The differences with which the class I drugs dissociate from the sodium channel identify the three sub groups labeled Ia,Ib and Ic. The type Ib drugs, lidocaine and mexilitine, dissociate most rapidly and exhibit the least use or rate dependency. The type Ic drugs, flecainide, encainide and propafenone (SHOULD ENCAINIDE BE OMITTED?) dissociate most slowly and exhibit the greatest use or rate dependency. The Ib drugs, quinidine disopyramide and procainamide are intermediate in their effect. Amiodarone’s use dependent effect on the sodium channel is similar to that of the class Ia drugs
