Permethrin, a synthetic type I pyrethroid, is found in many flea and tick shampoos, dips, foggers, spot-ons, and sprays as
well as many household and yard insecticide formulations. While permethrins have a relatively wide margin of safety in dogs,
cats appear to be more sensitive to the toxicity of concentrated permethrins. The low-concentration products (sprays, foggers)
approved for use on cats contain 0.05–0.1% permethrin and do not cause the clinical syndrome that has been associated with
the inappropriate use of concentrated (45–65% permethrin) spot-on products on cats. Permethrin toxicity usually occurs when
the concentrated dog product is applied to cats, but cats that actively groom or engage in close physical contact with recently
treated dogs may also be at risk of toxicity.
Clinical signs of permethrin toxicosis in cats include hypersalivation, depression, ear twitching, facial twitching, generalized
muscle tremors or fasciculations, hyperthermia, vomiting, anorexia, seizures, and possibly death. The onset of clinical signs
is usually within a few hours of exposure but may be delayed up to 24 hours. The severity of clinical signs often varies among
Treatment of permethrin toxicosis should include control of tremors, supportive care, and decontamination. Methocarbamol (50–150
mg/kg slow IV; do not exceed 330 mg/kg/day) is preferred to control the tremors. If no injectable methocarbamol is available,
the oral form may be dissolved in water and administered rectally. If the cat is actively seizing, barbiturates or inhalant
anesthesia may be needed. Given alone, diazepam may actually exacerbate the tremors, but once methocarbamol has been used
to reduce the tremor activity, diazepam is sometimes useful at reducing hyperesthesia. The use of atropine is not indicated
in pyrethroid exposures and should be avoided.
Once tremors are under control, cats should be bathed to remove the product from the haircoat and skin. Liquid dishwashing
soap (e.g. Dawn®) should be used to bathe the entire cat. Thermoregulation is very important in these cases, as tremoring
cats often present hyperthermic only to develop hypothermia following tremor control and bathing. Hypothermic cats may experience
recrudescence of tremors as well as decreased metabolism of the permethrin due to decreased metabolic rate. Permethrins appear
to have no direct action on the liver or kidneys, but fluids may be helpful in protecting the kidneys from myoglobin breakdown
products in severely tremoring or seizing cats. Potential complications to permethrin toxicosis in cats include disseminated
intravascular coagulopathy and rhabdomyolysis due to prolonged seizure activity and/or hyperthermia. The prognosis for mildly
tremoring cats is usually good, but treatment may be required for up to 24–48 hours. The prognosis for severely seizuring
cats is guarded, although many of these will make full recoveries if given aggressive veterinary care.
Phenothrin is another synthetic type I pyrethroid. A formulation containing 85.7% phenothrin has been approved for use on
cats. Most cats tolerate phenothrin, but a small percentage of cats will develop signs similar to permethrin toxicosis after
administration of the product per label directions. Usually the signs from phenothrin toxicosis in cats are milder and do
not last as long as permethrin toxicosis. In rare instances severe signs may be seen. The clinical signs and management of
phenothrin toxicosis in cats is the same as for permethrin toxicosis. The prognosis for phenothrin toxicosis is generally
quite good. Adverse reactions to products that have been used appropriately (per label) should be reported back to the manufacturer
and/or appropriate government regulatory agency. Adverse reactions to appropriately used pesticides may be reported to the
EPA via the National Pesticide Information Center (NPIC) at 1-800-858-7378.