GASTROPROTECTANTS: STRATEGIES FOR USING THEM WINN FELINE FOUNDATION SUCCESSFULLY Katie Tolbert, DVM, PhD, DACVIM Gastrointestinal (GI) mucosal protectants including acid suppressants, antacids, misoprostol, and coating agents (sucralfate, barium) are commonly used for the prevention and treatment of gastritis and ulcerative disease in dogs and cats. However, results of veterinary studies investigating these drugs are heterogeneous with some studies failing to demonstrate a benefit. Inappropriate dosing and misuse of these medications for diseases in which they have not proven to be beneficial are likely to blame. Recently published dosing recommendations and suggested indications for use of GI mucosal protectants are likely to improve the outcome of dogs and cats with and at risk for erosive and ulcerative disease. Evidence and indications for the use of acid suppressants can be found as a separate proceedings. Coating agents Sucralfate is a polyaluminum sucrose sulfate that is activated in the acidic environment of the stomach. Its primary mechanism of action is to coat injured and denuded gastroesophageal mucosal epithelium. Other proposed mechanisms of action include prostaglandin stimulation and inhibition of substances that could be injurious to the subepithelium including pepsin and bile acids. Very few studies have evaluated the efficacy of sucralfate for treatment of mucosal injury. In one of the only available studies, sucralfate was not effective in treatment of GI bleeding in dogs undergoing spinal surgery and receiving high dose steroids.1 However, sucralfate is relatively benign with few side effects aside from constipation and potential drug interactions, thus many clinicians including myself administer the medication to dogs and cats with or at-risk for gastric bleeding. More studies are needed to determine if this practice is beneficial for dogs and cats. Sucralfate is available in both tablet and suspension form. Drug interaction studies suggest that sucralfate is not as effective when administered as a tablet.2 Therefore, prior to administration, the tablets should be crushed and mixed with water to create an oral slurry. The aluminum component of the sucralfate suspension can interfere with the absorption of other drugs including tetracyclines and fluoroquinolones. Thus, sucralfate administration should be delayed by at least 2 hours prior to administration of these drugs.2 Since activation of sucralfate is dependent on an acidic pH, drugs that increase gastric pH (e.g., antacids, acid suppressants) should be delayed for at least 1 hr following sucralfate administration. Barium is speculated to have mucoprotective and pro-coagulant effects. It has been reported to have hemostatic effects for a variety of causes of gastrointestinal bleeding in humans.3 To my knowledge, it has not been studied in companion animals but is used frequently in clinical practice. I do not use it in my practice but know many veterinarians who like to use it in combination with acid suppressants for patients who have severe gastric bleeding and can tolerate oral medications. Endoscopy should be delayed at least 24 hours following administration of barium as barium can hinder visualization of the gastrointestinal mucosa and can obstruct the endoscope instrument channel if aspirated. Barium should not be used if gastrointestinal perforation is suspected.4 Antacids Antacids (e.g., calcium carbonate, aluminum hydroxide, magnesium hydroxide) are often incorrectly referred to as acid suppressants. Unlike acid suppressants, which target the production of gastric acid by the parietal cell, antacids are acid-neutralizing drugs and have no effect on the parietal cell proton pump. Therefore, antacids have to be administered more frequently to avoid rebound gastric acid secretion. For this reason, effective administration of antacids can be problematic in vomiting or anorectic patients. Other proposed mechanisms of action of antacids include decreased pepsin activation as a result of increased gastric pH, stimulation of bicarbonate secretion, and formation of complexes with refluxed bile salts. Other common adverse effects of antacids include undesired drug interactions (as mentioned for sucralfate), constipation (aluminum preparations), and diarrhea (magnesium preparations). Similar to the coating agents, antacids are a vastly understudied class of drugs in veterinary medicine. Because of their requirement for frequent administration and the perceived superiority of acid suppressants, I rarely use antacids for gastric bleeding. Acid Suppressants Gastric parietal cells are responsible for the production and secretion of gastric acid. Parietal cells are stimulated by neural and hormonal inputs. Acid suppressant drugs act to block acid production either at the receptors for these inputs or directly at the parietal cell proton pumps. Acid suppressants are more effective and have a longer duration