Lorazepam. a new benzodiazepine. was compared with a standard surgical premedicant. pentobarbital. In a double-blind study in 128 patients. lorazepam. 2 and 4 mg. and pentobarbital. 50 and 100 mg. were given intravenously in a randomized sequence. Significant differences were noted; lorazepam was found to provide greater sedation. lack of recall, and greater antianxiety effect than pentobarbital. No significant adverse effects were noted following either drug. Vital signs remained stable.