Failure of filgrastim to prevent severe clozapine-induced agranulocytosis.

Although a highly effective medication, the usage of clozapine is limited mostly by its 2.7% incidence of neutropenia. It is often a treatment of last resort for patients with severe psychiatric illnesses, and therefore often the only medication to which a patient has responded. There has thus been a great deal of interest in ways to continue the medication in spite of emergent blood dyscrasias. There have been several reports documenting the successful continuation of clozapine in spite of neutropenia by adding granulocyte colony-stimulating factors such as filgrastim. This strategy was unsuccessful for a 63-year-old man, resulting in severe, prolonged agranulocytosis. Although a promising strategy for such refractory patients, its inherent dangers should not be underestimated.