What is the use and dosage of Amiodarone (Amiodarona) for treating irregular heartbeats?

Amiodarone Use and Dosing for Irregular Heartbeats

Amiodarone is primarily indicated for the treatment of life-threatening ventricular arrhythmias such as ventricular tachycardia and ventricular fibrillation, with a recommended loading dose of 150 mg IV over 10 minutes followed by 1 mg/min for 6 hours and 0.5 mg/min for 18 hours, with a maintenance dose of 200-600 mg daily. 1, 2

Indications

Amiodarone is indicated for:

• Ventricular fibrillation and hemodynamically unstable ventricular tachycardia refractory to other therapies 2
• Maintenance therapy for patients with symptomatic, sustained ventricular arrhythmias 1
• Second-line agent for rhythm control in atrial fibrillation, particularly in patients with structural heart disease 1

Dosing Protocol

IV Administration (Acute Setting)

• Loading dose: 150 mg IV over 10 minutes (may repeat in 10-30 minutes if necessary) 1
• Early maintenance: 1 mg/min for 6 hours (360 mg) 1
• Later maintenance: 0.5 mg/min for 18 hours (540 mg) 1
• Maximum dose: 2,100 mg/24 hours 1

Oral Administration

• Loading phase: 600 mg twice daily for 7 days 3
• Maintenance dose: 200-600 mg daily, with lowest effective dose preferred 4, 3

Administration Guidelines

• Use a volumetric infusion pump for IV administration 1
• Preferably administer through a central venous catheter 1
• Use an in-line filter 1
• Avoid concentrations >3 mg/mL due to risk of phlebitis 1
• IV infusions should generally be discontinued after 6-24 hours with reassessment 1

Monitoring Requirements

Baseline Testing

• Thyroid function tests (TSH, free T4, T3) 1
• Pulmonary function tests including DLCO 1
• Chest imaging (X-ray or high-resolution CT) 1
• Liver function tests 3
• ECG (for QT interval) 4

Ongoing Monitoring

• Thyroid function every 3-6 months 1
• Pulmonary function and chest imaging every 3-6 months 1
• Monitor for hypotension, bradycardia, and AV block (reported in 26% of cases) 1
• Regular ECG monitoring for QT prolongation 4

Efficacy

Amiodarone is highly effective for maintaining sinus rhythm, with a 65% success rate at 16 months compared to 37% for other agents 1. It is particularly valuable in patients with left ventricular dysfunction as it does not typically cause significant cardiodepression 5, 4.

Adverse Effects and Management

Common Side Effects

• Gastrointestinal: constipation, nausea (very common) 3
• Ocular: corneal microdeposits (almost universal) 3, 6
• Neurological: tremor, ataxia 3
• Dermatological: photosensitivity, hyperpigmentation 6

Serious Adverse Effects

• Pulmonary toxicity: subacute cough, progressive dyspnea, interstitial infiltrates 1
  • If suspected: discontinue amiodarone immediately and consider corticosteroids 1
• Thyroid dysfunction: both hyper- and hypothyroidism 1, 6
  • For hypothyroidism: continue amiodarone and add levothyroxine 1
  • For hyperthyroidism: consider antithyroid medications, prednisone, or amiodarone discontinuation 1

Drug Interactions

• Warfarin: increased anticoagulant effect 1
• Digoxin: increased serum levels 1
• Statins: risk of myopathy/rhabdomyolysis 1
• Beta-blockers and calcium channel blockers: potentiation of bradycardia 1

Important Caveats

• Despite its high efficacy, amiodarone should be considered a second-line agent due to its significant side effect profile 4
• Use the minimum effective dose to reduce risk of adverse effects 4
• Amiodarone has a very long half-life and unpredictable pharmacokinetics, requiring careful monitoring 4
• QT prolongation is common with amiodarone but rarely leads to torsades de pointes 4
• The drug is highly lipophilic with slow onset of action, necessitating loading doses 4

Amiodarone remains one of the most effective antiarrhythmic medications available, particularly for life-threatening ventricular arrhythmias, but requires vigilant monitoring and dose adjustment to balance efficacy with safety.