Which medication is commonly associated with gastrointestinal bleeding when used chronically?

Chronic use of NSAIDs (non-steroidal anti-inflammatory drugs) is well-documented to be associated with gastrointestinal bleeding. NSAIDs work by inhibiting cyclooxygenase enzymes (COX-1 and COX-2), which leads to a reduction in the production of prostaglandins. Prostaglandins play a crucial role in maintaining the protective mucous layer of the gastrointestinal tract. When NSAIDs are used over a long period, the decreased prostaglandin synthesis can result in erosion of the gastric mucosa, increasing the risk for ulcers and gastrointestinal bleeding.

In contrast, other medications such as allopurinol, phenazopyridine, and ACE inhibitors do not have the same level of association with gastrointestinal bleeding when used chronically. Allopurinol is primarily used to manage gout and does not typically affect the gastrointestinal mucosa significantly. Phenazopyridine is used to relieve urinary tract symptoms and does not have a known impact on gastrointestinal bleeding. ACE inhibitors, which are used in managing hypertension and heart failure, also do not directly cause gastrointestinal bleeding as a common side effect. Thus, NSAIDs remain the primary concern for gastrointestinal complications when used long-term.