Background: Ischemic colitis (IC) is an uncommon adverse event associated with antipsychotic agents, more commonly found with phenothiazine drugs and atypical neuroleptics such as clozapine. The risk of developing ischemic colitis increases when anticholinergic drugs are associated.Case report: We report the case of a 38-year-old woman with a history of schizoaffective disorder who had been on chronic quetiapine for 3 years, and presented to the ER because of diarrhea for 5 days. Four months previously, olanzapine had been added to her psychiatric drug regimen. Physical examination revealed abdominal distension with abdominal tympanic sounds and tenderness. Emergency laboratory tests were notable for increased acute phase reagents. Tomography revealed a concentric thickening of the colonic wall in the transverse, descending and sigmoid segments, with no signs of intestinal perforation. Colonoscopy demonstrated severe mucosal involvement from the sigmoid to the hepatic flexure, with ulcerations and fibrinoid exudate. Biopsies confirmed the diagnosis of ischemic colitis. The only relevant finding in her history was the newly added drug to her baseline regimen. An adverse effect was suspected because of its anticholinergic action at the intestinal level, and the drug was withdrawn. After 6 months of follow-up clinical, laboratory and endoscopic recovery was achieved.Discussion: Antipsychotic medication should be considered as a potential cause of ischemic colitis, particularly atypical antipsychotics such as clozapine and olanzapine; despite being uncommon, this adverse event may result in high morbidity and mortality.Key words: Ischemic colitis. Olanzapine. Antipsychotic drugs. INTRODUCTIONIschemic colitis (IC) is the most common cause of intestinal ischemia, and represents around 50% of cases. It results from transient vascular flow deprivation in the colon (1,2). Most cases resolve spontaneously, but others progress to more severe presentations that require surgical management (2). Incidence rates vary with age, and oscillate from 1.1 per 100,000 inhabitant-years among patients younger than 40 years to 107 per 100,000 inhabitant-years among those at or above 80 years of age. It typically involves elderly patients with multiple comorbidities, and is associated with high in-hospital mortality (11.5%) and surgery (17%) rates (3). In clinical practice many cases are overlooked because of mild or transient presentations with no clear trigger.Several drugs have been associated with the development of intestinal ischemia, including digitalis, diuretics, estrogens, antibiotics, and non-steroidal anti-inflammatory drugs (4). IC is an uncommon adverse event of antipsychotic drugs, particularly phenothiazines and atypical or second-generation compounds (5). The effect of these drugs is enhanced when anticholinergics are associated. Clozapine is the atypical antipsychotic most commonly described in the literature as a cause of IC (6). In contrast, the IC risk associated with quetiapine is lower given its milder anti...

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