Overview of pharmacologic agents for acid suppression in critically ill patients

Purpose. The physiology of acid secretion, rationale and goals for acid suppression in critically ill patients, and mechanism of action, pharmacokinetics, pharmacodynamics, and safety of histamine H ₂-receptor antagonists (H₂RAs) and proton pump inhibitors (PPIs) are discussed. Summary. Acid-suppressant therapy may be used in critically III patients to prevent stress-related mucosal disease or the recurrence of peptic ulcer bleeding. The intragastric pH goal is 3.5-4.5 and 6 or higher, respectively. H₂RAs block only one of three pathways in acid secretion and provide less potent acid suppression than PPIs, which block the final common pathway in acid secretion. In addition, tolerance that occurs with H₂RAs does not occur with PPIs. All PPIs work in a similar manner, but differences exist in the pharmacokinetic profiles and binding to the proton pump; the clinical relevance of these differences remains debated. The safety profiles of H₂RAs and PPIs are similar; however, the H ₂RA dose, but not the PPI dose, must be adjusted for patients with renal dysfunction. The risk of drug interactions mediated by cytochrome P-450 enzymes is lower with PPIs than with cimetidine, an H₂RA. Several new PPI dosage forms have been introduced, facilitating drug administration in the critical care setting. Conclusion. Both H₂RAs and PPIs are safe agents to use for providing acid suppression in critically ill patients, but PPIs offer several potential advantages over H₂RAs.