Add-on filgrastim during clozapine rechallenge unsuccessful in preventing agranulocytosis

Granulocyte colony-stimulating factor agents such as filgrastim can be administered in order to reduce the duration of clozapine-induced agranulocytosis. Successful long-term combination treatment with filgrastim and clozapine in patients with previous clozapine-induced agranulocytosis has been described in several cases. We describe a patient with schizophrenia who developed agranulocytosis during treatment with clozapine and who did not respond to other antipsychotics. Add-on treatment with filgrastim during a clozapine rechallenge did not prevent the reoccurrence of agranulocytosis, and clozapine treatment had to be discontinued. Our case suggests that add-on filgrastim is a therapeutic option when clozapine is rechallenged, but physicians should be aware of the potential dangers especially severe clozapine-induced agranulocytosis.