Although cimetidine is more effective than a placebo for the prophylaxis of stress-induced ulcers, it has no advantage over titrated antacid dosing. Several comparative studies even suggest that combining cimetidine with antacid is no more effective than use of full-dose antacid. Therefore, we recommend prophylatic use of cimetidine' only when very large dosages of antacid are required, in order to minimize acid-base disturbances.