Quinidine-induced agranulocytosis.

In a 75-year-old man, agranulocytosis and septicemia developed after eight weeks of quinidine sulfate therapy. An IgG antibody requiring the presence of quinidine was shown by complement-dependent leukocytotoxicity and leukoagglutination reactions. The antibody did not cross-react with quinine and was active against WBCs obtained from normal subjects and from the patient himself.