Amodiaquine-induced agranulocytosis: drug inhibition of myeloid colonies in the presence of patient's serum.

We report a patient who developed agranulocytosis following exposure to three drugs: amodiaquine, pyrimethamine and dipyrone. The combination of amodiaquine with the patient's serum, obtained during the agranulocytosis, inhibited in vitro granulocyte-monocyte colony-forming unit (CFU-GM) growth of autologous and allogeneic marrow. These results support the view that amodiaquine-induced agranulocytosis is immune in nature. This in vitro approach may be used to study the mechanism of drug-induced agranulocytosis, especially when patients are exposed to multiple drugs.