Thursday 1 July 2021

A double blind RCT of IV chlorpromazine vs prochlorperazine for the treatment of acute migraine in the ED

This single centre study out of the ED at Austin Health, enrolled patients with migraine to either IV chlorpromazine (Largactil/Thorazine) vs 12.5mg IV prochorperazine (Stemetil/Compazine).

The primary outcome was a reduction in pain at 60 minutes as reported on a 11 point (0-10) Numerical Rating Scale (NRS). They also recorded some secondary outcomes and safety measures.


65 patients were included.

It doesn't take a statistical genius to understand this study was only powered to find a large treatment difference. So, it is no surprise they didn’t find one in the primary nor secondary outcomes.

The only statistical difference noted was side effects. Chlorpromazine had worse hypotension and syncope.

What does this study add to our knowledge?

Not much.

It was an elegant study design but woefully underpowered to adequately answer the study question. It makes me wonder why they bothered. Such small numbers can only find huge differences (which rarely exist in medicine) and often cannot get rid of baseline difference in study population and confounding; precisely the reason for conducting a randomized trial.


Hodgson SE, Harding AM, Bourke EM, et al. A prospective, randomized, double-blind trial of intravenous chlorpromazine for the treatment of acute migraine in adults presenting to the emergency department. Headache. 2021;61:603-11. [link to article]

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