Toxin

Metaldehyde Poisoning

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Metaldehyde Poisoning, Metaldehyde Toxicity, Metaldehyde Ingestion, Metaldehyde

  • Background
  1. Acetaldehyde polymer used as a molluscicide, targeting small slugs and snails
  2. Highly toxic to small animals
  3. May cause serious toxicity in humans with large exposures
  • Mechanism
  • Toxicity
  1. Metaldehyde (and metabolites) decrease CNS GABA synthesis
  2. Metaldehyde metabolites increase MAO activity and increased oxygen free radicals
  • Pharmacokinetics
  1. Routes of toxicity
    1. Ingestion and gastrointestinal absorption (within 1-4 hours)
    2. Transdermal
    3. Inhalational
    4. Enterohepatic recirculation increases Elimination Half-Life (up to 27 hours)
  2. Metaldehyde and its metabolites concentrate in the liver and CNS
  3. Metabolites
    1. Metaldehyde is hydrolyzed to acetaldehyde by hepatic CYP enzymes
  • Adverse Effects
  • General
  1. Nausea
  2. Vomiting
  3. Diarrhea
  • Adverse Effects
  • Neurotoxicity
  1. Generalized Tonic Clonic Seizures
    1. Occurs with ingestions >100 mg/kg
    2. Intentional ingestions are associated with a higher risk of Seizures (RR 3)
  2. Coma with increased mortality
    1. Occurs with ingestions >400 mg/kg
  3. Other neurologic adverse effects
    1. Facial Dystonia
    2. Altered Level of Consciousness
    3. Hyperreflexia
  • Labs
  1. See Unknown Ingestion for toxicology labs (e.g. EKG, chemistry, bedside Glucose, acetaminphen level)
  2. Serum Metaldehyde levels are NOT typically available
  • Management
  1. Multidose Activated Charcoal for ingestions (due to enterohepatic circulation)
    1. Activated Charcoal 1 g/kg then 0.5 g/kg every 6 hours for 48 hours
    2. Requires alert, cooperative patient or secured airway (e.g. Endotracheal Intubation)
  2. Seizures (GABA Agonists)
    1. See Status Epilepticus
    2. Benzodiazepines
    3. Barbiturates
    4. Propofol
  3. Disposition
    1. Observe patients for at least 6 hours
    2. Asymptomatic patients may be discharged after 6 hour observation
    3. Admit all symptomatic patients or intentional Overdose
  • References
  1. Carroll and Yakey (2025) Crit Dec Emerg Med 39(7): 34
  2. Tan (2022) Acute Med Surg 9(1):e766 +PMID: 35769386 [PubMed]
  3. Bleakley (2008) Emerg Med J 25(6):381-2 +PMID: 18499834 [PubMed]