Haematological side effects associated with clozapine: A retrospective study from India

To evaluate the incidence of clozapine induced haematological side effects among patients receiving clozapine.

Data of 333 patients who were on clozapine for a mean duration of 52.96 (45.18) months were reviewed for haematological abnormalities.

Most of the patients (n = 320; 96.1 %) were diagnosed with psychotic disorders, mainly schizophrenia. These patients were receiving clozapine in the dose range of 12.5 mg-600 mg/day, with a mean dose of 212.08 (102.43) mg/day at the time of review of their records. About one-tenth (N = 33; 9.9 %) of patients developed eosinophilia (absolute eosinophil count >600), and 8.2 % (N = 27) experienced thrombocytopenia (platelet count <100,000 cmm³) and 7 patients developed anaemia (haemoglobin level <10 gm%). Only 2 (0.6%) patients developed neutropenia. Mean dose (mg/day) at which haematological side-effects occurred were as follows: 159.85 (87.65) mg/day for eosinophilia; 193.98 (148.93) mg/day for thrombocytopenia; 78.57 (22.49) mg/day for anaemia. In a small proportion of patients, clozapine was discontinued due to the haematological abnormalities and in other patients these abnormalities normalized on its own in subsequent follow-up.

Clozapine is associated eosinophilia and thrombocytopenia, which are often benign and in majority of the patients these normalize with time.