Respiratory depression droperidol + fentanyl

Biphasic respiratory depression after fentanyl-droperidol or fentanyl alone used to supplement nitrous oxide anaesthesia. Anesthesiology, 44, 291. 

The effect of metoclopramide on oral morphine absorption is an established interaction that can be usefully exploited in anaesthetic practice, but the increased sedation may also represent a problem if the morphine is being given long-term. The morphine-sparing effect of droperidol is also a useful interaction, but the increased sedation and possible respiratory depression and hypotension should be borne in mind. One manufacturer of fentanyl specifically warns that concurrent use with droperidol can result in a higher incidence of hypotension. ... 

Both fentanyl and Innovar depressed the slope of the rebreathing carbon dioxide response curve to 42% 6 of the values obtained in the same subjects when awake. After the last injection of fentanyl or the fentanyl/droperidol combination the slope of the curve increased to 77% 8 of the control level but after reaching a normal level the respiratory depression recurred, the slope of the curve falling to 55% + 5 of the control value. Subsequently the slope of the curve returned to near normal levels. 

The biphasic change in the degree of respiratory depression occurred in 26 of the 29 subjects studied, irrespective of the drugs given. However, full recovery of respiratory function appeared to be quicker after fentanyl with droperidol than after droperidol alone. The authors conclude that droperidol... 

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