Page 1134 - Cote clinical veterinary advisor dogs and cats 4th

566 Ivermectin Toxicosis

Client Education SUGGESTED READING AUTHOR: Valentina Merola, DVM, MS, DABVT, DABT
Vitamins may be palatable and need to be kept Hall JO: Iron. In Peterson ME, et al, editors: Small EDITOR: Tina Wismer, DVM, MS, DABVT, DABT
VetBooks.ir pp 595-600.
away from dogs.
animal toxicology, ed 3, St. Louis, 2013, Saunders,

Ivermectin Toxicosis Client Education
Sheet

BASIC INFORMATION GEOGRAPHY AND SEASONALITY Differential Diagnosis
Animals in rural areas or living on or near Toxic differentials:
Definition farms may have increased access to large-animal • Alcohol
An acute or subacute intoxication resulting formulations of ivermectin. • 5-Hydroxytryptophan
from accidental overdose, inappropriate owner Clinical Presentation • Amitraz
administration, or ingestion of a common veteri- • Marijuana
nary anthelmintic; characterized by neurologic HISTORY, CHIEF COMPLAINT • Smooth muscle relaxants
signs • History of intentional administration or • Barbiturates
accidental ingestion • Organophosphates or carbamate insecticides
Synonyms • Sudden onset of ataxia, visual difficulties, Nontoxic differentials:
Agri-Mectin, Bimectin, DuraMectin, Eqvalan, depression • Meningitis
EquiMax, Equimectrin, Heartgard, Iverhart, • Intracranial neoplasia
Ivomec, Tri-Heart, Vethical, Vetrimec, Zimectrin PHYSICAL EXAM FINDINGS • Portosystemic shunt
• CNS
Epidemiology ○ Depression Initial Database
SPECIES, AGE, SEX ○ Coma • CBC, serum chemistry profile, urinalysis:
• Although any animal is susceptible, toxic- ○ Ataxia typically unremarkable
ity occurs far more often in dogs than ○ Tremors ○ Monitor for hypernatremia with repeated
cats. ○ Seizures doses of activated charcoal.
• Young animals may be more suscep- ○ Disorientation • Pulse oximetry and/or arterial blood gas if
tible due to a more penetrable blood-brain • Visual suspect hypoventilation
barrier. ○ Mydriasis • Thoracic radiographs if suspect aspiration
○ Blindness
GENETICS, BREED PREDISPOSITION • Cardiovascular Advanced or Confirmatory Testing
Breeds that have mutation in the MDR1/ ○ Bradycardia • Ivermectin can be detected in liver, adipose,
ABCB1-Δ gene (p. 638) that encodes for trans- • Gastrointestinal tissue, or serum
membrane pump P-glycoprotein responsible for ○ Vomiting • ABCB1 gene testing for suspected breed
keeping drugs out of the central nervous system ○ Hypersalivation sensitivity at Washington State University
(CNS) are more susceptible to intoxication: • Respiratory Veterinary Clinical Pharmacology Lab (vcpl.
• Collies ○ Hypoventilation vetmed.wsu.edu)
• Long-haired whippet • Nonspecific
• Australian shepherd ○ Dehydration TREATMENT
• Miniature Australian shepherd ○ Hypothermia (with recumbency)
• McNab shepherd ○ Hyperthermia (with tremors/seizures) Treatment Overview
• Silken windhound Decontamination and monitoring is key for
• English shepherd Etiology and Pathophysiology animals presented with no clinical signs but
• Shetland sheepdog • Ivermectin binds to glutamate-gated chloride known recent exposure. For patients already
• German shepherd ion channels in nerve and muscle cells, demonstrating signs of intoxication, care is
• Old English sheepdog leading to hyperpolarization and ultimately largely symptomatic and supportive. Lipid
• Border collie paralysis and death of invertebrates. emulsion therapy may be tried for more severely
• Mixes of these breeds • In mammals, gamma-aminobutyric acid affected patients.
(GABA)–mediated chloride channels that
RISK FACTORS are sensitive to ivermectin are found in Acute General Treatment
• Genetic susceptibility (i.e., ABCB1 gene the CNS, which is normally protected by • Decontamination in asymptomatic patient
mutation) the blood-brain barrier and appropriately (p. 1087)
• Pet owners’ use of large-animal ivermectin functioning P-glycoprotein. When normal ○ Induce emesis (p. 1188): apomorphine
products for pet animals or access of dogs protective mechanisms are overwhelmed 0.03 mg/kg IV or 0.04 mg/kg IM (canine)
to large-animal products (e.g., dog licking or protective mechanisms do not function ○ Gastric lavage in large exposures (p. 1117)
up flavored horse-product dropped on the correctly, toxicosis occurs. ○ Activated charcoal 1-2 g/kg q 8h PO for
ground) 1-2 days
• Dogs put on increasing doses of ivermectin DIAGNOSIS • Excision may be attempted for recent
for demodectic mange can develop clinical subcutaneous injections
signs due to the long half-life of ivermectin Diagnostic Overview • Control tremors/seizures
in the dog. Diagnosis is typically based on presenting ○ Methocarbamol 22-55 mg/kg IV, may
• Veterinary miscalculation when giving an clinical signs and known exposure or potential need to go up to 150 mg/kg IV if signs
injection (decimal point error) access to ivermectin. are severe

www.ExpertConsult.com