Canis ISSN: 2398-2942

Ivermectin toxicity

Contributor(s): Alexander Campbell, Lisa Moore

Introduction

  • GABA (gamma aminobutyric acid) agonist.
  • Collie, Shepherd dog and Sheltie breeds and related cross breeds are unusually sensitive to toxic effects. This sensitivity is conferred by a genetic deletion Multi-drug resistance gene (MDR1): overview.
  • Signs: nervous signs, muscle tremors, ataxia, stupor, coma and death.
  • Diagnosis: history, clinical signs.
  • Treatment: no antidote - treatment is symptomatic, though lipid rescue techniques have been deployed successfully.
  • Prognosis: death comparatively rare with supportive treatment.

Pathogenesis

Etiology

  • Poisoning usually the result of iatrogenic overdose.
  • Occasionally due to ingestion of horse anthelmintic.

Pathophysiology

  • Ingestion of a toxic dose has a direct effect on the brain.
  • Most clinical signs of overdosage can be attributed to the increased effects of GABA.

Timecourse

  • Signs appear 2-24 hours after ingestion.
  • Persist for 3 days to more than a week.
  • Following oral exposures peak plasma concentrations occur 3-5 hours post-ingestion and elimination half-life is between 76-80 hours.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • González Canga A, Sahagún Prieto A M, José Diez Liébana M, Martínez N F, Vega M S, Vieitez J J (2009) The pharmacokinetics and metabolism of ivermectin in domestic animal species. Vet J 179 (1), 25-37 PubMed.
  • Kenny P J, Vernau K M, Puschner B, Maggs D J (2008) Retinopathy associated with ivermectin toxicosis in two dogs. J Am Vet Med Assoc 233 (2), 279-284 PubMed.
  • Gokbulut C, Karademir U, Boyacioglu M, McKellar Q A (2006) Comparative plasma dispositions of ivermectin and doramectin following subcutaneous and oral administration in dogs. Vet Parasitol 135 (3-4), 347-54 PubMed.
  • Hopper K, Aldrich J & Haskins S C (2002) Ivermectin toxicity in 17 collies. JVIM 16 (1), 89-94 PubMed.
  • Mealey K L, Bentjen S A, Gay J M, Cantor G H (2001) Ivermectin sensitivity in collies is associated with a deletion mutation of the mdr1 gene. Pharmacogenetics 11 (8), 727-733 PubMed.
  • Hopkins K D, Marcella K L & Strecker A E (1990) Ivermectin toxicosis in a dog. JAVMA 197 (1), 93-94 PubMed.
  • Lovell R A (1990) Ivermectin and Piperazine toxicoses in dogs and cats. Vet Clin North Am Sm Anim Prac 20 (2), 453-468 PubMed.

Other sources of information

  • Baker L (2008) Lipid emulsion treatment of ivermectin in a dog. www.lipidrescue.squarespace.com/post-your-cases/post/510768Accessed 26/12/2008.
  • Mealey K L (2008) Ivermectin: macrolide antiparasitic agents.In:Small Animal Toxicology, 2nd edition. M E Peterson, P A Talcott (eds). St Louis: Elsevier Saunders.
  • Lorenz M & Cornelius L M Small Animal Medical Diagnosis. Lippincott. ISBN-0-397-50555-8.

Organisation(s)


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