Further studies of the anti-recall effect of lorazepam: A dose--time--effect relationship.

The time of onset and duration of the anti-recall action of lorazepam were assessed under clinical conditions by measuring recall and recognition of visual stimuli 24 hours after intravenous administration of lorazepam. The visual stimuli were first presented 5-240 minutes after 2 mg and 5-360 minutes after 4 mg lorazepam. Retrograde amnesia was not produced. Lorazepam, 2 mg, produced a short anti-recall effect (anterograde amnesia) in 50 per cent of the cases, with a latency of 30 minutes and a duration of less than half an hour. Duration and frequency of the anti-recall effect were greater after 4 mg, while the latency was shorter. More than 70 per cent of the individuals tested were amnesic for the visual stimuli 15 minutes to 4 hours after 4 mg lorazepam. Sedation was satisfactory and long-lasting following both doses of lorazepam, but was not related to the anti-recall effect.