University of Hertfordshire

Clozapine, neutropenia and Covid-19: should clinicians be concerned? 3 months report

Research output: Contribution to journalArticlepeer-review


  • Stefania Bonaccorso
  • Angelo Ricciardi
  • Sophie Ouabbou
  • Christos Theleritis
  • Arabella Ross-Michealides
  • Antonio Metastasio
  • Neil Stewart
  • Marwa Mohammed
  • Fabrizio Schifano
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Original languageEnglish
Article number100212
Number of pages4
JournalBrain Behavior and Immunity
Early online date28 Jan 2021
Publication statusPublished - May 2021


Background: Clozapine is among the most effective antipsychotics used for treatment resistant schizophrenia. Adverse reactions to clozapine include neutropenia. In March 2020, at the start of the Coronavirus -19 pandemic, clinicians raised concerns regarding continuation of antipsychotic treatment, and specifically of clozapine, in patients with coronavirus disease. We aimed here at providing a short report focusing on the association between neutropenia and clozapine in a case series of psychiatric inpatients diagnosed with COVID-19.Patients & methods: We retrospectively inspected data of 10 patients on clozapine, admitted to Highgate Mental Health Centre, Camden & Islington NHS Foundation Trust, between March and July 2020; selection was based on their COVID-19 positive PCR test. We used a linear regression model to estimate whether there was a significant drop in the neutrophil count during SARS-CoV-2 infection.The analysis was done in R using a linear regression to the origin.Results: Data were collected on 10 patients, of which 7 were males. During COVID-19 infection, neutrophils' count (ANC) was 4.13 ​× ​10 9/l (SD ​= ​2.70) which constituted a significant drop from a baseline value of 5.2 ​× ​10 9/l (SD ​= ​2.24). The mean relative reduction in ANC was -0.2729 (SD ​= ​0.1666). The beta value of 0.8377 obtained with the linear regression showed that ANC values during SARS-CoV-2 infection were 83.77% of the baseline ANC showing that within the two time points there was a decrease of 16.23%. The linear regression had a pvalue ​= ​8.96 ​× ​10 -8 and an adjusted R 2 of 95.94% which shows that the variability of the data is very well explained by the model. We also compared baseline ANC with ANC values approximately a month after resolution of the infection and results indicate that ANC values return to a 95% of baseline. Conclusions: Clinicians should bear in mind that a significant drop in neutrophils' count may occur in patients taking clozapine and affected from a SARS-CoV-2 infectionand that this drop is only transitory.


© 2021 Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (

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