Canis ISSN: 2398-2942

Metaldehyde poisoning

Synonym(s): Slug pellets, molluscicide

Contributor(s): Larry Thompson


  • Molluscicide, rat poison.
  • Signs: similar to organophosphate or carbamate poisoning.
  • Diagnosis: history, clinical signs.
  • Treatment: symptomatic - no specific antidote.
  • Prognosis: guarded - fatal outcomes are more common with this agent than any other.



  • Accidental ingestion of granules containing 5-10% metaldehyde.
  • Some major brands and certain formulations contain a cat and dog repellent.
  • Cases often seen after a wet weekend when snails/slugs emerge and gardeners apply carbamate-based snail/slug baits.
  • There is an increasing number of cases of metaldehyde poisoning attributed to its malicious use in baits, particularly meat-based baits.


  • Lowest reported toxic consumption is 60 mg/kg.
  • Mechanism of action is not fully understood.
  • Hydrolysed in stomach to acetaldehyde - LD50 500 mg/kg.
  • Acetaldehyde and metaldehyde can cross blood-brain barrier and can affect neurotransmission in brain.
  • Other factors may contribute to mortality:
    • Hyperthermia from the increased muscular activity can lead to severe body temperature rises (above 107°F (41.7°C)) and result in cellular necrosis within minutes.
    • Severe metabolic acidosis Acid base imbalance may be the underlying cause of the hyperpnea and CNS depression seen in severe poisonings. The acidosis may result from the acidic nature of the toxicant itself.
  • Death usually results from respiratory failure.


  • Signs usually develop 1-3 h after ingestion.
  • Can have delayed renal or hepatic damage (5-14 days later).
  • In severe cases death may occur in hours.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Campbell A (2008) Metaldehyde poisoning of dogs. Vet Rec 163 (11), 343 PubMed.
  • Mills N J (2008) Metaldehyde poisoning of dogs. Vet Rec 163 (10), 310 PubMed.
  • Yas-Natan E, Segev G, Aroch I (2007) Clinical, neurological and clinicopathological signs, treatment and outcome of metaldehyde intoxication in 180 dogs. JSAP 48 (8), 438-443 PubMed.
  • Cope R B, White K S, More E, Holmes K, Nair A, Chauvin P, Oncken A (2006) Exposure-to-treatment interval and clinical severity in canine poisoning: a retrospective analysis at a Portland veterinary emergency center. J Vet Pharmacol Ther 29 (3), 233-236 PubMed.
  • Steenbergen V M (2004) Taking the bait: metaldehyde toxicosis. Vet Tech 25 (4), 259-261 ResearchGate.
  • Dolder L K (2003) Metaldehyde toxicosis. Vet Med 98 (3), 213-215 VetMedResource.
  • Shintani S, Goto K, Endo Y, Iwamoto C, Ohata K (1999) Adsorption effects of activated charcoal on metaldehyde toxicity in rats. Vet Hum Toxicol 41 (1), 15-18 PubMed.
  • Tardieu D, Thouvenot N, Fargier C, de Saqui-Sannes P, Petit C (1996) Phenobarbital-type P450 inducers protect rats against metaldehyde toxicity. Vet Hum Toxicol 38 (6), 454-456 PubMed.
  • Mayer S (1991) Poison Metaldehyde [a molluscicide]. In Practice 13 (2), 57 VetMedResource.
  • Von Burg R, Stout T (1991) Metaldehyde. J Appl Toxicol 11 (5), 377-378 PubMed.
  • Davies S M A, Lawrence K E (1989) Metaldehyde poisoning. Vet Rec 124 (24), 643 PubMed.
  • Booze T F, Oehme F W (1986) An investigation of metaldehyde and acetaldehyde toxicities in dogs. Fundam Appl Toxicol 6 (3), 440-446 PubMed.
  • Rose I R B (1986) Anaesthetic control for metaldehyde poisoning. Vet Rec 119 (15), 388 PubMed.
  • Webster C J, Webster J M (1986) Anaesthetic control for metaldehyde poisoning. Vet Rec 119 (20), 511-512 PubMed.
  • Booze T F, Oehme F W (1985) Metaldehyde toxicity: a review. Vet Hum Toxicol 27 (1), 11-19 PubMed.
  • Cruikshank A K (1982) Metaldehyde and paraquat poisoning. Vet Rec 111 (7), 149-150 PubMed.
  • Homeida A M, Cooke R G (1982) Anti-convulsant activity of diazepam and clonidine on metaldehyde-induced seizures in mice: effects on brain gamma-amino butyric acid concentrations and monoamine oxidase activity. J Vet Pharmacol Therap 5 (3), 187-190 PubMed.
  • Foley A J (1981) Metaldehyde pet poisonings. NZ Vet J 29 (10), 185 PubMed.
  • Homeida A M, Cooke R G (1981) Pharmacological aspects of metaldehyde poisoning in mice. J Vet Pharmacol Therap 5 (1), 77-81 PubMed.
  • Blaine D R (1977) Treatment of metaldehyde poisoning in dogs with megadoses of acepromazine maleateVet Med Sm Anim Clin 72 (6), 1009-1011 PubMed.
  • Bishop C H G (1975) Letter: Blindness associated with metaldehyde poisoning. Vet Rec 96 (19), 438 PubMed.
  • Turner T (1973) Letter: Toxicity of metaldehyde to dogs. Vet Rec 93 (19), 524 PubMed.
  • Udall N D (1973) The toxicity of the molluscicides metaldehyde and methiocarb to dogs. Vet Rec 93 (15), 420-422 PubMed.
  • Turner T (1967) Metaldehyde poisoning in the dog. Vet Rec 80 (4), 184 PubMed.
  • Darbishire H B (1966) Danger to dogs of metaldehyde pellets. Vet Rec 79 (26), 860 PubMed.

Other sources of information

  • Campbell A and Chapman M (2000) Handbook of poisoning in dogs and cats. Blackwell Science. 181-185.
  • Poppenga R (1999)T oxicological Emergencies. In: Manual of Canine and Feline Emergency and Critical Care. Eds L King and Hammond. BSAVA publication. pp 219-232.
  • Oehme F W (1987) Clinical Toxicology in small animals. In:Veterinary Clinical Toxicology, Proceedings No 103, University of Sydney, Australia. pp 443-47.
  • Lorgue G, Lechenet J & Reviere, A (1966) Clinical Veterinary Toxicology.Oxford: Blackwell Scientific Publications. pp 132-133.