Sodium channel blocker
Sodium channel blockers are drugs which impair conduction of sodium ions (Na+) through sodium channels.
The following naturally-produced substances block sodium channels by binding to and occluding the extracellular pore opening of the channel:
Drugs which block sodium channels by blocking from the intracellular side of the channel include:
Sodium channel blockers are used in the treatment of cardiac arrhythmia. They are classified as "Type I" in the Vaughan Williams classification.
Class I antiarrhythmic agents interfere with the (Na+) channel. Class I agents are grouped by their effect on the Na+ channel, and by their effect on cardiac action potentials. Class I agents are called Membrane Stabilizing Agents. 'Stabilizing' refers to the decrease of excitogenicity of the plasma membrane effected by these agents. A few class II agents, propranolol for example, also have a membrane stabilizing effect.
Class Ia agents block the fast sodium channel, which depresses the phase 0 depolarization (i.e. reduces Vmax), which prolongs the action potential duration by slowing conduction. Agents in this class also cause decreased conductivity and increased refractoriness.
Indications for Class Ia agents are supraventricular tachycardia, ventricular tachycardia, symptomatic ventricular premature beats, and prevention of ventricular fibrillation.
Procainamide can be used to treat atrial fibrillation in the setting of Wolff-Parkinson-White syndrome, and to treat wide complex hemodynamically stable tachycardias. Oral procainamide is no longer being manufactured in the US, but intravenous formulations are still available.
...
Wikipedia