[The effect of the morphine antagonist naloxone on the effect of fentanyl].

1. In healthy volunteers fentanyl (0.15 mg i.v.) induces a reduction of awareness and vigilance and in some persons a transition to sleepiness or sleep stages. The course of these changes with time can be shown in narcograms, consisting of vigilance indices which correspond to the different EEG-stages. 2. Naloxon (0.4--1.6 mg i.v.) reduces the hypnotic effect of fentanyl or antagonizes it completely. 3. Index values of rapid eye movements in wakefulness measured oculographically indicate a reduction of motor activity after administration of fentanyl, when stages of reduced vigilance appear. Injections of naloxone following later on diminish this effect of fentanyl or antagonize it completely, not so does levallorphan.