Antiarrhythmic Agent Overdose

Class Ia antiarrhythmic agents

• Quinidine

• Disopyramide

• Procainamide

Class Ic antiarrhythmic agents

• Flecainide

• Propafenone

Arrhythmias

Syncope

Hypotension

Blood levels of quinidine and procainamide (and active metabolite NAPA) are generally available from hospital laboratory

ECG monitoring for QRS and QT interval prolongation

• Widening of the QRS complex (> 100–120 ms)

• With type Ia drugs, a lengthened QT interval and atypical or polymorphous ventricular tachycardia (torsades de pointes) may occur

Activated charcoal

• Administer 60–100 g orally or via gastric tube, mixed in aqueous slurry for ingestions within 1 h

• Do not use for comatose or convulsing patients unless they are endotracheally intubated

Consider gastric lavage for recent (1 h) large ingestions

Consider whole bowel irrigation for ingestion of sustained-release formulations

Perform continuous cardiac monitoring

Treat cardiotoxicity (hypotension, QRS interval widening) with intravenous boluses of sodium bicarbonate, 50–100 mEq

Torsades de pointes ventricular tachycardia may be treated with intravenous magnesium or overdrive pacing