(272) Emergency Department Visits due to Monoclonal Antibody Adverse Events—United States, 2004–2020

Background: The number of monoclonal antibody (mAb) products available has increased substantially in recent years. However, nationally representative data on mAb adverse events (AEs) in outpatient settings have not been available.

Objectives: To estimate the number of emergency department (ED) visits due to mAb AEs in the U.S. by patient characteristics and active ingredient.

Methods: Data from the nationally representative, National Electronic Injury Surveillance System-Cooperative Adverse Drug Event Surveillance (NEISS-CADES) project were analyzed. An AE case was defined as an incident ED visit for a condition or harm that the treating clinician explicitly attributed to the use of a drug, or a drug-specific effect based on the clinicians’ diagnoses and supporting data documented in the medical record. Exposures of interest for this analysis were mAb products approved by the U.S. Food and Drug Administration that were implicated in ED visits for AEs in NEISS-CADES from January 1, 2004 to December 31, 2020. National estimates and 95% confidence intervals (CIs) of ED visits and subsequent hospitalizations were calculated using SAS version 9.4. Annual national estimates were calculated by dividing the total estimates by the number of years in the study period.

Results: Based on 1310 cases, there were an estimated 64,037 (95% CI= 40,231, 87,844) ED visits due to mAb AEs from 2004–2020, and over one-third (37.3%; 95% CI=28.3%, 46.3%) of these visits resulted in hospitalization. The annual estimated number of ED visits due to mAb AEs increased 16-fold from 662 in 2004–2006 (95% CI=298, 1,026) to 10,809 in 2019–2020 (95% CI=5,005, 16,613). From 2004-2020, most (73.6%; 95% CI=68.4%, 78.9%) mAb AE visits involved adults aged ≥40 years, and 66.9% (95% CI=61.6%, 72.1%) involved females. Most visits (80.9%; 95% CI=73.1%, 88.7%) only involved a single mAb product and did not involve additional implicated products (i.e., prescription and over-the-counter medications, dietary supplements, homeopathic products, or vaccines). The five most frequently implicated mAb products in ED visits for AEs were rituximab (19.5%; 95% CI=16.4%, 22.6%), infliximab (17.8%; 95% CI=13.5%, 22.2%), adalimumab (11.9%; 95% CI=8.4%, 15.4%), bevacizumab (6.5%; 95% CI=3.8%, 9.2%), and pembrolizumab (4.7%; 95% CI=2.4%, 6.9%).

Conclusions: The marked increase in the number of ED visits due to mAb AEs in the period from 2004–2020 likely corresponds with increased use. Further characterization of AEs from specific mAb products and calculation of AE rates can help guide clinicians in assessing risks versus benefits when prescribing mAb products.