The Use of in Vitro Technics to Study Drug-Induced Pancytopenia

The confirmation of drug-induced marrow aplasia is difficult since rechallenging the patient can lead to serious morbidity. We used marrow-culture technics to challenge in vitro the bone marrow of a patient with marrow aplasia after ingestion of quinidine. There was no clinical or laboratory evidence of quinidine-mediated destruction of erythrocytes, leukocytes or platelets. By contrast, use of quinidine in combination with the patient's serum substantially inhibited in vitro growth of allogeneic marrow granulocytic and erythroid series. Furthermore, use of quinidine in combination with acute-phase serum (but not acute-phase serum alone or quinidine in combination with recovery-phase serum) inhibited growth of the patient's marrow. This observation suggests that both a transient serum factor and quinidine were responsible for the marrow aplasia. These technics could be applied with minimal risk to similar patients and would permit in vitro rechallenge with the suspected drug.