B52 (medical treatment)
A B52 is an intramuscular injection containing three medications: diphenhydramine (Benadryl), haloperidol (Haldol), and lorazepam (Ativan). The B stands for Benadryl, the 5 stands for 5 milligrams of haloperidol, and the 2 stands for 2 milligrams of lorazepam. This injection is used to treat agitation.{{cite journal |vauthors=Jeffers T, Darling B, Edwards C, Vadiei N |title=Efficacy of Combination Haloperidol, Lorazepam, and Diphenhydramine vs. Combination Haloperidol and Lorazepam in the Treatment of Acute Agitation: A Multicenter Retrospective Cohort Study |journal=J Emerg Med |volume=62 |issue=4 |pages=516–523 |date=April 2022 |pmid=35287982 |doi=10.1016/j.jemermed.2022.01.009 |url=}} Haloperidol is included because it "blocks dopamine receptors, which may relieve agitation." Lorazepam is included because it "enhances GABA inhibitory action to relieve anxiety and cause sedation." 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.{{cite journal |vauthors=Gautam M, Patel S, Sablaban I |title=Intramuscular B52 |journal=Prim Care Companion CNS Disord |volume=23 |issue=3 |pages= |date=May 2021 |pmid=34015196 |doi=10.4088/PCC.20br02855 |url=http://www.psychiatrist.com/pcc/intramuscular-b52}}
Diphenhydramine is included upon the rationale that it "provides sedation and reduction of dystonia from haloperidol."{{cite journal |vauthors=Sunshine N, Martinez J, Bazan A, Wolowich WR, Zitek T |title=Ketamine Versus Haloperidol/Lorazepam/Diphenhydramine Combination Treatment for Management of Acute Agitation in the Emergency Department |journal=Open Access Emerg Med |volume=17 |issue= |pages=113–120 |date=2025 |pmid=39981414 |pmc=11840334 |doi=10.2147/OAEM.S486208 |doi-access=free |url=}} However, evidence presented in a 2022 retrospective cohort study 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.{{Cite web |last1=Hayes |first1=Bryan |last2=O'Brien |first2=Mike |date=April 16, 2022 |title=Should Diphenhydramine be included in an Acute Agitation Regimen? |url=https://www.aliem.com/diphenhydramine-acute-agitation-regimen/ |access-date=April 18, 2025 |website=Academic Life in Emergency Medicine}} The diphenhydramine component of B52 is also associated with lower oxygen levels and the use of physical restraints.{{cite journal |vauthors=Strayer RJ |title=Management of Pain and Agitation in Trauma |journal=Emerg Med Clin North Am |volume=41 |issue=1 |pages=117–129 |date=February 2023 |pmid=36424036 |doi=10.1016/j.emc.2022.09.003 |url=https://emupdates.com/wp-content/uploads/2022/11/Strayer-2022-Management-of-Pain-and-Agitation-in-Trauma-EMCNA.pdf}}