Which condition is a contraindication for prescribing clozapine?

Clozapine is an antipsychotic medication that is particularly effective in treatment-resistant schizophrenia but comes with significant risks, particularly related to the bone marrow. One of the most severe side effects of clozapine is agranulocytosis, which is a potentially life-threatening reduction in the number of white blood cells.

Bone marrow depression is a contraindication for prescribing clozapine because if a patient already has a compromised bone marrow function, the use of clozapine could exacerbate this condition, leading to an increased risk of severe infection due to low white blood cell counts. Therefore, before initiating treatment with clozapine, it is crucial to assess the patient's hematological status to avoid any serious complications that may arise from further suppression of bone marrow activity.

While high blood pressure, diabetes, and heart disease may pose risks or require careful monitoring when using clozapine, they do not fundamentally prevent the use of the medication in the same way that bone marrow depression does. The direct effects of clozapine on blood cell counts make bone marrow depression a critical consideration that necessitates avoiding this medication.