Drug Interactions between Clozaril and sars-cov-2 (covid-19) mrna-1273 (6m-5y bivalent booster) vaccine

Consumer information for this interaction is not currently available.

MONITOR: SARS-CoV-2 (COVID-19) vaccines may increase the serum concentrations and adverse effects of clozapine. In one case report, a 51-year-old male with schizoaffective disorder on long-term clozapine (500 mg/day, recently reduced to 300 mg/day after a hospital admission for pneumonia) was hospitalized 4 days after receiving the Pfizer-BioNTech COVID-19 vaccine (2020 - 2021). His clozapine dose was subsequently reduced to 150 mg/day. Upon further investigation, the patient's laboratory test results were consistent with inhibition of CYP450 1A2. The authors theorized that inhibition of drug metabolizing enzymes, including CYP450 1A2, may have been triggered by inflammatory processes from the pneumococcal infection as well as the COVID-19 vaccination. A 2021 multicenter observational cohort study (n=139) observed clinically relevant increases in clozapine blood levels (>100 mcg/L) in 20 patients (22%) after the first COVID-19 vaccine dose and 16 patients (29%) after the second dose. Changes in white blood cell counts for the patients observed in this study did not result in any clinical implications. However, the occurrence of neutropenia or leukopenia in patients on clozapine following the receipt of a COVID-19 vaccine has been documented in other case reports.

MANAGEMENT: SARS-CoV-2 (COVID-19) vaccination is generally both indicated and safe in patients treated with clozapine. However, these patients may benefit from careful evaluation for and additional counseling on signs and symptoms of clozapine toxicity as well as continued monitoring of clozapine levels as indicated.