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Treating permethrin toxicosis in cats

Peacock RE, Hosgood G, et al. A randomized, controlled clinical trial of intravenous lipid emulsion as an adjunctive treatment for permethrin toxicosis in cats. J Vet Emerg Crit Care (San Antonio). 2015 Oct;25(5):597-605.

Permethrin is an insecticide commonly used in over-the-counter (and some prescription) flea and tick medications. Despite efficacy in controlling parasites, permethrin (and the related pyrethroids) are toxic to cats; causing tremors, seizures, and potentially death. Treatment is based on the use of anti-seizure medications and muscle relaxants. As permethrin is a fat soluble drug, the use of intravenous lipid emulsion (ILE) to bind the toxin and prevent further seizures has been advocated. The authors of this study investigated the use of lipid emulsion in a series of cats with permethrin toxicosis.

The authors created a staging system for cats with permethrin toxicosis based on video analysis of cats presented for treatment. This resulted in an “A” to “F” system ranging from no clinical signs, through tremors and recumbency, to grand mal seizures. This system may be of great benefit to veterinarians, as it allows for a standardized, objective, and repeatable method to quantify the severity of a common toxicosis.

The study was performed on cats presenting to a group of 13 hospitals for permethrin toxicity. Cats included had permethrin applied by the owner, and there clinically in stage C to F. Clinicians were not blinded to the treatment. ILE treated cats received 15mL/kg over 60 minutes. A bolus of ILE was not performed, as the authors did not consider it beneficial in the absence of potential cardiotoxicity.

Cats were treated with standard protocols including decontamination, diazepam, and methocarbamol. Additional medications were used as needed to control other clinical signs. 14 of the cats received the saline control in addition, and 20 received ILE therapy. There was no difference in average age, gender, breed, weight, or time to presentation between groups. Clinical stages at presentation were statistically identical.

Cats who received ILE therapy returned to stage A or B significantly faster than control cats. ILE cats took an average of 5.5h, where control took 16.5h. There was no statistical difference in duration of hospitalization (27.5h vs 19.4h). No significant side effects were seen in the cats treated with ILE, and no cats died during the course of the study.

The authors do not suggest that ILE be used as a first lien treatment for permethrin toxicosis, as methocarbamol and diazepam are proven to be effective therapies and manage life threatening initial signs. However, ILE therapy appears to decrease the duration of clinical disease, which may theoretically improve prognosis and minimize stress on the animal. (MRK)

See also:
Sutton NM, Bates N, Campbell A. Clinical effects and outcome of feline permethrin spot-on poisonings reported to the Veterinary Poisons Information Service (VPIS), London. J Feline Med Surg. 2007 Aug; 9(4):335-339.

Dymond NL, Swift IM. Permethrin toxicity in cats: a retrospective study of 20 cases. As Vet J. 2008 Jun; 86(6):219-223.