Agranulocytosis during combined procainamide and phenytoin therapy

We have presented two cases of agranulocytosis occurring in patients receiving a combination antiarrhythmic regimen. As multiple drug therapy for ventricular arrhythmias becomes more commonplace, increased scrutiny should be given to agents chosen, in an effort to prevent any possible adverse interactions. When future cases are encountered, the acetylator pheontype should be determined. This information would aid in assessing the predicative value of the acetylator phenotype in the development of agranulocytosis. Due to the inherent danger, neither patient was rechallenged with procainamide nor phenytoin.