How do I prescribe amiodarone for stable ventricular tachycardia?

Amiodarone Prescription for Stable Ventricular Tachycardia

For stable ventricular tachycardia, prescribe oral amiodarone at 800-1,600 mg/day in divided doses until a total of 10 g has been given, then reduce to a maintenance dose of 200-400 mg/day. 1

Initial Oral Loading Regimen

• Begin with oral amiodarone 800-1,600 mg/day divided into 2-3 doses to achieve therapeutic effect quickly 2, 1
• Continue this loading dose until a cumulative dose of 10 g has been administered (typically 1-2 weeks) 2, 1
• After the loading period, transition to a maintenance dose of 200-400 mg daily 2, 1
• The loading dose is essential as amiodarone has a long half-life and takes time to reach therapeutic levels 3

Intravenous Administration (If Needed)

• For patients unable to take oral medication or requiring more rapid effect, IV amiodarone can be administered 4
• IV dosing: 150 mg over 10 minutes (can be repeated in 10-30 minutes if necessary), followed by 1 mg/min for 6 hours, then 0.5 mg/min for 18 hours 2, 1
• Total IV dose over 24 hours should not exceed 2.2 g 1
• IV amiodarone should be administered via volumetric infusion pump, preferably through a central venous catheter 4

Transitioning from IV to Oral Therapy

• When transitioning from IV to oral therapy, dosing depends on duration of IV therapy 1:
  • IV therapy <1 week: 800-1,600 mg oral amiodarone daily 1
  • IV therapy 1-3 weeks: 600-800 mg oral amiodarone daily 1
  • IV therapy >3 weeks: 400 mg oral amiodarone daily 1

Monitoring Requirements

• Baseline assessment before initiating therapy:

  • ECG (QT interval, heart rate) 2
  • Liver function tests 2
  • Thyroid function tests 2
  • Pulmonary function tests and chest X-ray 2
  • Ophthalmologic examination 2

• During treatment:

  • ECG monitoring for QT prolongation and bradycardia 2, 1
  • Regular blood pressure monitoring for hypotension 1
  • Monitor for signs of pulmonary toxicity (cough, dyspnea) 1
  • Periodic liver and thyroid function tests 2

Clinical Considerations

• Amiodarone has a very long half-life (26-107 days), which affects dosing strategies and potential for drug interactions 5
• In patients with structural heart disease and life-threatening ventricular arrhythmias, consider implantable cardioverter-defibrillators (ICDs) as primary therapy, with amiodarone as an adjunct to reduce frequency of ICD shocks 2, 1
• Use the lowest effective maintenance dose possible to minimize risk of adverse effects 1
• Amiodarone is effective in 70-80% of patients with ventricular tachycardia refractory to other medications 6, 7

Potential Adverse Effects

• Common adverse effects include:

  • Bradycardia and QT prolongation 2, 1
  • Gastrointestinal upset and constipation 2, 1
  • Tremor or ataxia (dose-dependent) 6, 8
  • Visual disturbances 6

• Serious adverse effects to monitor for:

  • Pulmonary toxicity (most serious) - presents as subacute cough and progressive dyspnea 1
  • Thyroid dysfunction (both hypo- and hyperthyroidism) 6
  • Hepatotoxicity 4
  • Rarely, torsades de pointes 2

• Adverse effects correlate with total amiodarone exposure (dosage and duration), affecting approximately 50% of patients, but most can be managed with dose adjustments 6

Important Cautions

• Amiodarone has numerous drug interactions due to its effects on cytochrome P450 enzymes 2
• Avoid rapid IV administration as it can cause hypotension 1
• Concentrations >2 mg/mL for peripheral IV administration increase risk of phlebitis 4
• Neurologic toxicity is common at higher maintenance doses (600-800 mg/day) 8