Amiodarone

Cordarone · Pacerone · Nexterone

Class III antiarrhythmic (multichannel: K, Na, Ca, β-blocker)

Multichannel blockade — primarily class III (K+ channel block → prolonged repolarization, increased refractory period), plus class I (Na+ block), class II (β-blocker), class IV (Ca²⁺ block) properties. Treats most supraventricular AND ventricular arrhythmias. Long elimination half-life (weeks–months) limits chronic use.

Indications

•Refractory VF/pulseless VT during cardiac arrest (after CPR + 1st defib + epi)
•Stable monomorphic VT
•Atrial fibrillation/flutter rate + rhythm control (when other agents fail)
•Recurrent ICD shocks
•Supraventricular tachycardia

Dosing

Context	Adult	Pediatric
Cardiac arrest VF/pulseless VT	300 mg IV bolus, then 150 mg q3–5 min × 1 (max 2.2 g/24 h)	—
Stable VT/AF	150 mg IV over 10 min, then 1 mg/min × 6 h, then 0.5 mg/min × 18 h	—
Pediatric pulseless VT/VF		5 mg/kg IV bolus
Pediatric stable VT		5 mg/kg IV over 20–60 min, may repeat to 15 mg/kg/day

Pharmacokinetics

IV onset minutes; full effect hours to days. Massive volume of distribution (highly lipophilic — accumulates in fat, liver, lung). Half-life 25–110 days (chronic). Hepatic CYP metabolism, biliary excretion. Multiple drug interactions via CYP3A4 inhibition.

Hemodynamic effects

Modest hypotension (vasodilation from solvent excipient + Ca²⁺ blockade); bradycardia; minimal direct inotropy reduction. Less negative inotropy than other Class III antiarrhythmics. Older formulations (with polysorbate 80) cause more hypotension than aqueous Nexterone.

Side effects

!ACUTE: hypotension (bolus too fast), bradycardia, AV block
!Pulmonary fibrosis (chronic — 5–15% of long-term users)
!Hepatotoxicity (chronic — LFT elevation)
!Thyroid: hypo OR hyperthyroidism (iodine content 37%)
!Corneal microdeposits (asymptomatic, common)
!Photosensitivity, blue-gray skin discoloration
!QT prolongation (rare TdP given multichannel effect)

Contraindications

×2nd/3rd degree AV block (without pacemaker)
×Sinus node dysfunction with bradycardia
×Cardiogenic shock (relative)
×Iodine allergy (rare; cross-reactivity uncommon but documented)

Clinical pearls

★Code dose: 300 mg IV push for VF/pulseless VT after 1st defibrillation + epinephrine (per AHA ACLS).
★DILUTION: bolus must be diluted (5% dextrose for older formulation; aqueous Nexterone OK in either D5 or NS) — undiluted causes severe phlebitis.
★AF cardioversion: 150 mg load + infusion; conversion can take hours. Patient should already be anticoagulated if AF >48 h (TEE-guided alternative).
★DRUG INTERACTIONS via CYP3A4 inhibition: warfarin (↑INR), digoxin (↑levels — halve dose), simvastatin (rhabdo), amiodarone affects nearly everything chronic patients take.
★Postop new AF in cardiac surgery: amiodarone 150 mg load + 1 mg/min × 6 h often works when β-blockade doesn't.
★Use Nexterone (aqueous, sulfobutylether-β-cyclodextrin solubilizer) over older Cordarone for HD-stable patients — less hypotension on bolus.