Pyrethrin Toxicity in Cats

Extracted from dried flowers of the chrysanthemum family, natural pyrethrins are insect repellents. Both natural pyrethrins and synthetic ones called permethrins are used in insecticides and pet flea and tick products. Natural pyrethrins are broken down by digestive juices, while the liver metabolizes synthetic pyrethrins before they enter an animal's GI tract (see Reference 1).



Pyrethrin toxicity in cats occurs because their livers are incapable of properly metabolizing synthetic pyrethrins (see References 1 and 2).

  1. Types of pyrethrins

    • Insecticides have contained natural pyrethrins for more than a century, says Dr. Holly Nash, DVM. Any of the six different families of them can be present in a pet flea and tick repellent. Most manufacturers, however, label their products as containing nonspecific pyrethrins.

      Many pet care product suppliers prefer synthetic to natural pyrethrins for their stability and extended action. These show up in a wide range of flea and tick repellents, including dips; sprays; spot treatments; shampoos; and flea collars (see Reference 1).

      Both natural and synthetic pyrethrins kill insects by damaging their nervous systems and paralyzing them. Synthetic pyrethrins, however, also interfere with a cat's nervous system (see Reference 3).

    Symptoms of toxicity

    • Although considered extremely safe for cats, natural pyrethrins occasionally cause toxic reactions including excessive salivation, vomiting, tremors, and seizures. Dr. Nash reports that most of these effects will last no more than 24 hours (see Reference 1).

      Symptoms of synthetic pyrethrin toxicity are far more frequent and serious. In 2007, Britain's Veterinary Poisons Information Service reported that nearly 97 percent of 286 cats exposed to a spot flea treatment with the synthetic pyrethrin Permethrin developed symptoms of toxicity.

      These included twitching, tremors and convulsions. The convulsions occurred for an average of 38.9 hours following exposure and the tremors an average of 32 hours. Most of the cats recovered within 72 hours but some needed an entire week, and more than 10 percent of them died (see Resource 1).

    Time Fframe

    • In most cats, symptoms of synthetic pyrethrin toxicity surface between one and three hours after exposure, but can be delayed for as long as 12 hours (see Reference 2, p.3).

    Treatment

    • If you suspect your cat is suffering from exposure to synthetic pyrethrins, get him to your vet as soon as possible.

      Cats exposed to topical forms of synthetic pyrethrins should be thoroughly bathed with mild dish soap and lukewarm water. Overly warm water may enhance absorption of the pyrethrins, worsening the symptoms. For cats with minimal exposure this treatment may be enough.

      If your cat has absorbed lots of synthetic pyrethrins, she may need treatment with an anti-seizure medication like diazepam and/or the anti-tremor medication methocarbynol along with IV fluids to balance her electrolytes.

      Because continuing muscle tremors and seizures can cause heat exhaustion, your pet should have her temperature closely monitored (see Reference 2, p.6).

    Prevention

    • Protect your cat from pyrethrin poisoning by avoiding products with Permethrin or other synthetic pyrethrins. Products labeled for dogs only aren't suitable even at reduced dosages for your cat.

      After treating your dog with a product containing synthetic pyrethrins, avoid accidental exposure by keeping him away from your cat. Always read the labels carefully and follow the instructions exactly with all pest repellents you buy (see Reference 2, pp. 6-7).