Quinidine-induced agranulocytosis of abrupt onset

Drug-induced agranulocytosis is a clinical entity characterized by a selective reduction of circulating neutrophils, usually to a level less than 0.2 x 10(9)/l in relation to the administration of the drug. Quinidine is an antiarrhythmic agent widely used on an outpatient basis with some well-known hematological side effects. Its midterm administration has been related to a few cases of agranulocytosis. Herein, we describe the case of a 60-year-old man with atrial fibrillation who presented quinidine-induced agranulocytosis of abrupt onset only 3 days after the exposure to the drug, recovering normal levels of neutrophils during the 3rd hospitalization day. Pathogenic mechanisms are discussed.