EFFECTS OF OXAZEPAM AND LORAZEPAM ON IMPLICIT AND EXPLICIT MEMORY - EVIDENCE FOR POSSIBLE INFLUENCES OF TIME-COURSE

The effects of oxazepam (30 mg), lorazepam (2 mg), and placebo on impl icit and explicit memory were studied in two testing cycles, 100 and 1 70 min after drug administration. Thirty healthy volunteers were rando mly assigned to one of three groups (placebo, oxazepam, or lorazepam) in a double-blind, independent groups design. Drug groups were equival ent prior to drug administration on a variety of cognitive measures. F ollowing drug administration, both oxazepam and lorazepam equally impa ired performance on a cued-recall explicit memory task relative to pla cebo, at both testing cycles. Relative to placebo, lorazepam markedly impaired priming on a word-stem completion implicit memory task, at bo th testing cycles. Consistent with previous work, oxazepam failed to p roduce impairments in priming on the word-stem completion task at 100 min post-drug administration. However, oxazepam was found significantl y to impair priming on this latter task relative to placebo, at close to theoretical peak plasma concentration(i.e., 170 min post-drug admin istration). Explanations for the observed detrimental effect of oxazep am on implicit memory task performance are considered, including: poss ible time-dependent effects related to the relative rate of absorption of these two benzodiazepines (BZs); and potential contamination of th e implicit memory task by explicit memory strategies during the second testing cycle.