Relative amnesic actions of diazepam, flunitrazepam and lorazepam in man.

1. Ten postcards were shown to groups of ten to twenty patients over 60, 90 or 270 min after intravenous injection of saline, diazepam (10 and 20 mg), flunitrazepam (1 and 2 mg) and lorazepam (4 mg). 2. Incidence of amnesia was estimated by the patients' ability to recall or recognize these cards and to recall various other incidents in the para-anaesthetic period. 3. The use of a dummy confirmed the reliability of the method of testing for amnesia in man. 4. Flunitrazepam produced a dose-related incidence of amnesia slightly longer than with the equivalent (1 x 10) dose of diazepam. 5. The onset of amnesia was slower with lorazepam (4 mg) but appeared to last for up to four hours. 6. This amnesic action of lorazepam was paralleled by a useful sensitive effect but there was no similar correlation for diazepam and flunitrazepam. 7. With three drugs of different duration of action it should be possible to produce amnesia for any required clinical situation.