class I antiarrhythmics

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.