Rintu’s history of having received a topical flea product for dogs suggests toxicosis as the cause of his clinical signs. You ask the owners to retrieve the product from home so you can confirm the diagnosis, but you plan to treat the cat for permethrin exposure in the meantime and draw blood for a CBC and serum chemistry profile to rule out other underlying problems.
Pyrethrins are extracted from dried chrysanthemum flowers and are commonly used in insecticides that kill fleas in cats and dogs. Products containing pyrethrins are generally safe and effective in cats and dogs when used according to the label, but toxicosis can occur with overdosing in both species.
Permethrins are synthetic pyrethrins that have a wide margin of safety when used according to the label in dogs but should not be used in cats. Permethrins are fat-soluble compounds that undergo rapid metabolism and excretion after oral or dermal absorption, and clinical signs of toxicosis can last two or three days.
Permethrins interfere with sodium channels in nerve endings and alter activation of the action potential and result in repetitive nerve firing.
A diagnosis of permethrin toxicosis is based primarily on a history of exposure and supportive clinical signs; in vivo testing is not available.