Parenteral premedication with lorazepam--a dose/response study.

The dose/response characteristics of lorazepam when administered parenterally as a premedicant drug were studied. The parameters studied included its' sedative and amnesic effects as well as effects on the cardiovascular and respiratory systems. Intramuscular and intravenous routes using doses 2 mg, 3 mg and 4 mg were compared. The findings suggest that lorazepam's sedative and amnesic effects were more pronounced with the intravenous route, and that in both routes the incidence and degree of sedation and of amnesia were dose dependant. There were minimal changes in arterial blood pressure, pulse rate or quality of respiration. We recommend that due to local logistic factors, the intravenous route might be more suitable, affording a more rapid onset of sedation before induction of anaesthesia, provided that close nursing observation is available. Furthermore, lorazepam 2 mg intravenously is just as effective as the larger doses with less incidence of nausea and vomiting associated with the larger doses.