Skip to main content

Is a "B52" appropriate for sedation when midazolam is ineffective?

Question#: 656


I was sedating a combative non-oriented pt in order to get them to the hospital safely. They were on Clonazepam, which is probably why they didn't have an adequate sedation with 7.5mg IM.

Should I patch for Diphenhydramine for sedation in this case? B52s are still widely used in hospitals and this would allow us to have a similar tool to that, save for Haldol and utilizing Midazolam rather than Lorazepam


 A "B52" is the co-administration of an anticholinergic, a benzodiazepine and a first generation antipsychotic (typically diphenhydramine, lorazepam and haloperidol) , to provide sedation for a severely agitated patient. The inclusion of diphenhydramine was to reduce possible adverse events and not primarily for its sedation properties. Co-administration of diphenhydramine in sedation has been found to increase duration of sedation and adverse events without providing an actual benefit, and is, therefore, not recommended.

Paramedics in Ontario have midazolam, ketamine and haloperidol available as sedatives. Diphenhydramine is NOT considered a useful sedative in the acute setting.

Midazolam is the first choice for acute management of patients presenting with severe agitation, especially if the cause is unknown.

Ketamine is indicated for patients with excited delirium or severely violent psychosis. Ketamine is useful when midazolam has failed to sedate or calm a severely agitated patient. The use of ketamine for an agitated patient who is not presenting with excited delirium or severely violent psychosis is outside of the medical directive conditions for administration, therefore, a patch to a BHP is required.

Haloperidol is a useful sedative, either alone or in combination with midazolam, for patients with known psychotic or psychiatric disorder presenting with severe agitation. However, at this stage, the MOH has explicitly restricted paramedic use of haloperidol to patients in the palliative program; therefore, it is not available for use in the general patient population.

Patient Care Standards:
Combative Patient Medical Directive

Campillo, et al. 2012. 416 The B52 Combination Is Not Frequently Used in Emergency Departments and Causes A High Proportion of Patients to Fall Asleep
Jeffers, et al. 2022. Efficacy of Combination Haloperidol, Lorazepam, and Diphenhydramine vs. Combination Haloperidol and Lorazepam in the Treatment of Acute Agitation: A Multicenter Retrospective Cohort Study.
Lexicomp: Diphenhydramine.
Moore, et al. 2022. Assessment and emergency management of the acutely agitated or violent adult. UpToDate.


31 January 2023



Please reference the MOST RECENT ALS PCS for updates and changes to these directives.