[Comparison of effects of intravenous versus intramuscular famotidine on pH and volume of gastric juice].

Famotidine, an H2-antagonist, is frequently used for prevention of acid aspiration in surgical patients. Intravenous as well as intramuscular administration of famotidine has proved effective to reduce gastric acid secretion during anesthesia. However, the onset and duration of action of famotidine following intravenous administration has not been extensively investigated. In the present study on 89 patients undergoing elective surgery, the effects of famotidine 20 mg administered intravenously 5-30 min before endotracheal intubation on pH and volume of gastric contents aspirated 0, 1, 2, and 4 hrs after tracheal intubation and immediately after extubation through nasogastric tube were compared with the effects of the drug administered intramuscularly one hour before endotracheal intubation. Famotidine administered intramuscularly 5-14 min before endotracheal intubation produced inadequate suppression of gastric secretion after tracheal intubation. In contrast, intravenous famotidine given 15-30 min before tracheal intubation, as well as the intramuscular administration of famotidine as premedication, effectively decreased gastric fluid volume and increased gastric pH. Suppression of gastric secretion by intravenous and intramuscular famotidine continued for over 4 hours. Intravenous famotidine has a rapid onset and a long duration of depressant action on gastric secretion, thus reducing the risk of aspiration pneumonitis during and after general anesthesia.