Alprazolam and lorazepam effects on memory acquisition and retrieval processes.

A double-blind study involving healthy young adult males examined acute effects of two benzodiazepines (alprazolam 1 mg and lorazepam 2 mg) on long-term memory acquisition and retrieval, using Buschke's "selective reminding" task and a free recall task. Subjects learned lists consisting of high and low imagery nouns. The assessments, done at baseline and hourly for 4 hours after drug ingestion, also included two psychomotor tests and subjective ratings by subjects. Both benzodiazepines produced marked memory impairment. Contrary to the prevailing view that benzodiazepines primarily impair long-term memory acquisition rather than retrieval, results from Buschke's task indicated impairment of retrieval as well. This finding may be related to the procedures and assumptions of Buschke's task. The benzodiazepine-induced impairments increased over the course of successive trials on the same list. Both drugs decreased the normal superiority in recall of high imagery words relative to low imagery words, impaired psychomotor performance, and increased subjective sedation. Alprazolam and lorazepam produced equally intense impairments. Alprazolam tended to produce earlier impairment and earlier recovery.