Droperidol Prolongs QT 30 msec – Does This Matter?

February 9, 2022

Written by Clay Smith

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Low-dose droperidol prolonged the QTc in non-agitated ED patients who were prospectively monitored, but effects were transient and not associated with dysrhythmias.

Why does this matter?
Droperidol is a useful drug in patients with nausea and headache. It is also often used for agitation. It received a black box warning for QT prolongation based on case reports of torsades de pointes (TdP), but the doses used were unusually high (50-100x normal, i.e. up to 600mg!), and the circumstances surrounding this black box warning were a little shady. When a patient is on a cardiac monitor, does droperidol prolong QTc, and if so, how much?

QT increase is real – but is it significant?
This was a prospective trial of 68 non-agitated ED patients – median 42 years old, predominantly with headache, 66% female – who were continuously monitored before and 30 minutes after droperidol was given. The dose was between 0.625 and 2.5 mg (median 1.875 mg). The QTc increased by an average of 30 msec in these patients. Three increased by ≥60 msec; 12 (17.6%) had prolongation ≥500 msec. None died. After a 2-minute bolus dose, the QT peaked at 10 minutes and then returned to normal within about 30 minutes. There were 32 patients (47%) on home meds known to prolong QT, 6 (8.8%) who received QT-prolonging meds in the ED, and 2 (2.9%) with baseline long QT syndrome, all of whom were enrolled in this study and got droperidol. The FDA says, “drugs that prolong the mean QT/QTc interval by >20 ms have a substantially increased likelihood of being proarrhythmic.” However, another study estimated the incidence of TdP after droperidol to be 6 per 100,000. This small study shows us that transient QT prolongation happens with low-dose droperidol, but the clinical significance of this finding is less clear.

Source
Prospective real-time evaluation of the QTc interval variation after low-dose droperidol among emergency department patients. Am J Emerg Med. 2022 Feb;52:212-219. doi: 10.1016/j.ajem.2021.12.039. Epub 2021 Dec 22.