Phentermine Induced Ischemic Colitis

Abstract

Purpose: Introduction: Weight loss medications have historically been cautiously supported due to adverse side effects such as pulmonary hypertension and valvular heart disease. In 1997 the FDA withdrew the combination of fenfluramine and dexfenfluramine from the market due to these adverse events. Phentermine, a commonly prescribed medication for short-term weight loss, works as a sympathomimetic and is an amphetamine derivative that remains available for prescription. We report a unique case of severe ischemic colitis following the use of phentermine in a patient with no other risk factors for ischemia. Case Presentation: A 57 year old female GI nurse presented to the emergency room complaining of bilateral lower quadrant abdominal pain followed by hematochezia two hours later. Digital rectal exam in the ER revealed bright red blood. Past medical history was unremarkable for any risk factors for gastrointestinal ischemia aside from well-controlled hypertension on a single antihypertensive. Phentermine had been prescribed five months prior at a dose of 30mg daily for weight loss. A colonoscopy was performed and showed diffuse contiguous erythema, superficial ulceration, and edema from the mid sigmoid colon to the mid transverse colon. A strictured area was also appreciated in the descending colon. The rectal and proximal colonic mucosa were normal. Biopsies obtained showed patchy mucosal hemorrhage and necrosis and confirmed the diagnosis of ischemic colitis. Phentermine had been held on admission and all symptoms resolved within 48 hours with supportive care. Two months later the patient remains asymptomatic and has not resumed her weight loss supplement. Discussion: There is one case report of ischemic colitis following fenfluramine in combination with dexfenfluramine. There is, however, only one published case report of phentermine in association with ischemic colitis that only involved a small segment at the splenic flexure. Gastrointestinal bleeding is not listed as a possible side effect of this commonly prescribed medication. Phentermine has been associated with ischemic neurologic events such as transient ischemic attacks and cerebral infarcts and could, through similar physiology, cause gastrointestinal ischemia. This unique case describes an instance of severe ischemic colitis following the use of phentermine involving almost the entire left colon and highlights the need for heightened awareness to identify patients and inform providers of the risk of gastrointestinal ischemia from this medication.