Cholinergic Toxicity
Cholinergic toxicity results from excessive acetylcholine activity at muscarinic, nicotinic, and CNS receptors, most commonly caused by acetylcholinesterase inhibition from organophosphates, carbam…
Dr. Lucas Mastropaolo
Cholinergic toxicity results from excessive acetylcholine activity at muscarinic, nicotinic, and CNS receptors, most commonly caused by acetylcholinesterase inhibition from organophosphates, carbamates, nerve agents, or cholinesterase-inhibiting medications. [1-2] The classic presentation is remembered by the mnemonics SLUDGE (Salivation, Lacrimation, Urination, Defecation, GI cramping, Emesis) and DUMBBBELS (Diarrhea, Urination, Miosis, Bronchospasm/Bronchorrhea, Bradycardia, Emesis, Lacrimation, Salivation). Lethality is primarily driven by respiratory failure from bronchorrhea, bronchospasm, respiratory muscle paralysis, and central apnea. [2]
1. History
- Exposure source: Pesticide contact (occupational, agricultural, intentional ingestion), nerve agent exposure, medication overdose (pyridostigmine, neostigmine, donepezil, rivastigmine, distigmine) [2-4]
- Route: Ingestion, inhalation, dermal absorption — onset varies accordingly. Inhalation: seconds to minutes. Ingestion: 30–90 minutes. Dermal: up to 48 hours [2]
- Timing: When did symptoms begin? Rapid onset suggests inhalation or large ingestion; delayed onset suggests dermal exposure or fat-soluble agents [2]
- Quantity: Amount ingested, duration of exposure, concentration of product
- Symptom characterization: Excessive secretions (drooling, tearing, sweating), blurred vision, abdominal cramping, diarrhea, urinary incontinence, muscle twitching, weakness, difficulty breathing, confusion [5-6]
- Important negatives: Absence of dry mucous membranes, mydriasis, or urinary retention (which would suggest anticholinergic toxidrome instead)
- Intent: Accidental vs. intentional (suicidal ingestion is common in developing countries) [2][7]
2. Alarm Features
- Respiratory distress: Bronchorrhea, bronchospasm, apnea, or respiratory muscle paralysis — the primary cause of death [2]
- Seizures or status epilepticus [1][8]
- Cardiac arrest, bradycardia, or hypotension [1][8]
- Altered mental status or coma [5]
- Muscle fasciculations progressing to flaccid paralysis (nicotinic excess) [1]
- Intermediate syndrome: Severe proximal muscle weakness and respiratory failure occurring 1–4 days after initial recovery from cholinergic crisis — an important cause of delayed death [2][6]
- Copious secretions requiring aggressive suctioning
3. Medications
Causative agents
- Organophosphate pesticides (chlorpyrifos, diazinon, malathion) [2]
- Carbamate pesticides (carbaryl, aldicarb) [1]
- Nerve agents (sarin, soman, tabun, VX, Novichok) [2]
- Cholinesterase-inhibiting medications: pyridostigmine, neostigmine, physostigmine, donepezil, rivastigmine, distigmine [3-4][9]
Antidotes
- Atropine — mainstay; blocks muscarinic effects (bronchorrhea, bradycardia, bronchospasm). Does NOT reverse nicotinic effects (paralysis) [1][8]
- Pralidoxime (2-PAM) — reactivates acetylcholinesterase; addresses nicotinic effects. Must be given early before "aging" occurs [8][10]
- Benzodiazepines (diazepam first-line, midazolam) — for seizure control [1][8]
Contraindicated/Caution
- Succinylcholine — prolonged paralysis due to inhibited pseudocholinesterase; use rocuronium instead if paralysis needed [8]
- Morphine, theophylline, aminophylline, phenothiazines — avoid in organophosphate poisoning [10]
4. Diet
- NPO in acute setting due to risk of vomiting and aspiration
- Aggressive IV fluid resuscitation for volume losses from diarrhea, vomiting, and diaphoresis
- No specific long-term dietary considerations; chronic low-level occupational exposure warrants avoidance of contaminated food/water sources
5. Review of Systems
- Eyes: Miosis, blurred vision, eye pain, lacrimation [5]
- Respiratory: Dyspnea, wheezing, cough, copious secretions, chest tightness [2]
- GI: Nausea, vomiting, abdominal cramping, diarrhea, fecal incontinence [5]
- GU: Urinary incontinence [6]
- Neuro: Headache, confusion, agitation, seizures, weakness, fasciculations [2][5]
- Cardiovascular: Palpitations (tachycardia from nicotinic stimulation may predominate early), or bradycardia [5]
- Skin: Diaphoresis, localized fasciculations at dermal exposure site [2]
6. Collateral History and Family History
- Collateral: Witnesses to exposure, containers/bottles at scene, occupational setting, suicide note, co-exposed individuals
- Occupational history: Agricultural workers, pesticide applicators, chemical plant workers
- Social context: Access to pesticides, psychiatric history, prior suicide attempts
- Family history is generally not relevant unless considering pseudocholinesterase deficiency (butyrylcholinesterase deficiency), which can prolong effects of certain agents
7. Risk Factors
- Occupational exposure: Agricultural workers, pesticide handlers [2]
- Geographic: Higher incidence in South/Southeast Asia, China, Africa [7]
- Intentional self-harm: Leading cause of organophosphate poisoning globally [7]
- Medication-related: Patients on cholinesterase inhibitors (myasthenia gravis, Alzheimer's disease, neurogenic bladder) [3-4][9]
- Renal impairment and constipation: Risk factors for cholinergic crisis from distigmine [9]
- Lack of PPE in occupational settings
- Children: Increased susceptibility due to physiological and developmental factors [2]
8. Differential Diagnosis
- Carbamate poisoning — clinically indistinguishable from organophosphate poisoning; carbamates spontaneously dissociate (shorter duration) [1][6]
- Myasthenic crisis vs. cholinergic crisis — both present with muscle weakness; edrophonium (Tensilon) test and clinical judgment help differentiate [4][11]
- Nicotine poisoning — early cholinergic stimulation followed by ganglionic blockade [12]
- Mushroom poisoning (muscarinic mushrooms, e.g., Inocybe, Clitocybe) — SLUDGE symptoms without nicotinic features
- Serotonin syndrome — may share diaphoresis and altered mental status, but features clonus, hyperreflexia, and hyperthermia rather than miosis and secretions
- Opioid toxicity — shares miosis and respiratory depression but lacks secretions and fasciculations
- Acute gastroenteritis — may mimic GI symptoms but lacks the full toxidrome
9. Past Medical History
- Prior organophosphate or pesticide exposure
- Myasthenia gravis (on cholinesterase inhibitors)
- Alzheimer's disease (on donepezil, rivastigmine)
- Neurogenic bladder (on distigmine, bethanechol)
- Psychiatric history (depression, prior suicide attempts)
- Pseudocholinesterase deficiency
- Renal or hepatic impairment (affects drug metabolism)
10. Physical Exam
Vital signs
- Bradycardia (muscarinic) OR tachycardia (nicotinic — may predominate early) [5-6]
- Hypotension
- Tachypnea or apnea
- Hypothermia possible [9]
Focused exam
- Eyes: Miosis (pinpoint pupils) — hallmark finding [6]
- Oropharynx: Excessive salivation, drooling
- Lungs: Wheezing, rhonchi, copious secretions (bronchorrhea) — the most critical finding to monitor [1][8]
- Abdomen: Hyperactive bowel sounds, diffuse tenderness
- Skin: Profuse diaphoresis; localized fasciculations at dermal exposure site [2]
- Neuro: Fasciculations, muscle weakness, flaccid paralysis, altered mental status, seizures
- Neck flexor strength: Ask conscious patients to lift head off bed — weakness predicts impending respiratory failure (intermediate syndrome) [6]
- Odor: Garlic-like or petroleum/solvent smell may be present with pesticide ingestion
11. Lab Studies
- RBC (erythrocyte) cholinesterase — reflects true acetylcholinesterase inhibition; confirms severe intoxication [5-6]
- Serum (butyryl/pseudo) cholinesterase — more readily available but less specific; depressed in poisoning [5-6]
- ABG/VBG: Assess for hypoxemia, hypercarbia, metabolic acidosis
- BMP: Electrolyte abnormalities, renal function
- CBC: Leukocytosis; neutropenia in severe cases
- Lactate: Marker of tissue hypoperfusion
- Lipase/amylase: May be elevated [13]
- LFTs: Hepatic injury monitoring
- Serum glucose: Hypo- or hyperglycemia possible
- Toxicology screen: Rule out co-ingestants
- CPK: Rhabdomyolysis from fasciculations/seizures [13]
12. Imaging
- Chest X-ray: Assess for pulmonary edema, aspiration pneumonia, bronchorrhea-related opacities
- CT head: If altered mental status with unclear etiology or concern for co-ingestion
- Imaging is generally not diagnostic for cholinergic toxicity but helps identify complications
- No gold-standard imaging study exists for this condition
13. Special Tests
- Toxidrome recognition is the primary diagnostic tool — the combination of miosis + secretions + fasciculations + bradycardia is highly suggestive [2]
- Response to empirical atropine — improvement in secretions and bronchospasm supports the diagnosis [2]
- Edrophonium (Tensilon) test — used to differentiate cholinergic crisis from myasthenic crisis in patients on cholinesterase inhibitors [4][11]
- Point-of-care ultrasound: Assess cardiac function, volume status, lung B-lines
- Bedside spirometry/tidal volume monitoring: Tidal volume <5 mL/kg or vital capacity <15 mL/kg suggests need for intubation [6]
14. ECG
- Sinus bradycardia (muscarinic effect) — most classic finding
- Sinus tachycardia (nicotinic/sympathetic stimulation) — may predominate early [5]
- QTc prolongation — reported with organophosphate poisoning
- ST-segment changes — possible with myocardial ischemia from hypoxia
- Heart block — in severe cases
- Ventricular dysrhythmias — risk increased with hypoxia; atropine should not be given in the presence of significant hypoxemia due to risk of ventricular fibrillation [10]
- ECG should be obtained on all patients with suspected cholinergic toxicity and continuous cardiac monitoring maintained
15. Assessment
Severity stratification
- Mild: Miosis, lacrimation, salivation, diaphoresis, nausea — no respiratory compromise
- Moderate: Bronchospasm, vomiting, diarrhea, muscle fasciculations, mild weakness
- Severe: Respiratory failure, seizures, coma, cardiovascular collapse, paralysis [1-2]
Key clinical pearls
- The diagnosis is clinical — based on history, toxidrome recognition, and response to atropine [2]
- Nicotinic effects (tachycardia, mydriasis) may mask or confuse the classic muscarinic presentation early on [5]
- Delayed complications include the intermediate syndrome (1–4 days post-exposure) and organophosphate-induced delayed neuropathy (2–3 weeks) [2][6]
- Carbamate poisoning is generally shorter in duration due to spontaneous enzyme reactivation [1]
16. Treatment Plan
Initial stabilization (ABCs)
- Airway: Aggressive suctioning of secretions; early endotracheal intubation for respiratory failure — early intubation improves outcomes [1][8]
- Breathing: Supplemental O₂; mechanical ventilation as needed
- Circulation: IV access, fluid resuscitation, vasopressors if needed
Decontamination
- Don PPE before patient contact — healthcare workers can develop symptoms from secondary exposure [1][8]
- Remove all clothing; copious soap and water irrigation [1][8]
- Consider GI decontamination (activated charcoal) for recent ingestion if airway is protected [2]
Antidote therapy
Key treatment pearls
- Atropine: Much larger doses than typical ACLS dosing are required. Endpoint is drying of pulmonary secretions (clear chest on auscultation), NOT pupil size [1-2][8]
- Pralidoxime: High-dose regimens (2 g loading + 1 g/hr infusion) showed better survival than low-dose in RCTs. Oximes are NOT universally effective — limited by aging, agent-specific differences, and inability to cross the blood-brain barrier [8]
- Avoid succinylcholine if intubation is needed — use rocuronium or vecuronium instead [8]
- Maintain atropinization for at least 48 hours and until cholinesterase activity recovers [10]
- Monitor for recurring cholinergic crises from fat-soluble organophosphate redistribution for days to weeks [6]
17. Disposition
- ICU admission: All moderate-to-severe poisonings; any patient requiring atropine infusion, intubation, or with hemodynamic instability, seizures, or significant nicotinic symptoms [2][6]
- Observation (minimum 6–12 hours): Mild exposures with minimal symptoms; dermal exposures require extended observation (up to 48 hours) due to delayed absorption [2]
- Discharge criteria: Resolution of all cholinergic symptoms, stable vitals off atropine, adequate respiratory function, no evidence of intermediate syndrome
- Psychiatry consultation: Mandatory for all intentional ingestions before discharge
- Poison Control Center: Contact early (1-800-222-1222 in the US) [2]
- Toxicology consultation: For severe cases, unclear agent, or refractory symptoms
18. Follow Up / Return Precautions
- Intermediate syndrome monitoring: Patients should be warned about potential delayed respiratory failure 1–4 days after apparent recovery — return immediately for any new weakness, difficulty breathing, or neck weakness [2][6]
- Organophosphate-induced delayed neuropathy (OPIDN): Peripheral neuropathy may develop 2–3 weeks post-exposure; follow up for distal weakness or sensory changes [2]
- Follow-up timing: Outpatient follow-up within 1–2 days for mild cases; sooner if any recurrent symptoms
- Return precautions: Return for any recurrence of excessive secretions, difficulty breathing, muscle weakness, blurred vision, or confusion
- Occupational counseling: Ensure safe work practices, proper PPE use, and avoidance of re-exposure
- Mental health follow-up: Essential for intentional exposures
- Expected recovery: Carbamate poisoning typically resolves within 24–48 hours. Organophosphate poisoning may require days to weeks of ICU care depending on severity and specific agent [1-2]
References
1. 2023 American Heart Association Focused Update on the Management of Patients With Cardiac Arrest or Life-Threatening Toxicity Due to Poisoning: An Update to the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. — Lavonas EJ, Akpunonu PD, Arens AM, et al. Circulation. 2023.
2. Hazardous Chemical Emergencies and Poisonings. — Henretig FM, Kirk MA, McKay CA. The New England Journal of Medicine. 2019.
3. FDA Drug Label. — Updated date: 2025-12-23. Food and Drug Administration.
4. FDA Drug Label. — Updated date: 2020-12-31. Food and Drug Administration.
5. Acute Chemical Emergencies. — Kales SN, Christiani DC. The New England Journal of Medicine. 2004.
6. Management of Acute Organophosphorus Pesticide Poisoning. — Eddleston M, Buckley NA, Eyer P, Dawson AH. Lancet. 2008.
7. Management of Organophosphorus Poisoning: Standard Treatment and Beyond. — Aman S, Paul S, Chowdhury FR. Critical Care Clinics. 2021.
8. Part 10: Adult and Pediatric Special Circumstances of Resuscitation: 2025 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. — Cao D, Arens AM, Chow SL, et al. Circulation. 2025.
9. Unexpected Cholinergic Crisis Caused by Distigmine Bromide: A Case Report. — Sera T, Kusunoki S, Shime N. Medicine. 2022.
10. FDA Drug Label. — Updated date: 2026-04-01. Food and Drug Administration.
11. FDA Drug Label. — Updated date: 2024-10-15. Food and Drug Administration.
12. Chemical-Biological Terrorism and Its Impact on Children. — Chung S, Baum CR, Nyquist AC. Pediatrics. 2020.
13. Biochemical Responses as Early and Reliable Biomarkers of Organophosphate and Carbamate Pesticides Intoxication: A Systematic Literature Review. — Sepahi S, Gerayli S, Delirrad M, et al. Journal of Biochemical and Molecular Toxicology. 2023.