Coadministration of intramuscular olanzapine and benzodiazepines in agitated patients with mental illness

Intramuscular antipsychotics are commonly used to manage agitated patients. In 2005, Eli Lilly placed a warning on olanzapine's prescribing information following post-marketing reports of fatal drug reactions when intramuscular olanzapine was used in the setting of benzodiazepines. Data is lacking examining this drug combination.

A medication use evaluation was conducted at a county psychiatric hospital surveying the usage of concomitant intramuscular olanzapine and lorazepam from October 1, 2016, to July 20, 2017. A literature search was conducted to review available evidence.

Ninety-one instances of the drug combination were discovered, with no serious adverse events following administration. Of these 91 patients, 41 received both medications within 60 minutes of each other. No instances of hypotension, bradycardia, bradypnea, or oxygen desaturation occurred following administration. The literature review yielded 1 randomized, placebo-controlled clinical trial, 3 retrospective chart reviews, and several case studies.

Data detailing a causal relationship between olanzapine/benzodiazepine combinations and serious adverse effects is lacking. Available evidence does not consistently support a strong cause and effect relationship. The results of this medication use evaluation are not consistent with the Food and Drug Administration warning. Further controlled research is needed to help define the actual risk of using concomitant intramuscular olanzapine and benzodiazepines.