What is the recommended amiodarone dosing regimen for a hemodynamically stable patient with a wide‑complex tachycardia who has a palpable pulse?

Amiodarone Dosing for Wide Complex Tachycardia with Pulse

For hemodynamically stable wide complex tachycardia, administer amiodarone 150 mg IV over 10 minutes, followed by a maintenance infusion of 1 mg/min for 6 hours, then 0.5 mg/min for the remaining 18 hours, with a maximum total dose of 2.2 g over 24 hours. 1

Initial Loading Dose

• Administer 150 mg IV over 10 minutes as the initial bolus for hemodynamically stable monomorphic ventricular tachycardia 1
• This loading dose can be repeated if breakthrough episodes of ventricular tachycardia or ventricular fibrillation occur 2
• The 150 mg bolus should be diluted in 100 mL of 5% dextrose (D5W) 1, 3

Maintenance Infusion Protocol

• Early maintenance: 1 mg/min for 6 hours (total 360 mg) following the initial bolus 1, 4
• Late maintenance: 0.5 mg/min for 18 hours (total 540 mg) to complete the 24-hour regimen 1, 4
• The total dose delivered over the first 24 hours is approximately 1000 mg (150 mg bolus + 360 mg + 540 mg) 1, 2
• Maximum cumulative dose: 2.2 g over 24 hours should not be exceeded 1, 4

Important Clinical Considerations

Onset of Action

• Expect the antiarrhythmic effect to develop 20-30 minutes after IV administration, which reflects the relatively slow onset of amiodarone's class III effects 5
• Most conversions to sinus rhythm occur after 6-8 hours of therapy, often requiring ≥1000 mg total dose 4, 6
• The delayed onset makes amiodarone less suitable as a first-line agent unless the patient is clinically stable 1

Administration Route and Concentration

• Use a central venous catheter whenever possible, as peripheral administration with concentrations >2 mg/mL frequently causes phlebitis 3
• Amiodarone must be diluted only in 5% dextrose (D5W); normal saline or lactated Ringer's solution will cause precipitation 3
• An in-line filter should be used during administration 3

Hemodynamic Monitoring Requirements

Continuous monitoring is mandatory for the following parameters 4, 3:

• Heart rate and rhythm
• Blood pressure (hypotension occurs in 16-26% of patients) 1, 7
• AV conduction abnormalities and heart block (bradycardia occurs in 4.9% of patients) 1, 3
• QT interval, PR interval, and QRS duration 4, 3

Relative Contraindications and Cautions

Amiodarone should be used with extreme caution in patients with 3:

• Baseline heart rate <60 beats/min (relative contraindication unless immediately life-threatening) 3
• Systolic blood pressure <100 mm Hg (increased risk of hemodynamic compromise) 3
• Moderate or severe left ventricular dysfunction (may exacerbate hypotension) 3

Absolute contraindications include 2:

• Second- or third-degree AV block without a functioning pacemaker 2
• Cardiogenic shock 2
• Marked sinus bradycardia 2

Management of Adverse Effects

• If hypotension develops: Slow the infusion rate, consider vasopressor drugs, positive inotropic agents, or volume expansion 2
• If bradycardia or heart block occurs: Slow the infusion or discontinue immediately 2
• If the heart rate decreases by 10 beats per minute during infusion, reduce the infusion rate 3

Alternative Agents and Clinical Context

When to Consider Other Options

• Procainamide is an alternative for hemodynamically stable monomorphic VT, dosed at 20-50 mg/min until arrhythmia suppression, hypotension, QRS prolongation by 50%, or maximum cumulative dose of 17 mg/kg 1
• Lidocaine may be considered if amiodarone is not available, with an initial dose of 1-1.5 mg/kg IV 1
• Electrical cardioversion should be prioritized if the patient becomes hemodynamically unstable at any point 1

Efficacy Considerations

• Research demonstrates that IV amiodarone has only a 29% success rate for acute termination of sustained monomorphic VT within 20 minutes, reflecting its slow onset of action 8
• However, amiodarone remains valuable in patients with structural heart disease or left ventricular dysfunction, where class IC drugs are contraindicated 4, 6
• The dose-response relationship shows improved efficacy with higher doses, with event rates decreasing significantly from 125 mg to 1000 mg regimens 7

Common Pitfalls to Avoid

• Do not use normal saline as a diluent—this causes drug precipitation and loss of efficacy 3
• Do not exceed 2 mg/mL concentration in peripheral veins due to high phlebitis risk 3
• Do not expect immediate rhythm conversion—continue monitoring for at least 20-30 minutes to allow drug effect 5, 8
• Reduce digoxin dose by 50% if the patient is on concurrent digoxin therapy, as amiodarone doubles digoxin levels 3
• Monitor INR weekly if the patient is on warfarin, as amiodarone significantly increases anticoagulation effects 3