Anticholinergic poisoning

Page most recently updated 7 September 2026

This page focuses on the reported psychiatric associations, which may be the initial presenting manifestation, and on other clinical features that may assist the psychiatrist or primary care physician in identifying the underlying diagnosis, considered through the lenses of the diagnostic lenses framework.

Anticholinergic poisoning is a toxicologic disorder caused by excessive muscarinic receptor blockade, most often occurring after overdose or accumulation of medications with anticholinergic properties. A distinctive presentation may include the combination of acute neuropsychiatric change, autonomic findings, characteristic pupillary abnormalities, and a relevant medication or toxic exposure.

It can present with psychiatric features such as agitation, anxiety, irritability, behavioural change, perceptual disturbances, hallucinations, and disorganized behaviour. In most cases, prominent psychiatric manifestations occur in the context of an anticholinergic delirium. Rarely, psychotic symptoms have been reported in the absence of overt delirium or significant cognitive impairment.

Other characteristic features include anticholinergic delirium with impaired attention and disorientation, often accompanied by visual hallucinations and picking or other purposeless behaviour. Pupillary dilation with impaired accommodation, blurred vision, and reduced or absent bowel sounds are characteristic. Urinary retention is also an important clinical clue. Severe poisoning may progress to seizures, coma, hyperthermia, rhabdomyolysis, and multiorgan complications.

From a multisystemic lens perspective, clinical features in other body systems include (but are not limited to):

  • Cardiovascular: Tachycardia, hypertension and, in severe poisoning, cardiac conduction abnormalities or ventricular arrhythmias.

  • Gastrointestinal: Dry mouth, reduced bowel sounds, constipation and, in severe cases, ileus.

  • Dermatologic: Dry, flushed skin and reduced sweating, with hyperthermia in more severe poisoning.

Early diagnosis is important because anticholinergic poisoning can progress rapidly to severe hyperthermia, seizures, cardiac arrhythmias, coma, and other life-threatening complications. Prompt recognition allows the offending agent to be discontinued and supportive treatment initiated, with severe cases requiring urgent toxicologic assessment and management.

Selected references and further reading — Multisystemic lens

Cardinal RN, Bullmore ET. The diagnosis of psychosis. Cambridge: Cambridge University Press; 2011.

Sachdev PS, Keshavan MS, editors. Secondary schizophrenia. Cambridge: Cambridge University Press; 2010.

Levenson JL, editor. The American Psychiatric Association Publishing textbook of psychosomatic medicine and consultation-liaison psychiatry. 3rd ed. Washington (DC): American Psychiatric Association Publishing; 2019.

Stern TA, Beach SR, Smith FA, Freudenreich O, Vranceau AM, Fava M, editors. Massachusetts General Hospital handbook of general hospital psychiatry. 8th ed. Philadelphia: Elsevier; 2025.

Arciniegas DB, Yudofsky SC, Hales RE, editors. The American Psychiatric Association Publishing textbook of neuropsychiatry and clinical neurosciences. 6th ed. Washington (DC): American Psychiatric Association Publishing; 2018.

Agrawal N, Faruqui R, Bodani M, editors. Oxford textbook of neuropsychiatry. Oxford: Oxford University Press; 2020.

Boland R, Verduin M, editors. Kaplan and Sadock's comprehensive textbook of psychiatry. 11th ed. Philadelphia: Wolters Kluwer; 2024.

Loscalzo J, Fauci AS, Kasper DL, Hauser SL, Longo DL, Jameson JL, editors. Harrison's principles of internal medicine. 22nd ed. New York: McGraw Hill; 2025.