What condition must be monitored before starting Clozapine?

Before initiating treatment with Clozapine, it is essential to monitor the Absolute Neutrophil Count (ANC) due to the risk of agranulocytosis, a potentially life-threatening side effect. Clozapine is known for its efficacy in treatment-resistant schizophrenia, but its use is limited by this serious adverse effect, which can lead to a drastically reduced white blood cell count.

Clinicians must ensure that a patient’s ANC is within a safe range prior to starting Clozapine, typically requiring an ANC of 1500 cells/mm³ or higher. This monitoring process typically involves baseline measurements and ongoing monitoring during treatment as per established guidelines to mitigate serious risks.

Monitoring is not typically required for blood pressure, liver function, or renal function prior to starting Clozapine, although these factors may be relevant throughout treatment for other reasons. However, the primary concern directly related to Clozapine's safety profile is the white blood cell count, specifically the ANC.