Clinical predictors of repeat intramuscular medication administration for acute agitation: A retrospective cohort...

Intramuscular (IM) antipsychotics are frequently used for acute agitation in psychiatric settings. While prior studies have focused on onset of sedation and adverse effects, the need for repeat IM medication, an important real-world marker of treatment effectiveness, has not been well characterized.

This retrospective study included adult patients who received IM haloperidol lactate or IM olanzapine for acute agitation between January 2020 and November 2022 at an academic medical center. The primary outcome was repeat IM medication administration within 24 h. Secondary analyses examined time to repeat administration. Sociodemographic, clinical, and treatment-related variables were compared. Multivariable logistic regression and Cox proportional hazards models were used to identify independent associations.

Among 342 patients, 81 (23.7%) required repeat IM medication. Antipsychotic agent was not associated with repeat administration. In adjusted analyses, repeat medication was independently associated with co-administration of diphenhydramine (OR = 2.18), history of violence (OR = 1.88), and psychotic disorders (OR = 2.24), while substance use history (OR = 0.48) and inpatient setting (OR = 0.50) were associated with lower odds. Similar findings were observed in time-to-event analyses. Greater prior hospitalizations were associated with shorter time to repeat medication. Benzodiazepine co-administration was not independently associated with outcomes.

Repeat IM medication for acute agitation is common and appears to be driven primarily by patient-level factors rather than choice of antipsychotic agent. These findings highlight the importance of underlying illness severity and agitation phenotype in determining treatment response. Identifying patients at higher risk for escalation may inform targeted management strategies and resource allocation in acute psychiatric care settings.