In this VETgirl online veterinary continuing education blog, we review ivermectin toxicity in a cat. In this video, a 10-year-old, male neutered, Domestic Long Hair presented to the emergency services for ivermectin toxicity. The owner had given this cat an equine dewormer containing ivermectin 1.87% and praziquantel 14.03%. The equine dewormer syringe contained 120.1 mg ivermectin and 897.6 mg of praziquantel. The owner administered 1/4 teaspoon in cat food to share between all 5 cats; however, it was estimated that this particular cat ingested 40-50% of the food; this made potential ingestion (worst case scenario of the whole amount ingested) of approximately 3 mg/kg of ivermectin. Previously, the owner had dewormed her cats this way in the past without any complications. This was dosed earlier in the day, and the cat developed ataxia and an inappropriate mentation with several hours. The ASPCA Animal Poison Control Center was consulted for life-saving advice.
While the active ingredient, praziquantel, was not of concern, the ivermectin dose was consistent with the development of clinical signs of ivermectin toxicosis. While most cats handle high-dose ivermectin well, clinical signs can be seen in normal healthy cats above 2.5 mg/kg. Clinical signs of ataxia, mydriasis, and vomiting can be seen, while at higher doses > 5 mg/kg, tremors, blindness, seizures, respiratory failure, and coma can be seen.
On presentation, the cat was obtunded, recumbent, had intermittent muscle tremors, and lacked a menace bilaterally. A normal direct and consensual pupillary light response was present bilaterally. Upon IV catheter placement, the cat became agitated, so butorphanol (at 0.3 mg/kg IV) was administered.
As ivermectin is considered lipophilic, a trial of intravenous lipid emulsion (ILE) was administered to create a "lipid sink." A 20% ILE solution was dosed at 1.5 mL/kg over 3 minutes, then at 0.5mL/kg/hr ILE for 30 minutes. As there was no signs of clinical improvement, an additional dose of ILE was repeated several hours later. While ILE isn’t meant to be the end-all, be-all antidote for fat-soluble toxins, it can often be effective in treating patients with ivermectin toxicosis. Unfortunately, no dramatic improvement in clinical signs was seen with the ILE; however, with supportive care, the cat was discharged 72 hours-post ingestion with mild persistent ataxia.
When in doubt, call the ASPCA Animal Poison Control Center for life-saving advice 24/7 with any poisoning situation. For more life-saving advice, check out VETgirl's other videos.