Muscarinic mushroom poisoning is an early-onset cholinergic toxidrome (typically within 15 minutes to 2 hours of ingestion) caused by muscarine found primarily in Inocybe spp. and Clitocybe spp. mushrooms. [1-3] It produces the classic SLUDGE/DUMBELS parasympathetic overstimulation syndrome. The specific antidote is atropine, and prognosis is excellent with supportive care — full recovery typically occurs within 6–24 hours. [1-2]
1. History
- What type of mushroom was consumed? Wild-foraged vs. store-bought? Any remaining specimens for mycologist identification?
- Timing of symptom onset relative to ingestion — muscarinic syndrome is characteristically early onset (15 min–2 hours), rarely up to 5 hours [1-2]
- Quantity consumed, preparation method (raw vs. cooked — cooking does not reliably destroy muscarine) [2]
- Symptom characterization: profuse sweating, salivation, tearing, diarrhea, abdominal cramping, blurred vision
- Who else ate the same mushrooms? (cluster exposures are common) [1-2]
- Intent: foraging, recreational, accidental (children), or intentional [4]
- Important negatives: absence of delayed symptoms (>6 hours) helps exclude amatoxin poisoning [5]
2. Alarm Features
- Severe bradycardia or hemodynamic instability — risk of circulatory collapse [3]
- Bronchospasm / bronchorrhea — airway compromise requiring intubation
- Syncope or altered mental status [1]
- Symptom onset >6 hours post-ingestion — raises concern for amatoxin (hepatotoxic) or orellanine (nephrotoxic) poisoning rather than pure muscarinic syndrome [5]
- Co-ingestion of multiple mushroom species (mixed toxidrome)
- Pediatric or elderly patients — higher risk of decompensation [6]
3. Medications
- Antidote: Atropine sulfate — FDA-approved for muscarinic mushroom poisoning [7]
- Adults: 1–6 mg IV/IM initially depending on severity; repeat every 3–5 minutes, doubling dose until response (drying of secretions, improved oxygenation). No maximum total dose [7]
- Pediatrics: 0.02–0.06 mg/kg IV/IM/IO; repeat every 5 minutes, doubling as needed [7]
- Maintenance: 10–20% of total loading dose per hour as continuous infusion [7]
- Supportive: IV fluids for dehydration, antiemetics (ondansetron)
- Contraindicated: Pralidoxime (2-PAM) is NOT indicated — there is no cholinesterase inhibition in muscarinic mushroom poisoning (unlike organophosphate poisoning) [8]
- Avoid anticholinergics with CNS effects (e.g., scopolamine) unless specifically indicated
4. Diet
- NPO initially if actively vomiting or hemodynamically unstable
- Aggressive oral and IV rehydration once tolerated — significant fluid losses from diarrhea, diaphoresis, salivation, and vomiting
- Advance diet as tolerated; bland diet during recovery
- Long-term: counsel against foraging wild mushrooms without expert mycologist identification
5. Review of Systems
- GI: Nausea, vomiting, diarrhea, abdominal cramping
- HEENT: Lacrimation, salivation, miosis, blurred vision [1]
- Respiratory: Wheezing, bronchorrhea, dyspnea
- Cardiovascular: Bradycardia (or paradoxical tachycardia), hypotension, syncope [1]
- Skin: Profuse diaphoresis, flushing
- GU: Urinary urgency/incontinence
- Neuro: Tremor, restlessness; altered mental status suggests co-ingestion of ibotenic acid/muscimol (Amanita muscaria) rather than pure muscarine [5-6]
6. Collateral History and Family History
- Critical: Identify all co-ingestors — cluster poisonings are the norm with foraged mushrooms [1-2]
- Obtain any remaining mushroom specimens or photographs for expert mycologist identification [1][9]
- Geographic location and season of foraging (Inocybe spp. are ubiquitous worldwide) [10]
- Family history is not directly relevant, though genetic polymorphisms may influence toxin metabolism [11]
- Social context: immigrant communities with foraging traditions may mistake local toxic species for edible species from their home country
7. Risk Factors
- Wild mushroom foraging — the primary risk factor; toxic Inocybe and Clitocybe species closely resemble edible mushrooms [12]
- Lack of expert mycological knowledge
- Seasonal exposure: late summer through fall [9]
- Geographic: temperate and tropical regions worldwide [10][13]
- Extremes of age (children with accidental ingestion; elderly with more severe presentations) [6]
- Recreational use of psychoactive mushrooms with misidentification
8. Differential Diagnosis
The key clinical distinction is early-onset (<6 hours) vs. delayed-onset (>6 hours) mushroom poisoning, as delayed onset suggests far more dangerous syndromes: [5]
- Organophosphate / carbamate poisoning — identical cholinergic toxidrome; distinguish by exposure history (pesticides, farming) and presence of nicotinic features (fasciculations, paralysis); pralidoxime is indicated here [8]
- Amatoxin poisoning (Amanita phalloides) — GI symptoms may overlap but onset is typically 6–24 hours; progresses to hepatorenal failure; this is the cannot-miss diagnosis [5]
- Cholinergic medication overdose — bethanechol, pilocarpine, donepezil
- Ibotenic acid/muscimol poisoning (Amanita muscaria) — predominantly CNS effects (agitation, sedation, hallucinations) rather than peripheral cholinergic signs; may have mixed features [4][6]
- GI-irritant mushroom poisoning — early-onset nausea/vomiting/diarrhea without cholinergic autonomic features [5]
- Gyromitrin poisoning (Gyromitra spp.) — GI symptoms with delayed hepatotoxicity and seizures [11]
- Infectious gastroenteritis — if mushroom ingestion history is not volunteered
9. Past Medical History
- Pre-existing cardiac disease — bradycardia and hypotension may be poorly tolerated; atropine dosing in coronary artery disease should be limited to 0.03–0.04 mg/kg total [14]
- Asthma/COPD — bronchospasm from muscarinic stimulation may be more severe
- Prior mushroom poisoning episodes
- Medications with cholinergic or anticholinergic properties (may mask or exacerbate symptoms)
- Hepatic or renal disease — relevant if co-ingestion of hepatotoxic/nephrotoxic species is suspected
10. Physical Exam
- Vitals: Bradycardia (classic), hypotension; tachycardia may occur paradoxically [1]
- Eyes: Miosis, lacrimation [1]
- Oropharynx: Profuse salivation (sialorrhea)
- Lungs: Wheezing, rhonchi, bronchorrhea — auscultate carefully for signs of pulmonary edema
- Abdomen: Hyperactive bowel sounds, diffuse cramping
- Skin: Diaphoresis, flushing, warm and wet (contrast with anticholinergic toxidrome: "dry as a bone")
- Neuro: Tremor, restlessness; if obtunded, consider mixed ingestion with ibotenic acid/muscimol [6]
- GU: Urinary incontinence
The mnemonic SLUDGE (Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis) or DUMBELS (Defecation, Urination, Miosis, Bronchospasm/Bronchorrhea, Emesis, Lacrimation, Salivation) captures the classic findings.
11. Lab Studies
- BMP: Electrolytes (hypokalemia from GI losses, dehydration), glucose, renal function
- LFTs: Baseline AST/ALT — critical to trend if any concern for co-ingestion of amatoxin-containing species; hepatotoxicity from pure muscarine is not expected acutely [5]
- CBC: Baseline
- Lipase: If significant abdominal pain
- Lactate: If hemodynamically unstable
- Coagulation studies (PT/INR): If hepatotoxicity is a concern
- Urinalysis
- No specific serum muscarine assay is routinely available clinically; UPLC-MS/MS can detect muscarine in research settings [2]
12. Imaging
- Chest X-ray: If bronchospasm, bronchorrhea, or respiratory distress — evaluate for pulmonary edema
- Abdominal imaging: Generally unnecessary unless concern for surgical abdomen or alternative diagnosis
- CT head: Only if altered mental status is disproportionate to expected toxidrome
Imaging is typically not required for straightforward muscarinic mushroom poisoning.
13. Special Tests
- Poison Control Center consultation — recommended for all mushroom poisoning cases
- Expert mycologist identification of remaining mushroom specimens — the single most important diagnostic step [1-2][9]
- Acetylcholinesterase levels (RBC and plasma): Normal in muscarinic mushroom poisoning; depressed in organophosphate/carbamate poisoning — useful to distinguish these entities [8]
- Urine amatoxin assay: If any concern for co-ingestion or delayed-onset symptoms
14. ECG
- Sinus bradycardia — most common finding
- Prolonged PR interval possible
- Monitor for high-degree AV block — atropine may be ineffective in type II second-degree or third-degree AV block with wide QRS [7]
- ST/T-wave changes may occur secondary to hypotension or in patients with underlying coronary disease
- ECG is indicated in all symptomatic patients to guide atropine therapy
15. Assessment
Muscarinic mushroom poisoning is classified as Group 2B (autonomic-toxicity) in the proposed clinical classification of mushroom poisoning syndromes. [5] Key clinical features:
- Rapid onset (15 min–2 hours, rarely up to 5 hours) distinguishes it from the more dangerous delayed-onset syndromes [1]
- Predominantly peripheral cholinergic toxidrome without nicotinic features
- Severity ranges from mild GI symptoms to life-threatening bronchospasm and cardiovascular collapse [3]
- Prognosis is excellent — full recovery within 6–24 hours with supportive care and atropine [1-2]
- Deaths are rare but can occur from severe bronchospasm or circulatory collapse, particularly in elderly patients or those with delayed treatment [3]
- The primary danger lies in misidentification — failing to recognize co-ingestion of amatoxin-containing species that may present with overlapping early GI symptoms
16. Treatment Plan
Initial stabilization
- ABCs — suction airway secretions; intubate if severe bronchorrhea/bronchospasm
- Continuous cardiac monitoring, pulse oximetry
- IV access, aggressive fluid resuscitation
Antidote — Atropine: [7]
- Adults: 1–6 mg IV initially; repeat every 3–5 minutes, doubling dose until secretions dry and oxygenation improves
- Pediatrics: 0.02–0.06 mg/kg IV; repeat every 5 minutes
- Maintenance infusion: 10–20% of loading dose per hour
- Titrate to secretion control, not heart rate
- No maximum total dose
Decontamination
- Activated charcoal (1 g/kg, max 50 g) if within 1–2 hours of ingestion and airway is protected
- Gastric lavage rarely indicated
Supportive care
- IV fluids for volume depletion
- Antiemetics (ondansetron 4 mg IV)
- Electrolyte repletion as needed
- Benzodiazepines for agitation/tremor
17. Disposition
- Admit / observe if:
- Hemodynamic instability or significant bradycardia requiring atropine
- Respiratory compromise (bronchospasm, bronchorrhea)
- Uncertain mushroom identification — must observe for delayed hepatotoxicity (serial LFTs at 12–24 hours)
- Pediatric or elderly patients
- Atropine infusion required
- Discharge may be considered if:
- Mild symptoms that resolve completely with observation (typically 6–12 hours)
- Mushroom species confidently identified as muscarine-containing only (no amatoxin risk)
- Tolerating oral fluids, stable vitals
- Consult: Poison Control Center, toxicology, mycologist [1][9]
18. Follow Up / Return Precautions
- Follow-up: Primary care within 2–3 days if discharged
- Return immediately for: recurrence of profuse sweating/salivation, difficulty breathing, abdominal pain, jaundice (suggests hepatotoxicity from co-ingested species), dark urine, or decreased urine output
- Expected recovery: Full resolution within 6–24 hours for pure muscarinic poisoning [1-2]
- Counseling: Strongly advise against foraging wild mushrooms without expert identification; toxic Inocybe and Clitocybe species closely resemble edible mushrooms [12]
- Report to local poison control center for epidemiologic tracking
References
1. Mushroom Poisoning From Species of Genus Inocybe (Fiber Head Mushroom): A Case Series With Exact Species Identification. — Lurie Y, Wasser SP, Taha M, et al. Clinical Toxicology. 2009.
2. Mushroom Poisoning From Inocybe Serotina: A Case Report From Ningxia, Northwest China With Exact Species Identification and Muscarine Detection. — Xu F, Zhang YZ, Zhang YH, et al. Toxicon : Official Journal of the International Society on Toxinology. 2020.
3. The Fatal Mushroom Neurotoxin Muscarine Is Released From a Harmless Phosphorylated Precursor Upon Cellular Injury. — Dörner S, Trottmann F, Jordan PM, et al. Angewandte Chemie. 2024.
4. Toxicity of Muscimol and Ibotenic Acid Containing Mushrooms Reported to a Regional Poison Control Center From 2002-2016. — Moss MJ, Hendrickson RG. Clinical Toxicology. 2019.
5. Mushroom Poisoning: A Proposed New Clinical Classification. — White J, Weinstein SA, De Haro L, et al. Toxicon : Official Journal of the International Society on Toxinology. 2019.
6. Acute Amanita Muscaria Toxicity: A Literature Review and Two Case Reports in Elderly Spouses Following Home Preparation. — Stoeva-Grigorova S, Yarabanova I, Radeva-Ilieva M, et al. Toxins. 2025.
7. FDA Drug Label. — Updated date: 2024-10-11. Food and Drug Administration.
8. Hazardous Chemical Emergencies and Poisonings. — Henretig FM, Kirk MA, McKay CA. The New England Journal of Medicine. 2019.
9. A 25-Year Analysis of Armillaria (Honey Mushroom) Poisoning in Wisconsin. — Feldman R, Audette M, Leacock PR, Theobald J. The American Journal of Emergency Medicine. 2026.
10. Evolution of the Toxins Muscarine and Psilocybin in a Family of Mushroom-Forming Fungi. — Kosentka P, Sprague SL, Ryberg M, et al. PloS One. 2013.
11. A 19-Year Longitudinal Assessment of Gyromitrin-Containing (Gyromitra Spp.) Mushroom Poisonings in Michigan. — Vohra V, Dirks A, Bonito G, James T, Carroll DK. Toxicon : Official Journal of the International Society on Toxinology. 2024.
12. Toxic Metabolite Profiling of Inocybe Virosa. — Sai Latha S, Shivanna N, Naika M, et al. Scientific Reports. 2020.
13. A New Muscarine-Containing (Inocybaceae, Agaricales) Species Discovered From One Poisoning Incident Occurring in Tropical China. — Deng LS, Yu WJ, Zeng NK, et al. Frontiers in Microbiology. 2022.
14. FDA Drug Label. — Updated date: 2025-10-08. Food and Drug Administration.