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.