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. 2023 Jan 3;49(1):53-67.
doi: 10.1093/schbul/sbac148.

Clozapine Therapy and COVID-19: A Systematic Review of the Prevalence Rates, Health Outcomes, Hematological Markers, and Patient Perspectives

Grace Giles  1 , Sunny Varghese  1 , Gordon Shymko  1 , Thinh Nguyen  1   2 , Flavie Waters  2   3   4
Affiliations

Clozapine Therapy and COVID-19: A Systematic Review of the Prevalence Rates, Health Outcomes, Hematological Markers, and Patient Perspectives

Grace Giles et al. Schizophr Bull. .

Abstract

Background/objectives: There have been concerns that clozapine treatment may undermine the capacity of the body to fight infection and increase the vulnerability to contracting COVID-19. This review of recent cohort studies investigated (1) whether people with a severe psychiatric disorder are at increased risk of COVID-19 and complications, (2) the immunological response of clozapine-users who contract COVID-19, and (3) patients' perspectives on COVID-19 and the pandemic response.

Methods: A systematic search of EMBASE, Medline, Pubmed, and PsycINFO databases using PRISMA guidelines using "COVID-19", "clozapine", and "vaccination" terms.

Results: 18 studies (out of 330 identified) met all criteria (N = 119 054 including 8045 on clozapine). There was no strong evidence that clozapine users may be at increased risk of contracting COVID-19 or developing complications after adjusting for medical comorbidities. Hematological studies showed temporary reductions in neutrophils in COVID-19-positive patients and vaccination suggesting a clozapine effect in defence against infection. Vaccination studies did not report major adverse effects. Increased plasma levels of clozapine and neutropenia however point to COVID-19-related interference of clozapine metabolism. Patient surveys reported limited impact on mental health and positive attitudes regarding pandemic response.

Conclusion: This review did not find compelling evidence that the immune system of clozapine users put them at risk of COVID-19 and further complications. Evidence of drug-infection interactions however points to the importance of adhering to consensus guidelines about clozapine therapy during the pandemic. More evidence using longitudinal designs is required to examine the longer-term effects of COVID-19 and vaccination in this vulnerable population.

Keywords: COVID-19; clozapine; coronavirus; schizophrenia.

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Figures

Fig. 1.
Fig. 1.
Flowchart of systematic literature review.
Fig. 2.
Fig. 2.
Recommendations regarding COVID-19 and patients on clozapine therapy.
See this image and copyright information in PMC

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