Quinidine, procainamide, disopyramide
Class IA anti-arrhythmic (Na+ channel block during Phase 0 depolariz): prolongs AP conduction in bundle of His & Purkinje, also decreases automaticity of ventricular cells --> prolongs QRS & QT. For: Atrial arrhythmias, ventricular ectopic beats (disopyramide esp). SE's: HA, GI disturbance, cinchonism (tinnitus & blurred vision), torsades de pointes (b/c prolonged QT). Procainamide also causes agranulocytosis, neutro- & thrombocytopenia. Must pre-treat w/b-blocker, Ca++ channel blocker, or digitalis to slow ventricular response.