COVID-19: Clozapine Treatment Increases Risk for Infection

The risk for COVID-19 infection among clozapine-treated patients is elevated, according to researchers.

Patients treated with clozapine had an increased risk for coronavirus disease 2019 (COVID-19) infection. These findings, from a retrospective cohort study, were published in The British Journal of Psychiatry.

Researchers searched the South London and Maudsley (SLAM) National Health Service Foundation Trust clinical records for individuals with an International Classification of Diseases-10 diagnosis of schizophrenia-spectrum disorders who were taking antipsychotics (n=6309) between March 1 and May 18, 2020.

Mean patient age was 46.5±14.8 years (61.7% men; 50.6% Black, 33.2% white, 13.7% Asian, and 2.5% had missing ethnicity data). Within the cohort, 20.32% were taking clozapine. Among those on clozapine therapy, 80% were current smokers, and 48% were obese. Individuals on clozapine, compared with those not on clozapine, were more likely to be inpatients (13% vs 6%) and had received more SLAM services during the previous 3 months (≥8 days, 43.76% vs 30.83%), respectively.

Among patients who tested positive for COVID-19 infection, 41% were being treated with clozapine; among those who tested negative for COVID-19, only 20% were on clozapine treatment. The overall hazard ratio (HR) for testing positive for COVID-19 while receiving clozapine treatment was 2.62 (95% CI, 1.73-3.96).

After adjusting for the demographic features of age, gender, and ethnicity, the HR increased to 3.06 (95% CI, 2.01-4.67) for infection with COVID-19 among patients receiving clozapine. After adjusting for inpatient status and SLAM service contact, the HR decreased to 1.85 (95% CI, 1.20-2.85). Adjusting for body mass index and smoking status reduced the HR for COVID-19 infection among patients treated with clozapine to 1.76 (95% CI, 1.14-2.72).

Study limitations included an inability to decipher whether clozapine increased the likelihood of infection or the likelihood of a symptomatic infection. Without further study, it remains unclear whether the increased traffic to healthcare facilities was the source for the increased infection rate among clozapine recipients.

The study authors concluded that patients treated with clozapine were at higher risk for infection with COVID-19, which is in line with previous studies that have found an increased risk for pneumonia and other infections compared against patients treated with other antipsychotic drugs. Further research is needed to confirm these findings in order to develop clinical guidelines for the care of patients with schizophrenia-spectrum disorders during the global COVID-19 pandemic.

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.


Govind R, de Freitas DF, Pritchard M, Hayes RD, MacCabe JH. Clozapine treatment and risk of COVID-19 infection: Retrospective cohort study [published online July 27, 2020]. Br J Psychiatry. doi: 10.1192/bjp.2020.151