IV Amiodarone Dosing and Management in Adults

Dosing Regimen

The ACC/AHA/HRS guidelines recommend a standard adult loading dose of 150 mg IV administered over 10 minutes, followed by an early maintenance infusion of 1 mg/min for 6 hours (≈360 mg) and a late maintenance infusion of 0.5 mg/min for the remaining 18 hours (≈540 mg), with a maximum 24‑hour total dose of 2.2 g. 1
For a 45‑kg patient, the 150 mg loading dose corresponds to ≈3.3 mg/kg, which is within the acceptable therapeutic range and does not require weight‑based adjustment. 1

Amiodarone must be diluted only in 5 % dextrose in water (D5W); use of normal saline or lactated Ringer’s can cause precipitation. 2
For the 150 mg loading dose, dilute in 100 mL of D5W to achieve a concentration ≤ 2 mg/mL for peripheral IV administration. Concentrations > 2 mg/mL require central venous access to prevent phlebitis. 1
An in‑line filter is recommended for all amiodarone infusions. 3

Continuous ECG monitoring is mandatory; bradycardia occurs in ~4.9 % of patients, and clinicians should watch for AV block, QT prolongation, and QRS changes. 1
Hypotension develops in ~16 % of patients and is directly related to infusion rate; blood pressure should be monitored continuously. 1
If the heart rate falls below 50 bpm with symptoms, the infusion should be reduced or stopped immediately. 3

Concomitant beta‑blockers, calcium‑channel blockers, or digoxin increase the risk of bradycardia. 3
When amiodarone is added to digoxin therapy, reduce the digoxin dose by ≈50 %. 4
When amiodarone is added to warfarin therapy, reduce the warfarin dose by 30–50 % and monitor INR weekly for 6 weeks. 1

The antiarrhythmic effect of IV amiodarone typically becomes apparent within 20–30 minutes of administration. 3
Conversion to sinus rhythm most commonly occurs after 6–8 hours and usually requires a cumulative dose of ≥1 g. 3

In cardiac arrest, the recommended dose is 5 mg/kg rapid bolus (≈225 mg for a 45‑kg patient), which may be repeated up to a total of 15 mg/kg per day. This rapid bolus is given after defibrillation and epinephrine have been initiated. 5

Do not give a rapid bolus in hemodynamically stable patients; rapid administration offers no therapeutic advantage and markedly increases hypotension risk. 2
For stable wide‑complex tachycardia or atrial fibrillation, infuse over 20–60 minutes rather than 10 minutes. 2
Prefer central venous access over peripheral administration when concentrations exceed 2 mg/mL to avoid phlebitis. 1
Do not discontinue abruptly in patients already on beta‑blockers or chronic amiodarone, to avoid rebound myocardial ischemia, infarction, and arrhythmias. 4

Hypotension: Slow or temporarily discontinue the infusion; hypotension is rate‑dependent and usually resolves with rate reduction. 1
Bradycardia: If heart rate < 50 bpm with symptoms, reduce the infusion rate by 50 % and consider holding other heart‑rate‑slowing drugs. Obtain an ECG to exclude heart block. 4
Heart block: Discontinue the infusion immediately; second‑ or third‑degree block is an absolute contraindication without pacemaker support. 1

For a 45‑kg adult, the standard adult dosing protocol is appropriate; no weight‑based adjustment is required. The loading dose of 150 mg (3.3 mg/kg) falls within the therapeutic range. 1
Maintenance infusion rates (1 mg/min then 0.5 mg/min) remain fixed and not weight‑adjusted for adults. However, patients with lower body weight should be monitored more closely for hypotension and bradycardia. 3
Amiodarone has a terminal elimination half‑life of 9–36 days (average ≈58 days), so effects persist long after discontinuation; specialist consultation is advised when considering use outside of cardiac arrest. 3