a cumulative total of 10 grams has been given, then reduce to a maintenance dose of 200 mg per day. 1
• This lower loading dose compared to ventricular arrhythmias reflects the generally less urgent nature of atrial fibrillation control. 1

Supraventricular Tachycardia

• Arrhythmias may be controlled with smaller maintenance doses of 100-400 mg/day without aggressive loading in many cases. 3

Transitioning from IV to Oral Therapy

The oral dose depends critically on the duration of prior IV therapy, as patients accumulate significant tissue stores during IV administration: 1, 2

• IV therapy <1 week: Start 800-1600 mg oral daily 1, 2
• IV therapy 1-3 weeks: Start 600-800 mg oral daily 1, 2
• IV therapy >3 weeks: Start 400 mg oral daily 1, 2

This duration-based approach prevents excessive drug accumulation, as patients on prolonged IV therapy have already loaded significant tissue stores. 1

Maintenance Dosing Strategy

After completing the loading phase, reduce to 200-400 mg daily, or even lower (100-200 mg daily) if tolerated, as virtually all patients develop side effects at higher maintenance doses. 1

• The dose should be kept at the lowest effective level to minimize toxicity. 4
• For supraventricular arrhythmias specifically, maintenance doses of 100-400 mg/day are typically sufficient. 3
• Doses should be reduced if side effects occur during the loading or maintenance phase. 1

Critical Pharmacokinetic Considerations

Amiodarone has an extremely long half-life averaging 58 days (range 15-100 days), meaning full antiarrhythmic effects may take days to weeks despite adequate serum levels. 1, 4

• Maximal therapeutic and adverse effects are not attained before 90-150 days of treatment. 3
• Antiarrhythmic protection may persist for up to 150 days or more after discontinuation. 3
• This prolonged pharmacokinetic profile explains why aggressive loading is often necessary for urgent arrhythmia control. 1

Essential Monitoring During Loading and Maintenance

Watch continuously for bradycardia, QT prolongation, hypotension, and heart block during the loading phase. 1

• Monitor liver and thyroid function every 6 months during maintenance therapy. 4
• Screen for pulmonary toxicity with baseline and periodic pulmonary function assessment, as this represents the most serious potential adverse effect. 2
• Frequency of adverse effects correlates directly with total amiodarone exposure (dosage and duration). 2

Critical Drug Interactions Requiring Dose Adjustment

Reduce digoxin dose by 50% when starting amiodarone, as digoxin levels predictably double. 4

Reduce warfarin dose by one-third to one-half and monitor INR at least weekly for the first 6 weeks, as interaction effects don't peak until 7 weeks. 4

• Avoid coadministration with other QT-prolonging medications without expert consultation. 1
• Patients must not consume grapefruit or grapefruit juice, as it inhibits metabolism and increases plasma levels. 4

Common Pitfalls to Avoid

• Do not use standard maintenance doses (600 mg daily) long-term, as 93% of patients develop side effects at this dose level. 5
• Do not expect immediate therapeutic effect—the pretherapeutic latency period varies by arrhythmia type and dose employed. 3
• Do not discontinue abruptly for perceived lack of effect—tissue loading takes weeks to months. 1
• The first sign of antiarrhythmic failure may manifest as sudden cardiac death, emphasizing the need for careful patient selection and monitoring. 5