Effectiveness of Haldol As an Emergency Tranquilizer

In psychiatric emergency settings, the standard treatment for aggressive or agitated behavior during psychosis is an injection of Haldol (haloperidol). A dosage of 5 to 10 mg is typically effective at putting a restless patient to sleep in a relatively short period. Aggressive patients are worrisome because they can do harm to themselves or others. An agitated person in the middle of a psychotic episode is not going to respond to the ordinary line of treatments. In some emergency settings, attending physicians choose to combine Haldol with a strong antihistamine such as Phenergan (promethazine). This practice is not recommended by international guidelines; however, researchers believed that the practical experience of emergency room doctors might have revealed a better, safer treatment option for agitated patients.

A group of international researchers conducted a study at a Brazilian hospital comparing the effectiveness of certain approaches to managing aggression and restlessness in patients admitted to a psychiatric emergency room. When an admitted patient qualified for participation in the study, they were randomly administered either Haldol alone or Haldol in tandem with Phenergan. A total of 316 people participated before the trial was stopped. One-hundred and sixty received the combination treatment, while the other 156 received only Haldol. Doctors and nurses observed and recorded how much time passed between administration of drugs and sedation, as well as any adverse side effects.

The trial ended early because data monitors quickly saw the results. Haldol by itself is neither as safe nor effective as when used together with an antihistamine like Phenergan. First, full sedation took much longer with Haldol alone. The longer patients remain agitated, the greater the danger they represent. In addition, one of the more troubling side effects of Haldol is dystonia—painful spasms of large muscle groups. Antihistamines seem to counter this effect, although the exact mechanism isn’t well understood. Because of these dangers, the study was halted when only halfway complete.

Despite the fact that the Brazilian study was left unfinished, the results are still significant. The researchers strongly recommend that psychiatric emergency wards institute administration of Haldol plus Phenergan as standard procedure for aggressive patients. This combination helps increase the safety of both patients and those charged with caring for them.


  1. PubMed Health [Internet]. (n.d.). Bethesda (MD): National Library of Medicine. Haloperidol. Retrieved February 29, 2012. Available from: http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0000604/
  2. Huf, G., Coutinho, E., Adams, C. (2007). Rapid tranquillisation in psychiatric emergency settings in Brazil: pragmatic randomised controlled trial of intramuscular haloperidol versus intramuscular haloperidol plus promethazine. BMJ. 335(7625):869. Published online 2007 October 22. doi: 10.1136/bmj.39339.448819.AE


© Copyright 2011 by James Pendleton. All Rights Reserved. Permission to publish granted to GoodTherapy.org.

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