Class I Antiarrhythmics and their Key Pharmacologic Properties
Class IA = Quinidine, Procainamide, Disopyramide ("Quarter PounDer")
Class IB = Lidocaine, Tocainide, Mexiletine, Phenytoin ("Lettuce, Tomato, Mayo, Pickle")
Class IC = Flecainide, Propafenone ("Fries Please")
Block fast Na+ channels that are responsible for the rapid depolarization (phase 0) of fast-response cardiac action potentials. This type of action potential is found in non-nodal cardiomyocytes. This decreases conduction velocity in non-nodal tissue and serves as an important mechanism for suppressing tachyarrhythmias.
• Slows depolarization, results in wide QRS on EKG
• Na+ channel blockade: IC > IA > IB
Some increase the effective refractory period (ERP) due to their actions on K+ channels involved in phase 3 repolarization of action potentials.
• Prolongs repolarization and refractory period, results in prolonged QT on EKG
• Increasing the ERP: IA > IC > 1B (decreases)
#ClassI #Class1 #Antiarrhythmics #Pharmacology #Agents #Cardiology
