A dosage alternative for H2-receptor antagonists--constant infusion.

Control of gastric acid is accomplished either by buffering it with antacids or by preventing acid secretion with H2-receptor antagonists. Advantages of antacids are their rapid onset of action and the possibility of precisely titrating intragastric pH. In practice, however, they are cumbersome to use because they must be administered frequently (often hourly) and thus require excessive nursing time. In addition, their use often leads to undesirable side effects, such as diarrhea. Cimetidine and ranitidine are H2-receptor antagonists that differ primarily in their potency, ranitidine being four to ten times more potent than cimetidine. With either drug, the patient's intragastric pH falls below 5 by about the fourth hour after the dose. One way to avoid the peaks and valleys of acid secretory control is to use constant infusion. Infusion rates of 50 mg/hr of cimetidine preceded by loading doses of 300 mg of cimetidine often produce a constant intragastric pH above 5. It is essential that intragastric above 5. It is essential that intragastric pH be checked and infusion rates increased or antacids added if pH drops below 5. Bauer used constant infusion of cimetidine in patients with upper gastrointestinal bleeding. He found constant infusion more successful, but his end-point was merely to stabilize the patient before surgery. At UC Davis, we compared constant infusion with intermittent dosing (300 mg of cimetidine every six hours) in patients admitted to the intensive care unit with upper gastrointestinal bleeding.