The effect of diazepam and fentanyl on mental, psychomotor and electroencephalographic functions and their rate of recovery.

Ten healthy male subjects received diazepam (10 or 20 mg), fentanyl (0.1 or 0.2 mg) or a placebo intravenously at weekly intervals according to a latin square design. They were tested on a battery of psychological and electroencephalographic tests at 0.5, 2, 6, and 8 hrs following injection. Fentanyl had little effect on memory while diazepam reduced the ability to learn without increasing forgetting of material alread acquired. By the 2nd hour post injection, only the low dose of fentanyl had no residual effect. Recovery was complete by the 6th hour for all treatments according to the psychological tests except for the lagging effect of high dose of diazepam on memory. The electroencephalographic effects of diazepam persisted beyond the end of the testing sessions while those of the high dose of fentanyl recovered by the 8th hour. Thus in the dosages tested, diazepam had more intense and prolonged effects than fentanyl.