84: Chemical sedation for acute agitation

In this episode I’ll discuss chemical sedation for acute agitation.
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Chemical sedation is part of the array of options to treat acute agitation. Prevention strategies, verbal de-escalation techniques, and physical restraints also play a role in the prevention and management of acute agitation.

The ideal first line medications to use for rapid tranquilization of an acutely agitated patient are benzodiazepines and antipsychotics. These medications may be given alone or in combination.

Evidence for the use of chemical sedation is limited to small trials of at most a few hundred patients. Midazolam or lorazepam are the most studied benzodiazepines and haloperidol or droperidol are the most studied antipsychotics. Generally, control of the patient’s agitation is achieved within 15-20 minutes with these medications. The main side effect to monitor and be prepared for is respiratory depression.

Drug selection based on cause of agitation

Unknown

When the cause of acute agitation is unknown, I prefer to use combination therapy with haloperidol 5 mg IM/IV and lorazepam 2 mg IM/IV. This combination works faster than using either drug alone. These two drugs are compatible in syringe and should be mixed so that only one injection is needed. Many providers at my institution add 50 mg of diphenhydramine to the syringe, and call the combination a “B-52” for Benadryl + 5 mg haloperidol + 2 mg lorazepam. The sedating properties of antihistamines are well established, but this combination has never been studied to my knowledge.

Ethanol intoxication

When the cause of acute agitation is ethanol intoxication, I prefer to use an antipsychotic such as haloperidol 5 mg IM/IV first. Benzodiazepines when given to a patient with ethanol intoxication may be more likely to cause respiratory depression.

Drug intoxication or withdrawal

When the cause of acute agitation is drug intoxication or withdrawal I prefer to use a benzodiazepine such as lorazepam 2 mg IM/IV. Antipsychotics can increase the seizure risk when given to patients in alcohol or benzodiazepine withdrawal, and can worsen anticholinergic toxicity.

Psychiatric disorder

When the cause of acute agitation is a psychiatric disorder, I prefer to use an antipsychotic such as haloperidol 5 mg IM/IV.

Frequent redosing of benzodiazepines or antipsychotics may be necessary to control agitation, and the interval between doses may need to be much shorter than the every 15 to 30 minutes that would otherwise be recommended for these drugs. Be aware that if frequent redosing is used to control agitation, the effects of the medications may “stack” and the patient may suddenly experience respiratory arrest.

If excessive doses of benzodiazepines or antipsychotics are ineffective, ketamine may be used as a rescue treatment for acute agitation. The dose is 2 mg/kg IV or 5 mg/kg IM. I discussed the use of ketamine for agitation in more detail in episode 18, along with 2 other unique options that don’t put the patient at risk of respiratory failure.

I don’t usually use the atypical antipsychotics in acute agitation, but they may be useful if the patient is semi-cooperative and willing to take an oral dissolving tablet such as olanzapine. Although the parenteral formulation of olanzapine is labeled for IM use only, I discussed the evidence behind IV olanzapine for agitation back in episode 43.

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