From the Guidelines
Clozapine is the antipsychotic medication most strongly associated with cytopenia, a condition characterized by a low count of blood cells, particularly agranulocytosis, which occurs in approximately 1% of patients and is potentially fatal 1.
Key Points
- Clozapine requires an extensive monitoring protocol, including weekly blood cell counts during the first 6 months of treatment, and every 2 weeks thereafter, to mitigate the risk of agranulocytosis 1.
- Although primarily associated with clozapine, agranulocytosis can occur with any antipsychotic agent, with case reports of leukocytopenia in patients receiving risperidone and quetiapine 1.
- The risk of cytopenia with other atypical antipsychotics, such as olanzapine, is not as well established, but they are generally considered to be safer than clozapine 1.
- Pharmacogenetics may offer a way to optimize treatment approaches and reduce the risk of adverse effects, including cytopenia, in the future 1.
- The World Health Organization recommends that clozapine be considered for individuals who do not respond to other antipsychotic medicines, but only if routine laboratory monitoring is available 1.
From the Research
Antipsychotics Associated with Cytopenia
The following antipsychotics have been associated with cytopenia, a condition characterized by a low count of blood cells:
- Olanzapine: associated with neutropenia in several studies 2, 3, 4
- Quetiapine: associated with neutropenia in several studies 2, 3, 4
- Risperidone: associated with neutropenia in several studies 2, 3, 4
- Aripiprazole: associated with neutropenia in one study 2
- Paliperidone: associated with neutropenia in one study 5
- Clozapine: known to induce neutropenia and agranulocytosis, with a higher risk of hematologic toxicity compared to other antipsychotics 6, 3, 4
Risk of Neutropenia with Antipsychotics
The risk of neutropenia with antipsychotics is not limited to clozapine, and other antipsychotics such as olanzapine, quetiapine, and paliperidone have also been associated with this condition 6, 5, 4.
- A meta-analysis of controlled studies found that the risk of neutropenia was not significantly increased with clozapine compared to other antipsychotic medications 6
- A prospective investigation found that neutropenia occurred in 17.6% of patients treated with second-generation antipsychotics other than clozapine, and in 11.8% of patients treated with clozapine 3
- A case series of 18 patients with clozapine-associated granulocytopenia found that switching to another antipsychotic such as olanzapine or quetiapine may not solve the problem, as these medications can also cause prolonged leukopenia 4
Monitoring of White Blood Cell Counts
Monitoring of white blood cell counts is essential for patients treated with antipsychotics, especially those with a history of neutropenia or agranulocytosis 2, 3, 4.
- Close monitoring of white blood cell counts on a daily basis for the first 2 weeks after switching to another antipsychotic is recommended 4
- Patients treated with antipsychotics such as olanzapine, quetiapine, and paliperidone should be closely monitored for signs of neutropenia or agranulocytosis 5, 4