Felis ISSN 2398-2950

Pyrethroid toxicosis

Contributor(s): Nicola Bates, Rosalind Dalefield


  • Pyrethrins Pyrethrins are naturally insecticides derived from Chrysanthemum plants.
  • Pyrethroids are synthetic analogues with greater stability and potency.
  • Examples of specific compounds include:
    • Allethrin
    • Alphacypermethrin
    • Bifenthrin
    • Bioallethrin
    • Cypermethrin
    • Deltamethrin
    • Fenvalerate
    • Fluvalinate
    • Flucythrinate
    • Fluorocyphenomethrin
    • Permethrin Permethrin 
    • Phenothrin
    • Resmethrin
    • Tetramethrin
    • Transfluthrin.
  • Pyrethrins and pyrethroids are commonly used insecticides.
  • Cause:dermal absorption or ingestion of insecticide, including ingestion of product groomed off the fur following treatment for external parasites.
  • Action:alteration of the sodium ion channels of nerves.
  • Signs:may be neurotoxic reaction or allergic reaction.
  • Treatment:symptomatic, may need to be intensive and prolonged.
  • Prognosis:generally favorable with early, aggressive treatment, but guarded in cats with severe seizures.



  • Overdose or special sensitivity to pyrethrin or pyrethroid insecticide.
  • Permethrin toxicity is a common poisoning in cats.

Predisposing factors


  • Application or administration of excessive amount of insecticide.
  • Use on cats of a permethrin-containing product formulated for dogs.
  • Accidental oral administration of a canine spot-on preparation.
  • Genetic hypersusceptibility to pyrethrins/pyrethroids.
  • Allergic sensitivity to pyrethrins/pyrethroids.


  • Rapid absorption.
  • May be overdose or special sensitivity.
  • May be neurotoxic (common) or allergic response.
  • Neurotoxic mechanism is interference with sodium channel function.
  • The feline liver is relatively inefficient at glucuronide conjugation leading to slow excretion and accumulation of metabolites.
  • Allergic reaction generally dermal and nonfatal although there may be severe self-trauma.
    • Allergic reaction may escalate to anaphylactic reaction which is acutely life-threatening.
  • Prolonged sodium conductance into nerve fibers    →   increased length of action potential   →   repetitive nerve firing.
  • Neurotoxicity with twitching, muscle tremors, hyperthermia and seizures.
  • Allergic reactions which may result from minimal or appropriate exposure include:
    • Urticaria.
    • Hyperemic skin.
    • Pruritis.
  • Anaphylaxis Anaphylaxis includes:
    • Dyspnea.
    • Circulatory collapse.
    • Sudden death.


  • Onset may be within a few hours or up to 36 hours.
  • Full recovery from neurotoxicosis usually occurs within 24 to 72 hours, but can be longer.
  • Recovering cats may show prolonged inappetence.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • DeGroot W D (2014) Intravenous lipid emulsion for treating permethrin toxicoisis in  a cat. Can Vet J 55 (1), 1253-1254 PubMed.
  • Draper W E, Bolfer L, Cottam E et al (2013) Methocarbamol CRI for symptomatic treatment of pyrethroid intoxication: a report of three cases. JAAHA 49 (5), 325-328 PubMed.
  • Kuo K, Odunayo A (2013) Adjunctive therapy with intravenous lipid emulsion and methocarbamol for permethrin toxicity in 2 cats. J Vet Emerg Crit Care 23 (4), 436-441 PubMed.
  • Muentener C R, Spicher C, Page S W (2013) Treating permethrin poisoning in cats. Vet Rec 172 (24), 643 PubMed.
  • Peacock R E, Hosgood G, Swindells K L et al (2013) A randomised controlled clinical trial of an intravenous lipid emulsion for the treatment of permethrin toxicosis in cats. J Vet Emerg Crit Care 25 (5), 597-605 VetMedResource.
  • Brückner M, Schwedes C S (2012) Successful treatment of permethrin toxicosis in two cats with an intravenous lipid administration. Tierarztl Prax Ausg K Kleintiere Heimtiere 40 (2), 129-134 PubMed.
  • Boland L A & Angles J M (2010) Feline permethrin toxicity: retrospective study of 42 cases. J Feline Med Surg 12 (2), 61-71 PubMed.
  • Malik R, Ward M P, Seavers A et al (2010) Permethrin spot-on intoxication of cats. Literature review and survey of veterinary practitioners in Australia.​ J Feline Med Surg 12 (1), 5-14 PubMed.
  • Linnett P J (2008) Permethrin toxixcosis in cats. Aust Vet J 86 (1-2), 32-35 PubMed.
  • Sutton N M, Bates N & Campbell A (2007) Clinical effects and outcome of feline permethrin spot-on poisonings reported to the Veterinary Poisons Information Service (VPIS), London. J Feline Med Surg (4), 335-339 PubMed.

Other sources of information

  • Khan S A (2013) Pyrethrins and Pyrethroids. In: Small Animal Toxicology, 3rd edn, Peterson M E and Talcott  P A (eds), Elsevier, St Louis, Missouri, pp 769-775.
  • Gruber N M (2011) Permethrins and Pyethroids. In: Osweiler G D, Hovda L R, Brutlag A G, Lee J A (eds)Blackwell's Five Minute Veterinary Consult Clinical Companion. Small Animal Toxicology.Wiley-Blackwell, Ames, Iowa, pp 636-643.