Prevalences of and characteristics associated with single- and polydrug-involved U.S. Emergency Department Visits in 2018

•We examined drug poisoning diagnosis codes in 2018 emergency department (ED) data.•Opioids, benzodiazepines, and stimulants were commonly involved in overdoses.•Nearly 17% of drug overdoses were polydrug, involving ≥ 2 drug classes.•Polydrug overdoses often involved benzodiazepines, opioids, and/or stimulants.•Hospitalization and death were more common among polydrug overdose ED visits.