Effect of oral benzodiazepines on memory

The effects of the oral administration of diazepam 5, 10 and 20 mg, flunitrazepam 0.5 and 1 mg and lorazepam 1, 2 and 4 mg on memory were studied in groups of healthy patients before surgery. The degree of sedation was noted also. A dose-related amnesic effect was produced by all the drugs, but this was not significant with diazepam 5 mg and lorazepam 1 mg. Larger doses of diazepam (10 and 20 mg) produced brief amnesia comparable to equivalent doses of flunitrazepam (0.5 and 1 mg). There was the same delay in the onset of amnesia after oral lorazepam 4 mg as when it was given i.v. and its effect lasted for at least 90 min after administration. In contrast to the effect of the same drugs given i.v., drowsiness and failure of recognition follow a similar time course.