Generic antiarrhythmics are not therapeutically equivalent for the treatment of tachyarrhythmias.

The consequences of antiarrhythmic drug formulation substitution were assessed by survey of 130 experts on arrhythmias. Fifty-four arrhythmia recurrences, 7 proarrhythmic events, and 3 deaths resulting from generic substitution are reported, thus raising serious concerns about both antiarrhythmic drug substitution and the adequacy of the generic drug approval process.