BACKGROUND
Cholinergic crisis is a life-threatening condition caused by excessive cholinergic stimulation. Distigmine, a cholinesterase inhibitor, and bethanechol, a cholinergic agonist, are both used to treat neurogenic bladder and are occasionally prescribed together. Although both agents can cause cholinergic toxicity, it remains unclear whether clinical conditions such as severe constipation may contribute to severe cholinergic crisis.
CASE REPORT
An 84-year-old man with chronic constipation was transported to the emergency department because of impaired consciousness. Distigmine (5 mg/day) had been started 3 months before admission, and bethanechol (45 mg/day) had been added approximately 1 month before admission. On arrival, the patient was comatose with severe bradycardia, shock, respiratory failure, and prominent cholinergic manifestations. Laboratory test results showed renal dysfunction and markedly reduced serum butyrylcholinesterase activity. Abdominal computed tomography demonstrated severe fecal retention extending from the descending colon to the rectum. Based on the characteristic cholinergic manifestations, medication history, and low serum butyrylcholinesterase activity, cholinergic crisis induced by combined distigmine and bethanechol therapy was diagnosed. The patient required intensive care, including mechanical ventilation, norepinephrine and vasopressin infusions, and continuous atropine administration. His condition gradually improved and he was discharged on day 77.
CONCLUSIONS
Severe constipation may represent an additional contributor to cholinergic toxicity in older adults receiving combined cholinergic therapy for neurogenic bladder. Although causality cannot be established in a single case, careful assessment of bowel status and other risk factors is warranted when prescribing cholinergic agents.

Keywords: Cholinergic Agents; Cholinesterase Inhibitors; Constipation; Poisoning