This article reviews permethrin toxicosis and its treatment in cats and incorporates information from pharmacovigilance programs in Australia, the United States, and the United Kingdom. Most incidents of toxicity occurred when owners inappropriately applied canine spot-on products to cats. A smaller number (11%-25%) were affected by being in close contact with recently treated dogs; in 1 case, a cat developed signs of toxicosis after licking an empty permethrin-containing packet. Clinical signs related primarily to the nervous system, including seizures, muscle fasciculations, tremors, shaking, and ataxia. Signs usually developed within a few hours of exposure, with some delayed for 48 hours. Signs resolved or the animal died within 24 to 72 hours. Diagnosis was based primarily on history, clinical examination, and presenting signs. Other than stress-related changes, laboratory values were usually normal. Treatment was directed at treating the signs and was based on control of tremors or seizures, supportive care, and decontamination. Prognosis was good for cats receiving prompt and aggressive treatment. Severely affected cats or those that were not treated (23% in 1 report, 37% in another) died or were euthanized. A review of product labels found them to be adequate. The authors recommend that clients be educated on the importance of reading and following label directions.

COMMENTARY: Despite very prominent warnings on packages, exposure to concentrated permethrin spot-ons meant for dogs continues to be a major toxicosis in cats. Often owners think that a drop or two can be safe despite the warnings; tremors and seizures can occur even with this small exposure. A second, less well known source of exposure is in cats that have close contact (sleeping or grooming) with dogs that have been treated with the products. In the ASPCA Animal Poison Control Center's experience, intravenous methocarbamol remains the treatment of choice because diazepam poorly controls tremors. Bathing the cat with a liquid hand dishwashing detergent (such as Dawn) to remove residual permethrin from the skin and coat is also important but should not be done until the cat's tremors or seizures have been stabilized. Finally, the cat should be kept warm after the bath because hypothermia makes it harder to control tremors.

Permethrin toxicosis in cats. Linnett PJ. AUST VET J 86:32-35, 2008.