Comparative efficacy of parenteral histamine (H2)-antagonists in acid suppression for the prevention of stress ulceration.

Stress-related mucosal damage is related to a high intraluminal hydrogen ion concentration, a low intramural pH value, and a breakdown of the gastric mucosal barrier. Because the presence of gastric acid is required for stress-related mucosal damage to occur, therapy aimed at increasing intraluminal pH values has often been used as prophylaxis against complications. The amount of acid suppression required for adequate prophylaxis of gastrointestinal bleeding from stress-related mucosal damage has not been determined, but many investigators use a target gastric pH level of 3.5 to 4.0. When intravenous histamine (H2)-receptor antagonists are given in bolus dosing regimens to critically ill patients, fluctuations in gastric pH values are often observed, as might be expected. However, recent studies with primed continuous infusion of cimetidine in critically ill patients have demonstrated that consistent elevation of gastric pH to 4.0 may be attained with this regimen. Studies with continuous infusions of ranitidine are less conclusive; little information is available on famotidine.