Anticholinergic Toxicity Clinical Presentation

Updated: Feb 23, 2022
  • Author: Mityanand Ramnarine, MD, FACEP; Chief Editor: David Vearrier, MD, MPH  more...
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For all patients with suspected poisoning, determine the precise substance(s) ingested, time of ingestion, quantity ingested, rationale for ingestion, and co-ingestants. Ascertain patient compliance, medical history, prescription medications, and nonprescription medications (including natural or herbal products).

Many medications have anticholinergic properties, which can result in additive toxicity. Always inquire about use of dermally applied drugs (ie, scopolamine transdermal delivery system).

In a study that included 30 patients with chronic pain and 30 control patients, the pain patients were at higher cognitive risk from anticholinergic burden, especially those aged 30 to 39 years. The average number of medications used by patients in the chronic pain group was 3.93, compared with 1.20 in the control group. None of the patients were taking opioid analgesics. The medications used by patients in this age group were more likely to have anticholinergic properties than those used by older patients. [7]

In older adults, long-term use of anticholinergic drugs has been linked to cognitive impairment. A study in patients aged 65 years and older found that the risk for cognitive impairment was increased by 50% in those who had taken three or more mild anticholinergic drugs for more than 90 days and by 100% in those taking one or more strong anticholinergics for more than 60 days. [8, 9] The Drug Burden Index (DBI), a non-invasive method to quantify patients’ anticholinergic and sedative drug burden from their prescriptions, can be useful in older patients with polypharmacy. [10, 11]

Anticholinesterase inhibitors (eg, donepezil) are used in treatment of Parkinson disease dementia. Mantri et al reported that concurrent use of anticholinergic medications is a common prescribing error in these patients. [12]


Physical Examination

Anticholinergic syndrome results from the inhibition of muscarinic cholinergic neurotransmission. Clinical manifestations are caused by CNS effects, peripheral nervous system effects, or both.

Remember common signs and symptoms with the mnemonic, "red as a beet, dry as a bone, blind as a bat, mad as a hatter, hot as a hare, and full as a flask." The mnemonic refers to the symptoms of flushing, dry skin and mucous membranes, mydriasis with loss of accommodation, altered mental status (AMS), fever, and urinary retention, respectively.

Additional manifestations include the following:

  • Sinus tachycardia
  • Decreased bowel sounds
  • Functional ileus
  • Hypertension
  • Tremulousness
  • Myoclonic jerking

Patients with central anticholinergic syndrome may present with the following:

  • Ataxia
  • Disorientation
  • Short-term memory loss
  • Confusion
  • Hallucinations (visual, auditory)
  • Psychosis
  • Agitated delirium
  • Seizures (rare)
  • Coma
  • Respiratory failure
  • Cardiovascular collapse