The invention describes novel nitrosated and/or nitrosylated H.sub.2 receptor antagonist compounds, and novel compositions comprising at least one H.sub.2 receptor antagonist compound that is optionally substituted with at least one NO and/or NO.sub.2 group, and, optionally, at least one compound that donates, transfers or releases nitric oxide, stimulates endogenous synthesis of nitric oxide, elevates endogenous levels of endothelium-derived relaxing factor or is a substrate for nitric oxide synthase and/or at least one nonsteroidal antiinflammatory drug, antacid, bismuth-containing reagent or anti-viral agent. The invention also describes methods for treating and/or preventing gastrointestinal disorders; improving gastroprotective properties of H.sub.2 receptor antagonists; decreasing the recurrence of ulcers; facilitating ulcer healing; preventing and/or treating inflammations and microbial infections, ophthalmic diseases and disorders, multiple sclerosis, and viral infections; and decreasing or reducing the gastrointestinal toxicity associated with the use of nonsteroidal antiinflammatory compounds.