Time to retire haloperidol?

For more than half a century, haloperidol has been used as a first-line medication for psychiatric agitation constituting a “behavioral emergency” when a patient cannot or will not take oral medication. Today, haloperidol is most commonly administered as an IM injection along with an anticholinergic medication to minimize extrapyramidal symptoms (EPS) and a benzodiazepine for additional sedation. The multiple-medication “cocktail” is often referred to by double-entendre nicknames, such as “B-52” or “5250” (ie, haloperidol, 5 mg; lorazepam, 2 mg; and diphenhydramine, 50 mg). In this article, I discuss whether haloperidol, a first-generation antipsychotic (FGA) medication developed in 1958, still deserves to be the IM “gold standard” for managing emergency psychiatric agitation.

Earlier evidence of haloperidol’s efficacy

The initial “discovery” of antipsychotic medications was made in 1951 based on the inadvertent observation that chlorpromazine had the potential to calm surgical patients with autonomic activation. This calming effect, described as “désintéressment” (meaning a kind of “indifference to the world”),¹ resulted in a new class of medications replacing barbiturates and bromides as go-to options to achieve “rapid tranquilization” of psychiatric agitation.² Although the ability of antipsychotic medications to gradually reduce positive symptoms, such as delusions and hallucinations, has been attributed to dopamine (D2) antagonism, their more immediate sedating and anti-agitation effects are the result of broader effects as histamine (H1) and alpha-1 adrenergic antagonists.

In the 1970s, haloperidol emerged as a first-line option to manage agitation due to its IM and IV availability, as well as its relative lack of sedation and orthostasis compared with low-potency D2 antagonists such as chlorpromazine. However, haloperidol was observed to have a significant risk of acute EPS, including dystonic reactions.² From the 1970s to the 1990s, numerous prospective clinical trials of haloperidol for the treatment of acute psychotic agitation, including several randomized controlled trials (RCTs) comparing haloperidol to lorazepam, were conducted.³ The design and outcomes of the haloperidol vs lorazepam RCTs were fairly consistent^4-7:

• adult participants with acute agitation and a variety of psychiatric diagnoses, for whom informed consent often was waived due to agitation severity
• randomization to either IM haloperidol, 5 mg, or IM lorazepam, 2 mg, administered every 30 minutes until agitation resolved
• behavioral outcomes measured over several hours using various rating scales, without consistent assessment of EPS
• equivalent efficacy of haloperidol and lorazepam, with symptom resolution usually achieved after 1 to 2 doses (in 30 to 60 minutes), but sometimes longer
• anticholinergic “rescue” allowed for EPS, but not administered prophylactically
• EPS, including dystonia and akathisia, were significantly more frequent with haloperidol compared with lorazepam.⁸

In recognition of the greater risk of EPS with haloperidol compared with lorazepam, and the fact that most study participants were already taking standing doses of antipsychotic medications, some researchers have recommended using benzodiazepines alone as the optimal treatment for agitation.^4,9 A 2012 Cochrane review concluded that the involuntary use of haloperidol alone “could be considered unethical.”^10,11 However, other studies that examined the combination of haloperidol and lorazepam compared with either medication alone found that the combination of the 2 medications was associated with a more rapid resolution of symptoms, which suggests a superior synergistic effect.^6,7,12 By the late 1990s, combined haloperidol and lorazepam, often mixed within a single injection, became the most common strategy to achieve rapid tranquilization in the psychiatric emergency setting.¹³ However, while the combination has been justified as a way to reduce the antipsychotic medication dose and EPS risk,² few studies have compared combinations containing <5 mg of haloperidol. As a result, the apparent superiority of combined haloperidol and lorazepam compared with either medication alone may be a simple cumulative dose effect rather than true synergism. It is also important to note that adding lorazepam to haloperidol does not mitigate the risk of EPS such as dystonia in the absence of anticholinergic medication.⁸ To date, however, there have been no clinical trials investigating the efficacy of IM haloperidol, lorazepam, and benztropine or diphenhydramine given together.

Newer RCTs tell a different story

With the availability of second-generation antipsychotics (SGAs) in IM formulations, clinical trials over the past 2 decades have focused on comparing SGAs with haloperidol alone as the “gold standard” control for acute agitation. Compared with previous trials of haloperidol vs lorazepam, these clinical trials of SGAs vs haloperidol included^8,14-22:

• Study participants who signed informed consent (and were likely less agitated)
• IM haloperidol doses typically >5 mg (eg, 6.5 to 10 mg).

As with studies comparing lorazepam with haloperidol, the results of these RCTs revealed that IM aripiprazole, olanzapine, and ziprasidone were at least as effective as IM haloperidol, with haloperidol having a significantly increased risk of akathisia, dystonia, and other EPS.^8,14-22 The greater EPS risk of haloperidol is not surprising given the use of comparison doses up to 10 mg.

An updated 2017 Cochrane review of haloperidol for psychosis-induced aggression or agitation concluded that⁹:

• haloperidol is an effective intervention, although the evidence is “weak”
• significant treatment effects may take as long as 1 to 2 hours following multiple IM injections
• in contrast to SGAs, treatment with haloperidol carries a significant risk of EPS
• adding a benzodiazepine “does not have strong evidence of benefit and carries risk of additional harm.”

Continue to: Haloperidol's well-known toxicity