The effects of cimetidine and ranitidine with and without metoclopramide on gastric volume and pH in morbidly obese patients.

The efficacy of preanaesthetic intravenous cimetidine versus ranitidine with and without metoclopramide for acid aspiration prophylaxis was assessed in 60 morbidly obese patients in a double-blind manner. Group 1 patients received cimetidine 300 mg + saline. Group 2 patients received cimetidine 300 mg + metoclopramide 10 mg. Group 3 patients received ranitidine 100 mg + saline. Group 4 patients received ranitidine 100 mg + metoclopramide 10 mg. Gastric fluid was aspirated for analysis of volume and pH following induction of anaesthesia. All four premedication regimens were equally effective in reducing the gastric volume and acidity and the inclusion of metoclopramide had no additive effect. Although statistically not significant, two patients in the cimetidine groups remained at risk (volume greater than 25 ml and pH less than 2.5) while no patients in the ranitidine groups remained so.