Efficacy of lorazepam and lormetazepam as intravenous premedicants for anesthesia and surgery.

Lorazepam 4 mg and lormetazepam 2 mg were compared as intravenous premedicants by assessing their effects on the level of consciousness and anxiety, sensory and motor functions, neuromuscular function and vital parameters in sixty surgical patients in a randomized study. Lormetazepam exerted a marked sedative-hypnotic effect maximal at 10 min. Lorazepam had a slower onset of action with a peak effect at 40 min on the different neurobehavioral functions but seemed to induce a longer duration of sedation and a more consistently obtunded awareness of perisurgical events than lormetazepam. Sensory functions were similarly affected by both drugs. Motor function was significantly more impaired by lormetazepam than by lorazepam (P 0.05). Both drugs significantly decreased anxiety for at least 60 min after premedication. Important changes of muscle tone were noticed with lormetazepam at 10 to 30 min resulting in upper airway obstruction in some patients. All hemodynamic changes remained clinically acceptable in both groups and no side effects were seen. The clinical anesthesiologists rated the quality of premedication as unsatisfactory in 7% of the patients treated with lorazepam and in 27% of those receiving lormetazepam. Together with its milder neurobehavioral effects and highly effective anxiolytic action, these factors favor the use of lorazepam for anesthetic premedication despite a relatively slow onset of action.