Restlessness often complicates ERCP and may be a reason for premature termination of the procedure. Our purpose was to evaluate whether a premedication with orally administered lorazepam could reduce the need for sedatives and improve sedation quality. Randomized double-blind trial. Therapeutic ERCP with an intravenous sedation containing midazolam, propofol, and S(+)-ketamine. 95 inpatients (aged 20-91 years). 1 mg of lorazepam (n=47) or placebo (n=48) given orally before ERCP. Total amount of administered propofol. Heart rate, blood pressure, number of oxygen desaturations, and states of restlessness did not differ between the groups. The same amount of midazolam was administered in both groups. There was no significant difference in the total amount of propofol to achieve adequate sedation (lorazepam vs placebo: 71+/-5 vs 63+/-4 microg/kg/min, mean+/-SE). Paradoxically, patients pretreated with lorazepam even needed more propofol in the early phase of sedation (275+/-39 vs 159+/-37 microg/kg in minutes 5-10, P<.05) and the total amount of ketamine administered was higher in this group as well (15.8+/-1.4 vs 11.3+/-1.2 microg/kg/min, P<.05). In both groups there were high rates of satisfaction with the course of the procedure evaluated both by the endoscopists and the patients. The trial failed to show an advantage of an oral premedication with lorazepam. The amount of sedatives administered in the lorazepam group even tended to be higher. A premedication with lorazepam may be counterproductive when followed by sedation containing another benzodiazepine.