Notes from the Field: Antihistamine Positivity and Involvement in Drug Overdose Deaths — 44 Jurisdictions, United States, 2019–2020

Abstract

Antihistamines are frequently used to treat allergy symptoms (1). Misuse of antihistamines has been documented primarily in adolescents and young adults (2); however, antihistamine involvement in overdose deaths has not been widely studied. Among the various antihistamine subtypes, the first-generation H1 subtype can cause anticholinergic effects, including strong sedation (3) that might be exacerbated when co-used with other sedative drugs (e.g., opioids).* Diphenhydramine, a common over-the-counter first-generation H1 antihistamine, has been combined with opioids as an adulterant† in illicit drug supply (4) and can be used to reduce opioid-related side effects (e.g., itchy skin because of histamine release from opioid use).