Clozapine is the treatment of choice in treatment resistant schizophrenia (TRS). Neutropenia is a potential life threating adverse effect associated with Clozapine treatment and one of the common reasons leading to discontinuation of Clozapine treatment. Clozapine associated neutropenia can be managed with Lithium or Granulocyte Colony Stimulating factor (G-CSF).Clozapine rechallenge in patients may often seem necessary and should follow a careful and balanced risk-benefit analysis. We present a case of a patient with TRS on Clozapine who developed neutropenia which responded to Filgrastim add on therapy and was successfully continued with Clozapine treatment.

A 29 year old female with a diagnosis of Schizophrenia since age 22 years had poor response to 4 different antipsychotics and 2 episodes of Neutropenia on separate occasions with Clozapine treatment. An inpatient Clozapine rechallenge was trialled due to poor response to the ongoing antipsychotic treatment which resulted in a decrease in the absolute neutrophil count to 1.7 *109/Litre.

An MDT decision was taken to continue Clozapine treatment with add on Filgrastim due to the severe psychopathology and poor quality of life. As per the advice from the haematologist Filgrastim injections at a dose of 30 million International Units were commenced on pro re nata (prn) basis whenever ANC dropped below 2.0*109/Litre. This strategy was successful and the patient did not develop agranulocytosis. Her psychotic symptoms also improved significantly and the patient was discharged to the community rehabilitation team.

Clozapine is often the last resort in treating refractory psychotic symptoms and this option may get limited due to adverse effects like Neutropenia and agranulocytosis. Add on therapy with G-CSF has been used in Clozapine rechallenge with various success rate and most of the supporting data are derived from case reports and case series. It is worth noting that regular and prophylactic G-CSF in absence of low neutrophil count is avoided which could mask a developing Clozapine induced Neutropenia and result in a steep drop in neutrophils.

Add on therapy with Filgrastim is a viable option when considering Clozapine rechallenge with previous history of Clozapine induced Neutropenia. It is important that a haematologist is consulted and the patient is monitored closely throughout the treatment.