Anticholinergic toxicity

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Anticholinergic toxicity

Clinical Features

  • Dry as a bone: anhidrosis (esp axillae, mouth)
  • Hot as a hare: anhydrotic hyperthermia (may become severe w/ agitation)
  • 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
  • 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 Varriable 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


  1. GI decon
  2. Sedation
    • Decreases the risk of hyperthermia, rhabdo, traumatic injuries
    • Benzos are agents of choice especially increase seizure threshold
  3. Conduction abnormalities (QRS prolongation)
    • Sodium bicarbonate
      • Should be given at 2 mEq/kg
      • Typically 2-3 amps of bicarb
      • Begin continuous NaCO3 infusions if bolus effective
      • Solution preparation = 1L D5W mixed with 3 ampules NaHCO3
      • Run NaHCO3 solutions at 250 mL/hr
  4. Cholinesterase inhibition
    • Indicated for severe agitation or delirium (esp if unresponsive to benzos)
    • Contraindicated in QRS>100 or Na blockade signs (R' in aVR)
    • Relative 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: 0.5-2mg IV over 5min
      • Onset of action: 15-20min
      • Side effects: bradycardia, dysrhythmias, cholinergic excess
      • Always have atropine at the bedside for bradycardia or cholinergic excess
      • Contraindicated in TCA toxicity, associated with cardiac arrest


  • Consider discharge for patients with mild symptoms after 6hr obs if their symptoms resolve
  • Admit if physostigmine was given (half-life of physo is often shorter than the ingested drug)

See Also



Ross Donaldson