Class 1A Antiarrhythmics

Class 1A Antiarrhythmic drugs prolong the refractory period and slow conduction of electrical impulses.  Class 1A drugs work by blocking fast sodium channels, which prolongs phase 0 depolarization.  Prolonging phase 0 reduces conduction velocity and increases the refractory period.  These effects decrease myocardial excitability. These medications are not widely used; however, procainamide can be used in the treatment of atrial fibrillation/flutter in the setting of Wolff-Parkinson-White syndrome.

Class Drugs

• Quinidine

• Procainamide

• Disopyramide

Class Mechanism of Action

Blocks voltage sensitive sodium channels

• Slows phase 0 in ventricle

Potassium channel inhibition

• Slows phase 3 and increases effective refractory period

Calcium channel blocker

Anticholinergic

Class IA Antiarrhythmics diagram

Class Applications

Treatment of tachy-arrhythmias

• Atrial

• AV junctional

• Ventricular

Class Adverse Effects

• Anticholinergic effects (dry mouth, urinary retention, etc.)

Drug Table

Drug Name	Application	Comments	Image
Quinidine	Maintenance of sinus rhythm after conversion from atrial fibrillation/flutter; Suppression of ventricular tachycardia and ventricular ectopic beats; Malaria	Mechanism; In addition; Alpha blocking effects; Adverse Effects; Cinchonism - tinnitus, blurred vision, diarrhea; Prolonged QT, ventricular arrhythmias; Thrombocytopenia; Skeletal muscle weakness; Hypotension; Drug Interactions: digoxin, warfarin	"Quill" "Dining Table"
Procainamide	Atrial fibrillation or flutter in setting of Wolff-Parkinson-White syndrome	Pharmacokinetics; Active metabolite present:; -NAPA (N-acetylprocainamide) is produced in the liver and acts as a Class III antiarrhythmic drug; Adverse Effects; May cause hypotension; Lupus-like syndrome	"Professional" "Cain"
Disopyramide	Rarely used. May be used in maintenance of sinus rhythm in atrial fibrillation or atrial flutter.; Also used as an alternative to procainamide or quinidine	Adverse Effects; Negative inotropic effect, which may cause dysfunction in patients with systolic heart failure	"Dice" "Pyramid"