Why we use it
Amiodarone is the Swiss Army knife of antiarrhythmics. Officially class III (prolongs repolarization by blocking potassium channels), it also blocks sodium and calcium channels and has non-competitive beta-blocking effects. The result: broad coverage of both atrial and ventricular arrhythmias with relatively limited proarrhythmic risk for the patient with structural heart disease.
Indication in the lab
- VT/VF storm — first-line antiarrhythmic in modern ACLS for refractory shockable rhythms
- Hemodynamically tolerated VT during VT ablation when we need rhythm stability
- Atrial fibrillation / flutter with rapid response, including post-cardiac-surgery AF
- Pharmacologic conversion of new-onset AF in selected patients
- Bridge therapy in the days to weeks after ablation when blanking-period arrhythmias persist
Dose and route
Acute loading (VT/VF or unstable arrhythmia):
- 150 mg IV over 10 minutes (faster pushes for arrest scenarios — 300 mg IV push in VF)
- May repeat 150 mg every 10 minutes for breakthrough VT
Maintenance infusion:
- 1 mg/min for the first 6 hours
- Then 0.5 mg/min for 18 hours
- Total ~1 g in the first 24 hours
Administration tips:
- Use a central line for infusions > 1 hour (phlebitis with peripheral)
- In-line filter recommended per manufacturer guidance
- Compatible with D5W; not with normal saline at high concentrations (precipitation risk)
Onset and duration
- IV onset: minutes for ventricular rate control; rhythm conversion can take hours to days
- Steady state: only after prolonged loading
- Half-life: weeks to months — this is the headline. A patient discharged on PO amiodarone is still seeing effects weeks after stopping.
Monitoring
- Continuous ECG — watch QT prolongation; significant QT extension or U-wave appearance means hold
- BP — bolus-related hypotension is common, often from the polysorbate-80 vehicle as much as from the drug
- Telemetry for at least 24 hours after loading
- Liver function and TSH at baseline; ongoing labs for any patient continuing PO therapy
- Chest x-ray and pulmonary symptoms for chronic users
Side effects to watch for
Acute (in the lab):
- Hypotension — slow the infusion, give fluids, use phenylephrine if needed
- Bradycardia and AV block — especially with concomitant beta-blocker or calcium channel blocker
- Phlebitis at peripheral IV sites
- Torsades — rare with amiodarone despite QT prolongation, but possible
Chronic (for the patient going home on PO):
- Pulmonary toxicity — interstitial pneumonitis; ask about new cough or dyspnea
- Thyroid — both hypo- and hyperthyroidism (iodine-rich molecule)
- Hepatic — transaminitis, rarely hepatitis
- Ocular — corneal microdeposits (nearly universal, usually asymptomatic); rare optic neuropathy
- Skin — photosensitivity and blue-gray skin discoloration with long-term use
- Neurologic — tremor, ataxia, peripheral neuropathy
Drug interactions worth knowing
- Warfarin — INR jumps; reduce dose 30–50% when starting amiodarone
- Digoxin — levels rise; reduce digoxin dose 50%
- Statins — increased rhabdo risk, especially with simvastatin
- Beta-blockers / calcium channel blockers — additive bradycardia and AV block
- QT prolongers — additive risk
Reversal
No specific antidote. Bolus-related hypotension responds to slowing or stopping the infusion, fluids, and pressors. Bradycardia from amiodarone may need pacing — the long half-life means the effect won’t simply wear off.
Common pitfalls
- Bolusing too fast through a peripheral and watching the BP crash.
- Saving the infusion bag with NS — precipitates; use D5W.
- Forgetting to adjust warfarin and digoxin when sending the patient home on PO amio.
- Treating QT prolongation alone as a contraindication — amio’s torsades risk is genuinely low compared to other class III agents.
- Stopping amio at discharge and assuming the effect is gone — half-life is weeks.