The effects of a single oral dose of lorazepam and alprazolam on reaction times in young healthy volunteers.

Lorazepam (Temesta) and alprazolam (Xanax) are two benzodiazepines which are widely used for their anxiolytic activity. In this study their effect on psychomotor functions was investigated. Eight young healthy volunteers participated in the experiments. Using a double-blind cross-over design, the effect of single oral doses of lorazepam (2.5 mg) and alprazolam (0.5 mg) on a choice reaction time test to visual stimuli (letter pairs presented on a computer screen), were assessed. The experimental procedure consisted of three sessions which differed from each other either by the stimulus presentation rate, or by the presence or absence of a warning signal. In all three sessions, lorazepam, when compared with placebo, significantly prolonged the reaction times (RT), while alprazolam did not. Increasing the interstimulus interval resulted in an equal increase of the reaction times in the three conditions. On the other hand, the introduction of a warning signal which preceded the presentation of the letter pairs, improved performance in the three conditions. This improvement was more pronounced after lorazepam than after placebo. This finding is interpreted as a partial recuperative effect for the impaired performance in the baseline condition after intake of lorazepam.