antiarrhythmics (class I)
Last reviewed 01/2018
Class I comprises the sodium channel blockers.
Class I drugs are subdivided into three groups according to the effect each has on the duration of the action potential:
- class Ia: duration is increased
- class Ib: duration is decreased
- class ic: duration is unchanged
The upstroke of the action potential in myocytes is mediated by sodium - thus alteration of sodium flux has the most potent effect on ventricular arrhythmias.
Note that other texts may subdivide the class I antiarrhythmics on the basis of their kinetics - Ia being the fastest acting, etc.