What is the typical dosing regimen for amiodarone in the treatment of arrhythmias?

Amiodarone Dosing Regimen for Arrhythmias

The recommended amiodarone dosing regimen consists of a loading dose of 600-800 mg daily for 7 days (total 4.2-5.6g), followed by a maintenance dose of 200-400 mg daily, with 200 mg daily often being effective with fewer side effects. 1

Loading Dose Protocol

• Oral Loading:

  • 600-800 mg daily in divided doses until reaching a total of 10g 1
  • Alternative high-dose loading (for unstable patients): 50 mg/kg/day for 3 days, then 30 mg/kg/day for 2 days 2

• IV to Oral Conversion: Adjust oral loading dose based on duration of previous IV therapy 1:

  • <1 week of IV therapy: 800-1600 mg daily
  • 1-3 weeks of IV therapy: 600-800 mg daily

  • 3 weeks of IV therapy: 400 mg daily

• Initial IV Administration: 5-7 mg/kg over 30-60 minutes, followed by 1.2-1.8 g/day continuous IV or divided oral doses until 10g total 1

Maintenance Dose

• Standard maintenance: 200-400 mg daily 1
• Lower dose (200 mg daily) often provides effective rhythm control with fewer side effects 1
• Dose adjustments should be made based on:
  • Clinical response
  • Side effect profile
  • Age
  • Renal function
  • Hepatic function

Monitoring Requirements

• During loading phase: Monitor for:

  • QT interval prolongation
  • Bradycardia
  • Gastrointestinal side effects
  • Neurological effects

• Long-term monitoring (every 6 months):

  • Thyroid function tests
  • Liver function tests
  • ECG monitoring for QT prolongation and bradycardia
  • Pulmonary function tests if respiratory symptoms develop
  • Ophthalmologic examination if visual symptoms occur

Side Effects and Management

Side effects are extremely common (occurring in up to 93% of patients) and often dose-related 3, 4:

• Common side effects:

  • Gastrointestinal: constipation, nausea, anorexia
  • Neurological: tremor, ataxia
  • Ocular: corneal microdeposits, visual halos
  • Dermatological: photosensitivity
  • Cardiovascular: bradycardia, QT prolongation
  • Pulmonary: interstitial infiltrates, fibrosis
  • Thyroid dysfunction

• Management of side effects:

  • Dose reduction is often effective in managing side effects 5, 4
  • Maintain potassium and magnesium levels >4.0 mEq/L 1
  • Consider drug discontinuation for severe toxicity (particularly pulmonary)

Clinical Pearls and Pitfalls

• Important considerations:

  • Amiodarone has an extremely long half-life (average 58 days), requiring careful loading and monitoring 1
  • Bioavailability is variable (22-95%) and enhanced when taken with food 1
  • Drug interactions are significant due to inhibition of multiple CYP450 enzymes 1

• Key drug interactions requiring dose adjustments:

  • Warfarin: reduced clearance, monitor INR closely
  • Digoxin: levels may double
  • Statins: limit simvastatin to 20 mg daily
  • Other medications metabolized by CYP 2C9, CYP 2D6, and CYP 3A4

• Contraindications:

  • Severe sinus node dysfunction
  • AV block (without pacemaker)
  • Cardiogenic shock
  • Severe bradycardia

• Discontinuation: Consider after 6-12 months arrhythmia-free or if significant toxicity develops; taper rather than abrupt discontinuation 1