This study was carried out to assess the efficacy of intravenous (IV) famotidine in suppressing gastric secretion over a 48-hour period. Twenty postoperative patients requiring a nasogastric tube received famotidine 20 mg IV every 12 hours and gastric pH was measured continuously by means of an indwelling probe. A baseline recording was performed over the first 4 hours and then the drug was infused every 12 hours (q12h) over a 15-minute period for the subsequent 48 hours. The mean pH value achieved during each time segment under active treatment was significantly higher (P < .001) than the mean basal value. Also the density distributions of minutes spent at the various pH units confirm that famotidine is highly effective (P < .001) in raising and maintaining gastric pH above 4.0 units during most of the drug-related period (44 hours). It can be concluded that repeated intravenous boli of famotidine 20 mg every 12 hours allow us to obtain an effective control of intragastric acidity. The antisecretory action is consistent over the total 48-hour period examined and therefore the use of intermittent infusion of famotidine seems to be advisable, as opposed to the recommended continuous IV administration of cimetidine and ranitidine. There is, however, a considerable intersubject variability in the antisecretory response to the drug.