OBJECTIVE: To report a case of acute self-limiting ischemic colitis in a patient who was self-medicating with a proprietary over-the-counter oral decongestant containing pseudoephedrine. CASE SUMMARY: A 46-year-old white man developed clinical, endoscopic, and histologic features of acute ischemic colitis after taking a proprietary oral decongestant containing pseudoephedrine 240 mg/day for one week. The total daily dose was at the upper limit of recommended doses for pseudoephedrine (as a single drug or in combination products). The patient was also taking tramadol 150 mg/day for chronic back pain. He made a complete recovery. There were no other explanations for the episode of ischemic colitis. DISCUSSION: An objective causality assessment based on the Naranjo probability scale revealed pseudoephedrine to be a probable cause of ischemic colitis in our patient. Pseudoephedrine occasionally causes vascular insufficiency due to intense vasoconstriction, even at standard doses. Although our patient was not taking an excessive dose of pseudoephedrine, it is possible that the concurrent use of pseudoephedrine and tramadol may have increased adrenergic vasoconstriction, predisposing to ischemic colitis. CONCLUSIONS: Prolonged or intensive use of medications containing pseudoephedrine should be avoided, and the package information should contain advice that the medication should be ceased if abdominal pain or other ischemic symptoms occur.