An 88-year-old white woman with osteoarthritis has noticed mild epigastric discomfort for several weeks. Naproxen has helped her joint symptoms. She has emesis that resembles coffee grounds on three occasions.Select the most likely cause of gastrointestinal blood loss

This patients have acute upper gastrointestinal bleeding, which is often characterized by emesis that looks like red blood or coffee grounds. Nonsteroidal anti-inflammatory drugs (NSAIDs), even over-the-counter brands, are common causes of GI bleeding. Preceding symptoms may be mild before the bleeding occurs. Cotreatment with misoprostol decreases GI bleeding but is expensive. Selective COX-2 inhibitors decrease the incidence of GI bleeding but have been shown to increase cardiovascular events and to carry the same risk of renal dysfunction, edema, and blood pressure elevation as nonselective NSAIDs.