B52 (medical treatment)

A B52 is an intramuscular injection containing three medications: diphenhydramine (Benadryl), haloperidol (Haldol), and lorazepam (Ativan).^[1] The B stands for Benadryl, the 5 stands for 5 milligrams of haloperidol, and the 2 stands for 2 milligrams of lorazepam.^[2] This injection is used to treat agitation.^[3] Haloperidol is included because it "blocks dopamine receptors, which may relieve agitation."^[1] Lorazepam is included because it "enhances GABA inhibitory action to relieve anxiety and cause sedation."^[1] A 2021 review of B52 questioned the use of diphenhydramine in the cocktail given there was no evidence base found for its inclusion, whereas there was evidence for haloperidol and lorazepam.^[2]

Diphenhydramine is included upon the rationale that it "provides sedation and reduction of dystonia from haloperidol."^[1] However, evidence presented in a 2022 retrospective cohort study^[3] is used to argue against its inclusion, based on a low risk of extrapyramidal symptoms and an association with longer stays in the emergency room.^[4] The diphenhydramine component of B52 is also associated with lower oxygen levels and the use of physical restraints.^[5]