192. Alprazolam and lorazepam: Memory impairment on successive learning trials

We havepn%ouslyreportedthatacutehighandlowdosesof alprazohrm (ALP,0.25mg,0.5mg)and lorazepam(LOR,0.5mg, lmg), whichare thoughtobeequivalent inanxiolyticeffects, impairedmemoryperformance ona verballist learningtask(Buschke’sSeIectiveRemindingTask).These findings,however,werebasedon thecumulativerecallof 7 learning trials (totalmall). In the presentanalysis,we examinedthe acuteand chronic effects of these drugs on recall across the 7 trials. Acute effects were examinedbothbeforeandafterchronicb.i.d.treatmentin a doubleblind placebo-control, parallelstudyinhealthyelderly.Initialacutechallengewith singlehighdosesofbothdrugsresultedinsi@lcantdmg x trialinteractions in whichthe dreg-inducedimpairmentsbecamegreateroverthe courseof successivetrialsat i and 2.5 hourspost-drug. No sigMcant drugx kid interactionswerefoundduringchronictreatment.Afterchronictreatment, only acute techallengewith the single high dose of LOR resultedin increasedimpairment acrossthe7 trialsrelativetoplaceboat2.5hours(drug x trkdinteraction). RerhalIengewiththehighdoseofALPno longercaused such increasedimpairment.This suggeststhat toleranceto the adverse effectsof acuterechallengeon recallacrossthe 7 trialsis momlikelyto developas a resultof chronictreatmentwiththe highdoseof ALP.Low dosesof thetwodrugsproducednosignificant drngxtrialinteractions either in theinitialacutechallengeorrechailengeinspiteofsigMcant impairment in totrdredl.