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cardio:arrhythmias:amiodarone

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cardio:arrhythmias:amiodarone [2026/02/12 23:49] – created andrew2393cnscardio:arrhythmias:amiodarone [2026/02/12 23:51] (current) – andrew2393cns
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 ====== Amiodarone ====== ====== Amiodarone ======
  
-Amiodarone is a Class III antiarrhythmic with multi-class activity.+Amiodarone is a Class III antiarrhythmic with multi-class electrophysiologic effects.
  
 It blocks: It blocks:
  
-• Potassium channels (Class III effect) +• Potassium channels (Class III) 
-• Sodium channels (Class I effect) +• Sodium channels (Class I) 
-• Beta receptors (Class II effect) +• Beta receptors (Class II) 
-• Calcium channels (Class IV effect)+• Calcium channels (Class IV)
  
 Because of this broad activity, amiodarone is highly effective for both atrial and ventricular arrhythmias. Because of this broad activity, amiodarone is highly effective for both atrial and ventricular arrhythmias.
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 ===== Mechanism of Action ===== ===== Mechanism of Action =====
  
-Primary action:+Primary effect:
  
 • Blocks potassium channels • Blocks potassium channels
 • Prolongs Phase 3 repolarization • Prolongs Phase 3 repolarization
 +• Prolongs action potential duration
 • Prolongs QT interval • Prolongs QT interval
  
-Additional actions:+Additional effects:
  
-• Sodium channel blockade +• Sodium channel blockade → slows conduction 
-• Beta-blocking activity +• Beta-blocking activity → reduces sympathetic drive 
-• Calcium channel blockade+• Calcium channel blockade → slows AV node
  
-Net Effect:+Net Effects:
  
 • Slows conduction • Slows conduction
-• Prolongs refractory period+• Increases refractory period
 • Suppresses automaticity • Suppresses automaticity
  
-Unlike most QT-prolonging drugs, torsades risk is relatively low.+Despite QT prolongation, torsades risk is relatively low compared to other Class III agents.
  
 -------------------------------------------------------------------- --------------------------------------------------------------------
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 • Rhythm control • Rhythm control
-• Used when other agents fail+• Used when other agents fail or are contraindicated
  
 ---- ----
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 ==== Ventricular Tachycardia / Ventricular Fibrillation ==== ==== Ventricular Tachycardia / Ventricular Fibrillation ====
  
-• Hemodynamically stable VT+• Stable monomorphic VT
 • Recurrent VT • Recurrent VT
 • Cardiac arrest (ACLS) • Cardiac arrest (ACLS)
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 ---- ----
  
-==== Heart Failure with Arrhythmia ====+==== Structural Heart Disease / HFrEF ====
  
-• Preferred antiarrhythmic in HFrEF +• Preferred antiarrhythmic in systolic heart failure 
-• Safer than Class IC drugs in structural heart disease+• Safer than Class IC agents in structural heart disease 
 + 
 +→ [[cardio:heart_failure:start|Heart Failure Module]]
  
 -------------------------------------------------------------------- --------------------------------------------------------------------
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 • Extremely lipophilic • Extremely lipophilic
 • Very large volume of distribution • Very large volume of distribution
 +• Accumulates in fat and tissues
 • Long half-life (weeks to months) • Long half-life (weeks to months)
-• Slow onset and slow offset +• Requires loading dose
-• Accumulates in tissues +
- +
-Requires loading dose.+
  
-Effects persist long after discontinuation.+Effects may persist long after discontinuation.
  
 -------------------------------------------------------------------- --------------------------------------------------------------------
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 Pulmonary: Pulmonary:
 • Interstitial pneumonitis • Interstitial pneumonitis
-• Pulmonary fibrosis+• Pulmonary fibrosis (most serious long-term risk)
  
 Thyroid: Thyroid:
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 Ocular: Ocular:
-• Corneal deposits+• Corneal microdeposits
 • Optic neuropathy (rare) • Optic neuropathy (rare)
  
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 Cardiac: Cardiac:
 • Bradycardia • Bradycardia
-• QT prolongation (torsades uncommon)+• QT prolongation 
 +• Torsades (rare compared to other Class III agents)
  
 -------------------------------------------------------------------- --------------------------------------------------------------------
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 ===== Monitoring ===== ===== Monitoring =====
  
-Baseline and periodic:+Baseline and periodic monitoring:
  
 • Chest X-ray • Chest X-ray
-• Pulmonary function tests (if symptoms)+• Pulmonary function if symptoms
 • Thyroid function tests • Thyroid function tests
 • Liver function tests • Liver function tests
 • ECG • ECG
  
-Long-term therapy requires surveillance.+Long-term therapy requires structured surveillance.
  
 -------------------------------------------------------------------- --------------------------------------------------------------------
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 ===== Drug Interactions ===== ===== Drug Interactions =====
  
-Amiodarone inhibits multiple CYP enzymes.+Amiodarone inhibits multiple CYP enzymes and P-gp.
  
 Can increase levels of: Can increase levels of:
  
 • [[cardio:arrhythmias:digoxin|Digoxin]] • [[cardio:arrhythmias:digoxin|Digoxin]]
-• Warfarin+• [[anticoagulation:warfarin|Warfarin]]
 • Other QT-prolonging drugs • Other QT-prolonging drugs
  
-Careful monitoring required.+Dose adjustments and monitoring are often required.
  
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 • Higher torsades risk • Higher torsades risk
 • Renally cleared • Renally cleared
 +• Initiation monitoring required
  
 [[cardio:arrhythmias:dofetilide|Dofetilide]]: [[cardio:arrhythmias:dofetilide|Dofetilide]]:
 • Strict QT monitoring • Strict QT monitoring
-• Initiation in hospital+• Hospital initiation required
  
 Amiodarone: Amiodarone:
 • Most effective • Most effective
-• Most toxic +• Lowest torsades risk among Class III drugs 
-• Preferred in structural heart disease+• Highest systemic toxicity burden
  
 -------------------------------------------------------------------- --------------------------------------------------------------------
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 ✔ Class III with multi-class activity   ✔ Class III with multi-class activity  
-✔ Very long half-life  +✔ Extremely long half-life  
 ✔ Low torsades risk despite QT prolongation   ✔ Low torsades risk despite QT prolongation  
 ✔ Multi-organ toxicity   ✔ Multi-organ toxicity  
-✔ Preferred antiarrhythmic in HFrEF  +✔ Preferred in structural heart disease and HFrEF   
 +✔ Requires routine monitoring  
  
 -------------------------------------------------------------------- --------------------------------------------------------------------
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 → [[cardio:beta_blockers:sotalol|Sotalol]] → [[cardio:beta_blockers:sotalol|Sotalol]]
 → [[cardio:arrhythmias:dofetilide|Dofetilide]] → [[cardio:arrhythmias:dofetilide|Dofetilide]]
 +→ [[cardio:heart_failure:start|Heart Failure Module]]
 → [[cardio:intro:start|Return to Cardiovascular Modules]] → [[cardio:intro:start|Return to Cardiovascular Modules]]
cardio/arrhythmias/amiodarone.1770940191.txt.gz · Last modified: by andrew2393cns