Olanzapine and benztropine as a cause of ischemic colitis in a 27-year-old man.

Ischemic colitis is a rare adverse effect of antipsychotic medications and is most commonly associated with the phenothiazine class of antipsychotics and atypical antipsychotics such as clozapine and olanzapine. The risk is further increased when antipsychotics are taken in conjunction with anticholinergics. A 27-year-old man with a history of bipolar disorder and depression presented to the emergency department with 6 days of constipation, abdominal pain, nausea, and nonbloody vomiting. He later developed multiple episodes of hematochezia and fever. Within the preceding 2 weeks, his medication regimen of divalproex sodium, aripiprazole, and trihexyphenidyl, had been changed to olanzapine, benztropine, and bupropion. The patient's physical examination showed diffuse abdominal tenderness, guarding, and distension and laboratory tests revealed a leukocytosis. A computed tomographic scan of the abdomen/pelvis showed colitis extending from the splenic flexure to the sigmoid colon, without evidence of perforation. A colonoscopy revealed severe ischemic colitis involving the descending and sigmoid colon, which was confirmed on biopsy. Given the temporal association between the new medications and onset of symptoms, the patient's ischemic colitis was likely caused by olanzapine or the combination of olanzapine and benztropine, likely secondary to their anticholinergic properties. Thus, providers should take a thorough history and counsel patients regarding the risks of constipation when starting antipsychotic medications, particularly those with anticholinergic activity. Despite the fact that ischemic colitis is such a rare adverse effect of antipsychotic medications, it is important to consider because of its potentially fatal outcomes.