Abstract
The Dutch Clozapine Collaboration Group is frequently asked for advice about the management
of clozapine-treated patients when infected with or vaccinated against SARS-CoV-2.
We provide state of the art information about the risks of SARS-CoV-2 infection for
patients on clozapine and we give advice on measures to be taken, especially in regard
to the monitoring of clozapine plasma levels, WBC count and differentiation during
COVID-19 and after vaccination. We present an overview of relevant editorials, observational
studies, and case studies, in which COVID-19 was reported in patients on clozapine.
Patients using clozapine may have a higher risk of infection than patients with schizophrenia
spectrum disorders (SSD) using other antipsychotics. SARS-CoV-2 infection can result
in a dangerous increase of clozapine plasma levels, and granulocytopenia and lymphocytopenia
(generally mild and short-term) may also occur, usually not as a result of clozapine
treatment. Clozapine intoxication, pneumonia and delirium are the main complications
of COVID-19 in patients on clozapine. In order to prevent clozapine intoxication,
reduction of the original dose by half is generally recommended in clozapine users
who contract COVID-19. When a cytokine storm is suspected in an advanced stage of
COVID-19, reduction by three quarters seems more appropriate. If COVID-19 patients
on clozapine develop granulocytopenia, SARS-CoV-2, rather than clozapine, should be
considered as the cause. Schizophrenia patients in general and clozapine users in
particular belong to a high-risk group that warrants early vaccination on a medical
indication.
Key words
antipsychotic drugs - schizophrenia - immune system - clozapine - COVID-19
