Toxic Effects of Flea Medication

EPA Responsibility

• The U.S. Environmental Protection Agency says it is developing more strict evaluation plans for products in hopes of reducing adverse side effects in animals as of 2010. The EPA says it plans to tighten regulation by requiring pre-market clinical trials, post-market surveillance and mandatory reporting of any adverse side effects.

  The EPA says it is also working to ensure labels read clearly on medications to avoid dosage issues and confusion between cat and dog products, as well as to clarify that inactive "inert" ingredients can contribute to the toxicity of the product.

Consumer Responsibility

• Although the EPA is an important regulator, the consumer must also research products. Some products are designed specifically for dogs and can harm cats. Some products work once and instantly, with others offering ongoing protection. Different components target different stages of the flea life cycle, such as eggs or adult fleas. Products are administered as a collar, spray, cream or pill. Finally, some products protect against parasites in addition to fleas, such as ticks, heartworm and ear mites.

  Along with researching, communicating clearly with your veterinarian is also a must. As with any drug cocktail for humans, animals can also exhibit adverse reactions when mixing certain diets, medications and supplements.

Fipronil

• Fipronil is a pesticide that attacks the central nervous system of insects and an active ingredient in commercially available flea and tick applications. Although the EPA classified fipronil as a "possible human carcinogen," the National Pesticide Information Center has cited studies showing that feeding fipronil to rats for two years caused thyroid tumors, increased seizure rate and death. A consumer alert by the Animal Protection of New Mexico reported fipronil can cause thyroid damage, increased organ weight, loss of appetite, convulsions, barking, crying, unsteady gait, labored breathing, reduced fertility, chemical burn and hair loss in dogs.

Imidacloprid

• Imidacloprid is an insecticide modeled after the structure of nicotine and an active ingredient in several flea applications. A consumer alert by the Animal Protection of New Mexico reported imidacloprid can cause damage to the liver, kidney, thyroid, heart, lungs, spleen, gonads and brain in dogs. Also, it can lead to increased cholesterol, incoordination, labored breathing, increased miscarriages and smaller offspring.

Methoprene

• Methoprene is another component of some flea applications, is a mostly nontoxic insect growth regulator. This means that it prevents larvae from developing into adult insects (and is highly toxic to adult insects.) Scientific studies found increased liver weights in experimental rats, as reported by the Extension Toxicology Network. Dogs' bodies reportedly break down methoprene and excrete it safely.

Permethrin

• Permethrin is an insecticide that causes paralysis and death in insects. Permethrin is less harmful to dogs than cats due to their larger body size and greater metabolic capabilities. The National Pesticide Information Center reported that in one study of 11 cats treated with permethrin, all exhibited adverse side effects, including seizures, incoordination and agitation. All of the cats were hospitalized, and four died. Additionally, one study showed that a cat showed the same adverse effects after being near a dog that had been treated with permethrin.

Alternatives

• Some alternatives to these medications can include bathing and combing animals more frequently, herbal sprays and safer chemicals such as Nylar. Contact your veterinarian for additional information, and always research products thoroughly.