Anticholinergic toxicity

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Anticholinergic toxicity Causes

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 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
  • Sedation
    • Decreases the risk of hyperthermia, rhabdo, traumatic injuries
    • Benzos are agents of choice especially increase seizure threshold
  • 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
  • Cholinesterase inhibition
    • Indicated for severe agitation or delirium (esp if unresponsive to benzos)
    • Contraindicated in QRS>100 or Na blockade signs (R' in aVR)
    • 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: 0.5-2mg 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