QRS widening on tox screen
Drug-induced wide-complex
Mnemonic device
Na-channel blockers
Mapping
Tricyclics
TCAs (amitriptyline, nortriptyline) — Na-channel blockade; treat with bicarb 1-2 mEq/kg
Class 1A/1C
Quinidine, procainamide, flecainide — Na-channel blockade
Cocaine
Local anesthetic Na-channel blockade + sympathomimetic; benzos + bicarb, avoid β-blockers alone
Diphenhydramine
TCA-like Na-channel blockade at high doses
Hyperkalemia
Not a drug but causes the same wide-QRS picture; calcium first
Clinical note: Sodium bicarbonate 1-2 mEq/kg is the unifying treatment for Na-channel toxicity — overdrives the block + alkalinizes serum.