Treating chemotherapy induced agranulocytosis with granulocyte colony-stimulating factors in a patient on clozapine

Background Clozapine is reserved for overcoming treatment resistance in schizophrenia. Malignancy is common in schizophrenia; however, there is limited evidence available on continuing clozapine with chemotherapy, with both having hematological adverse effects. Objective To report a case on the use of granulocyte colony-stimulating factor (G-CSF) in conjunction with clozapine and chemotherapy. Methods We searched PubMed for any available information on the use of granulocyte G-CSF with clozapine and chemotherapy. We report the case of a patient with schizophrenia who developed B-cell lymphoma and was treated with chemotherapy consisting of CHOP regimen, rituximab, and methotrexate. He was continued on clozapine and G-CSF. Results We did not find any reports on G-CSF use in conjunction with clozapine and chemotherapy. We found case reports and a case series on the use of G-CSF in clozapine rechallenge with clozapine-induced agranulocytosis with mixed results. In our patient on clozapine, the white blood cell counts reduced by chemotherapy, were successfully replenished with the use of filgrastim, a G-CSF. Conclusions With risks of psychosis relapse and exacerbation with discontinuing clozapine, the addition of G-CSF could be a useful aid in replenishing white cell counts lost to chemotherapy whilst continuing clozapine. However, further study is needed on this combination.