Feline Emergency :: Permethrin Toxicosis

Permethrin is a synthetic type 1 pyrethroid insecticide that is used in an assortment of products from shampoos and sprays to topical canine spot-on products. Many spot-on flea products are available at discount, grocery, and farm stores. Made by various manufacturers, these products have become increasingly popular because of their ease of application and length of efficacy (generally 1 month). Many of these products contain 45-65% permethrin and are labeled for use on dogs only. When applied according to label instructions, spot-on products are generally safe and efficacious. However, when these products are used on animals contrary to those listed on the label instructions, toxicosis may result. Veterinary technicians should be educated about the clinical signs associated with permethrin toxicosis in cats as well as treatment options.

Some pet owners apply spot-on permethrin-containing insecticides on their cats without reading the manufacturer's label, whereas others may read the label but think that a small amount of the product is safe to use. Some cats are exposed to permethrin by coming into contact with dogs that have been treated with a spot-on product. Despite the source of exposure, the end result can be devastating.

Clinical signs - Pyrethroids act by modifying sodium ion channel activity in nerve cells. The resulting nervous excitation causes death in insects. In most mammals, there is generally a rapid metabolic breakdown of pyrethroids by the liver; therefore, no signs of toxicity are likely to occur. Permethrin is detoxicified by ester hydrolysis or oxidation, followed by hepatic hydroxylation and conjugation to either glucuronides or sulfates. Because cats are generally deficient in metabolizing substances through hepatic glucuronidation, they are limited in their ability to metabolize permethrin quickly. Cats will exhibit sensitivity to high concentration of this insecticide. The clinical signs of permethrin toxicosis in cats may include muscle tremors, hyperexcitability, depression, ataxia, vomiting, seizures, anorexia, and death. Signs may develop within a few hours to 3 days following exposure.

Therapy- Treatment of permethrin toxicosis consists of tremor and /or seizure control, dermal decontamination, and supportive care. An attempt should be made to stabilize the patient before starting decontamination. An intravenous catheter should be placed, if possible, to assist in the administration of medications and fluids.

Using diazepam alone usually will not control the seizures. Therefore, the ASPCA-NAPCC recommends the use of intravenous methocarbomal, a centrally acting muscle relaxant, at a dose of 55 to 220 mg/kg. Clinical judgement- based on the severity of the symptoms and the therapeutic response noted - must be used to determine the frequency of administration. One third to one half the dose should be administered as a bolus (not exceeding 2 ml/minute), with the remaining dose given to effect. Methocarbomal doses may be repeated as needed, but should not exceed 330 mg/kg/day. Diazepam, phenobarbitol, pentobarbitol, or isoflurane may be required in conjunction with methocarbomal to achieve optimal seizure control. Phenothiazine tranquilizers should not be used for seizure control because these drugs lower the seizure threshold.

If injectable methocarbomal is not available (i.e., the clinic does not have the injectable product in stock and has been unable to locate a supply from a human pharmacy or other veterinary clinic) and oral administration of the tablet form is not possible (i.e., in the seizuring or vomiting patient), methocarbomal in tablet form may be administered rectally. Because this is an off-label route of administration, its clinical efficacy is not known. This method should be considered only if the injectable route is not available and the oral form cannot be administered successfully. The same dose, starting at the low end, should be used for rectal administration. The tablet should be dissolved in the equivalent of 3 ml of an isotonic solution (i.e., lactated ringer's solution, normal saline), then administered rectally using a urinary catheter.

After the animal has been stabilized, dermal decontamination should be performed. The cat's entire body should be bathed using warm water, and a mild dish detergent (not dishwashing machine detergent), and the cat should then be dried thoroughly using a towel. The animal's body temperature should be monitored and thermoregulation provided as needed. Although hyperthermia is often apparent initially because of increased muscle activity from the tremors and/or seizures, hypothermia may set in later when the muscle activity slows and the animal becomes exhausted. Hypothermia may exacerbate clinical signs and increase recovery time.

Proper supportive care (e.g., administration of intravenous fluids) is essential. Fluids will help maintain hydration and protect the kidney tubules from myogloin buildup, which can occur from muscle damage caused by increased activity. Practitioners should know that atropine, which is commonly used to treat organophosphate insecticide poisoning, is not an antidote for and should not be used to treat permethrin toxicosis. With prompt and agressive treatment, recovery generally can occur within 24-72 hours.

Education is often the key in preventing permethrin toxicosis in cats. Because many flea and tick products are purchased outside the clinic setting, veterinary personnel should help educate pet owners on the importance of reading labels and of using only products specified for the species of their pet. Clients should also be educated about species differences associated with flea and tick products, possible adverse effects of these products, and what to do if their pet shows signs of toxicosis.


Mindy Bough, CVT
Contributing and reviewing authors:
Safdar A. Khan, DVM, MS, PhD, Diplomate of the American Board of Veterinary Toxicology
Michael W. Knight, DVM, Diplomate of the American Board of Veterinary Toxicology and
the American Board of Toxicology
In afilliation with ASPCA-NAPCC, Irbana, IL

See Also:

Just Say No - Hartz pet product dangers (CatHelp-Online)
ASPCA - NAPCCA (National Animal Poison Control Center)
Cats and Flea Control Products - (Cat Fancier's)
(Toxicities associated with flea products in cats)


Products Containing Permethrins:

[X] Denotes products used directly on cats or dogs.
[*] Denotes indoor foggers, premise sprays, and kennel applications.
Please be advised that this list is by no means a complete list of known permethrin-containing products.

* Adams Lawn and Kennel Spay Concentrate
* Adams Room Fogger with Sykillstop
* Breakthru Inverted Aerosol Carpet Spray
* Breakthru Total Release Fogger
X Breakthru with Nylar Spot-On for Dogs
* Daltek QK Total Release Fogger
* Davis Nylar Fogger
X DD-33 Flea and Tick Spray for Dogs and Cats
X Defend Flea and Tick Cream Rinse
* Defend Just-for-homes Fogger plus IGR
X Duocide L.A. Flea & Tick Spray for Dogs and Cats
* Ectiban WP Insecticide Premise Spray
* Ectokyl IGR Total Release Fogger
* Flea Fogger Plus- 7 Month Total Release Fogger
* Grenade ER Premise Insecticide
X Hartz Cat Products- Click HERE
* Interrupt Total Release Fogger
X KC 14-Day Flea & Tick Mist W/Aloe For Dogs & Cats
* Mycodex Environmental Control Aerosol Fogger
X No-Hop Flea and Tick Spray for Dogs and Cats
* Omnitrol IGR Fogger
X Ovi-Spot Plus Topical Flea & Tick Control for Dogs
* Permectrin II- Premise Spray
* Permectrin II- Insecticide For Dogs and Premises
* Permectrin Pet, Yard and Kennel Spray
* Permectrin Pet, Yard, and Kennel Spray Insecticide
X Preventic L.A. Flea & Tick Spray for Dogs
X Proticall Insecticide for Dogs
* Proticall Home Fogger
X Proticall Insecticide Coat Conditioner for Dogs & Cats
X Proticall Permethrin Dip for Dogs
X Prozap Drycide Topical for Pets
X Repel-A-Cide Dip for Dogs and Cats
X Ritter's WB-14 Flea & Tick Spray for Dogs & Cats
X Siphotrol Plus Area Treatment II for Dogs and Premises
* Sungro Permith for Premises
X Synerkyl AQ Pet Spray for Dogs & Cats
X Synerkyl Creme Rinse for Dogs & Cats
X Synerkyl Pet Spray for Dogs & Cats
X Synerkyl Shampoo for Dogs & Cats
* Synerkyl Total Release Indoor Fogger
* Virbac Knockout Flea & Tick Household Spray
* Virbac Knockout Room and Area Fogger
X Virbac Knockout Spray for Dogs


If you suspect your pet may be suffering from a permethrin toxic effect, do not delay, have your pet seen by an emergency veterinary hospital immediately!

CatHelp-Online also wishes to advise you not to use over-the-counter flea and tick products for your kitty, as these products are not only ineffective, but can be dangerous as well. Your vet can prescribe and properly treat your kitty should you be faced with a flea or tick problem. In young kittens, never use flea products unless on the advise of your vet; in kittens less than 10 weeks old, it is best to use only a flea-comb, so please ask your vet for further information.

DO NOT take chances with the health of your kitty by applying canine-specific products on your kitty, and do not rely on others who may say to do so, only your vet is qualified to advise you on proper flea and tick control for your kitty. NEVER use dog parasite control products on kittens or adult kitties. NEVER use a dog parasite control product and dose out small amounts you feel may be safe for a cat or kitten (this ill-conceived advice is frequently given on internet message forums). The problem with this is that the products' manufacturers often modify the ingredients or inert ingredients and concentrations of the product ingredients, making them a greater risk to cats. Online MSDS sheets are not often updated in a timely fashion, making it difficult to determine the exact concentration between product ingredients. Your vet is the ONLY one who can advise you about a safe and effective flea control product for kittens or adult cats, based on your cats' individual health and needs as they apply.

When in doubt, call your vet!


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