The mucosal barrier is the name given to the barrier in the stomach that resists the back-diffusion of hydrogen ions. The barrier is a layer of thick mucus secreted together with an alkaline fluid. Since the mucus is a gel, it entraps the alkaline fluid so that the stomach is coated.
Sucralfate, a polymer of sucrose with aluminum hydroxide, forms a protective coating on the mucosal lining, particularly in ulcerated areas. In the presence of acid, it becomes a gel that adheres to epithelial cells and ulcer craters. Sucralfate is only minimally absorbed and can cause constipation.
Misoprostal is a prostaglandin analog that increases release of bicarbonate and mucin (a component of mucus) and reduces acid secretion by binding to prostaglandin receptors on parietal cells. Because NSAIDs (nonsteroidal anti-inflammatory drugs) inhibit prostaglandin formation, a synthetic prostaglandin such as misoprostal is sometimes given to reduce NSAID-induced damage.