Anticholinergic toxicity

(Redirected from Anticholinergics)


Datura stramonium aka Jimson Weed
Amanita phalloides aka "death cap"

Anticholinergic toxicity Causes

Clinical Features

  • Red as a beet: cutaneous vasodilation
  • Blind as a bat: nonreactive mydriasis (often delayed 12-24hr)
  • Mad as a hatter: delirium; attention deficit; hallucinations; dysarthria; lethargy
  • Full as a flask: urinary retention
  • Hot as a hare: anhydrotic hyperthermia (may become severe w/ agitation)
  • Dry as a bone: anhidrosis (esp axillae, mouth)
  • And the heart runs alone: Tachycardia (HR 120-160) and decreased/absent bowel sounds
  • ECG
    • Sinus tachycardia
    • QRS widening in some cases

Differential Diagnosis

Toxidrome Chart

Finding Cholinergic Anticholinergic Sympathomimetic Sympatholytic^ Sedative/Hypnotic
Example Organophosphates TCAs Cocaine Clonidine ETOH
Temp Nl Nl / ↑ Nl / ↑ Nl / ↓ Nl / ↓
RR Variable Nl / ↓ Variable Nl / ↓ Nl / ↓
HR Variable ↑ (sig) Nl / ↓ Nl / ↓
BP Nl / ↓ Nl / ↓
LOC Nl / Lethargic Nl, agitated, psychotic, comatose Nl, agitated, psychotic Nl, Lethargic, or Comatose Nl, Lethargic, or Comatose
Pupils Variable Mydriatic Mydriatic Nl / Miotic
Motor Fasciculations, Flacid Paralysis  Nl Nl / Agitated Nl
Skin Sweating (sig) Hot, dry Sweating Dry
Lungs Bronchospasm / rhinorrhea Nl Nl Nl
Bowel Sounds Hyperactive (SLUDGE) ↓ / Absent Nl / ↓ Nl / ↓
^Consider Sympatholytic when looking at Sedative OD or someone who doesn't respond to Narcan
Withdrawal from substances have the opposite effect

Altered mental status and fever


  • Consider GI decon with Activated Charcoal if patient presents <2 hours after ingestion and remains cooperative


  • Decreases the risk of hyperthermia, rhabdo, traumatic injuries
  • Benzos are agents of choice especially increase seizure threshold[2]
    • Repeat boluses every 5-15 minutes as needed to halt seizures and provide adequate sedation
    • Goal: QRS duration < 110 msec

Cholinesterase inhibition

  • Indicated for severe agitation or delirium (esp if unresponsive to benzos)
  • Contraindicated in QRS>100 or Na blockade signs (R' in aVR) and in narrow angle glaucoma
  • Relatively contraindicated in asthma or ileus
  • Physostigmine - strongly consider poison control consult before giving
    • Crosses blood brain barrier, can be used to help make dx
    • Dosing: 0.5mg-1mg IV over 5min (repeat dosing up to 2mg in first hour)[3]
    • Onset of action: 5-10min
    • If partial response, repeat x3
    • If 3 or more administrations are needed over a 6-hour period, start IV infusion (bolus 1-2 mg followed by 1 mg/hour)
    • Stop infusion every 12 hours to determine resolution of the toxidrome
    • Side effects: bradycardia, dysrhythmias, cholinergic excess[4]
    • Always have atropine at the bedside for bradycardia or cholinergic excess</ref>[5]
    • Contraindicated in TCA toxicity (associated with cardiac arrest) and in the presence of bradycardia or AV block

Other therapies

  • Sodium bicarbonate for conduction abnormalities (QRS prolongation)
    • 2 mEq/kg bolus (typically 2-3 amps of bicarb)
    • Begin continuous NaCO3 infusion at 250mL/hr if bolus effective
    • Solution preparation = 1L D5W mixed with 3 ampules NaHCO3


  • Consider discharge for patients with mild symptoms after 6hr obs if their symptoms resolve
  • Long-acting agents, plant seeds and large ingestions should have extended observation up to 24-48 hours even if asymptomatic due to decreased gastrointestinal motility
  • Admit if physostigmine was given (half-life of physo is often shorter than the ingested drug)
  • Patients may be cleared if symptoms do not recur within 6 hours of the last antidote dose

See Also


  1. Dawson AH, Buckley NA. Pharmacological management of anticholinergic delirium – theory, evidence and practice. Br J Clin Pharmacol. 2015;81(3):516-24.
  2. Burns MJ, et al. A comparison of physostigmine and benzodiazepines for the treatment of anticholinergic poisoning. Ann Emerg Med. 2000:35(4):374-381.
  3. Rosenbaum C and Bird SB. Timing and frequency for physostigmine redosing for antimuscarininc toxicity. J Med Toxicol. 2010;6:386-92.
  4. Pentel P and Peterson CD. Aystole complicating physostigmine treatment of tricyclic antidepressant overdose. Ann Emerg Med. 1980 Nov;9(11):588-90.
  5. Nguyen TT, et al. Adverse events from physostigmine: an observational study. Am J Emerg Med. 2018;36:141-2.