In managing a patient on clozapine, what side effect warrants close monitoring?

Clozapine is an atypical antipsychotic that is particularly effective for treatment-resistant schizophrenia. However, it carries a significant risk of agranulocytosis, which is a potentially life-threatening reduction in the number of white blood cells, specifically neutrophils. This side effect can lead to increased susceptibility to infections. Therefore, patients on clozapine require regular monitoring of their absolute neutrophil count (ANC) to ensure that their white blood cell levels remain within a safe range.

The monitoring protocol typically includes baseline ANC measurements before starting clozapine, weekly monitoring for the first six months, and then every two weeks for the next six months. If the ANC drops below a certain threshold, clozapine treatment may need to be suspended, and alternative management strategies may be considered.

While cardiovascular events, gastrointestinal issues, and hepatotoxicity are important considerations in the overall management of patients on clozapine, agranulocytosis remains the most critical side effect requiring vigilant monitoring due to its direct threat to the patient's immune system and overall health.