A further examination of the time-dependent effects of oxazepam and lorazepam on implicit and explicit memory

Until recently, research indicated that all benzodiazepines impair explicit memory, while only lorazepam impairs priming. Stewart and associates provided preliminary data which indicated that both oxazepam and lorazepam may impair implicit memory: but in a time-dependent fashion. The present study was designed to replicate Stewart et al.'s findings after overcoming several limitations of the original study. Thirty subjects were administered an acute dose of lorazepam (2 mg), oxazepam (30 mg) or a placebo and were tested with an implicit (word-stem completion) test and an explicit (cued recall) test. However, subjects were only tested at 170 min postdrug (close to oxazepam's theoretical peak concentration) to rule out the possible "explicit memory contamination" explanation of the Stewart et al. implicit memory findings. Consistent with previous research, both drugs impaired explicit memory relative to placebo. Also, both lorazepam and oxazepam impaired priming performance, supporting the "time-dependence" interpretation of the Stewart et al. findings. The results also indicate that episodic memory is impaired by both benzodiazepines in a lime-dependent fashion even when the research methodology used involves everyday memory demands.