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The Dangers Of Over The Counter Flea Medication - Tsawwassen Animal Hospital

The Dangers Of Over The Counter Flea Medication


Education Director, Veterinary Partner.com

Over-the-Counter Flea Products: Biospot,  Control,  Defend Exspot

Ten years ago, we were controlling fleas the old fashioned way: fogging and spraying the house, powdering, spraying and shampooing the pets. The pets hated it. It smelled funny. It was hard work and yet it hardly worked.

We look back and barely remember all that now. Today we can give a Capstar pill and rid a pet of fleas within an hour or so. We can apply oils behind a pet’s neck and achieve 30 days of flea protection. The spread of these new generation long-acting topical flea products has brought flea control to a new level of both convenience and effectiveness. And there are many of these topicals to choose from; in fact, sometimes it seems like every year there is a new one.

Many people do not realize that these are not simply different brands of the same product. In reality, the prescription flea topicals are totally different from the over-the-counter ones and completely different from each other. (For details see a flea product comparison.) It is the over-the-counter products that are largely the same and it is important to know when it might be a good idea to buy them and when it would be a waste of money.

How It Started

Going back to the days before the new generation products, there was one product that stood out among the sprays, foams, powders, and shampoos. It was the first product that could dissolve in a dog’s skin oils and thus spread in the oil film all over a dog’s skin surface. A single application lasted for about a month. This product was called Defend Exspot and is still available today. At that time, however, it seemed like a miracle. Its ability to spread in skin oil by itself was termed “translocation” and was due to the chemical properties of its active ingredient: “permethrin”.

What is Permethrin?

For hundreds of years insects have been controlled by using extracts from pyrethrum flowers. These natural insecticides, called “pyrethrins”, were highly effective and are still widely used today. Still, one of the problems with them was that they were very short-acting and could not deliver sustained insect killing power. Scientists began modifying pyrethrins and developed many pyrethrin versions that could last for long time periods. The pyrethrin derivatives are called pyrethroids. They are easily identified on a product label by their “ethrin” suffix. Common examples include: resmethrin, allethrin, and, of course, permethrin.

The permethrin based topical products offered many advantages:

  • Relative low cost compared to prescription products
  • Excellent tick protection as well as flea control
  • Some mosquito repellent properties
  • Ability to be combined with other insecticides without toxicity fears
  • Availability at most pet supply outlets

But there were some problems as well:

  • The high concentrations of permethrin needed for the translocation effect are extremely toxic to cats. This created not only a marketing problem but a health issue for families with both dogs and cats.
  • Permethrin is not waterproof. Bathing or swimming will wash it off.
  • Permethrin has been in use for over 20 years and many flea populations are resistant to it. This manifests as the product seeming to last only 2-3 weeks instead of the full 4 weeks. In many homes, permethrin has virtually no flea killing ability at all.

It was no wonder that the advent of Bayer’s Advantage all but captured the market with its introduction in 1946. Advantage boasted a huge safety margin, a feline version, and, because It was a new insecticide, virtually no flea resistance. Advantage also had a major pharmaceutical company to promote it and even with Defend Exspot slashing its price, it was rapidly eclipsed.

Advantage was soon followed by Frontline and Revolution, all three products being sold only through veterinarians. Public demand was high and low cost sources were sought, opening up a black market supplying pet stores. Manufacturers of the permethrin products saw an opening and began to mimic the packaging of the prescription products, suggesting but never actually claiming to be a generic version of the same thing.

BioSpot is introduced

BioSpot and another product called Breakthrough were the next permethrin products to emerge. For extra efficacy, they added an “insect growth regulator” to their formula which serves to sterilize any fleas surviving the permethrin exposure. The sterilizer helps to keep resistant fleas from reproducing but has no flea-killing activity on its own. A non-toxic chemical caller “methoprene” was initially used by BioSpot. Currently, BioSpot uses a newer insect growth regular called Nylar but the principle is the same. Hartz soon introduced Control which also contains permethrin plus an insect growth regulator. These products are readily available in pet stores, grocery stores, anywhere that sells pet supplies. The newest permethrin product (this one without an insect growth regulator) Is Kiltix, introduced by Bayer to supplement Advantage, which has no tick control properties on its own.

Example of Over The Counter Flea Medications

  • Biospot
  • Hartz Care for dog and puppies
  • Hartz_Care for cats and kittens
  • Kiltix

Should You Use a Permethrin Product a Your Dog?

The bottom line for this decision involves weighing the pros and cons already listed.

  • If you are planning to use a permethrin product for flea control, weigh the low price against the resistance level of the fleas in your home. After some 20 years of permethrin use, these products are not reliable for flea control. If they work for you, terrific. If not, a better product is probably worth the extra money.
  • Absolutely do not use these products in cats or on a dog that regularly snuggles up to a cat! These products use far too high a concentration of permethrin for cats.
  • Permethrin products excel when it comes to tick control. You may want to use a prescription product for fleas and combine it with a permethrin product for ticks. Permethrinn products are compatible with all the prescription topicals and orals.

If you are not sure what to use or what is compatible with what, always ask your veterinarian.

At the Tsawwassen Animal Hospital we do not recommend using permethrin-containing products with the exception of specific cases of dogs needing tick control.  We have seen too many heart-breaking cases of cats that have been accidentally dosed or have come in contact with treated dogs and died. We have excellent, safer flea control products such as Advantage, Program and Revolution as well as the very safe quick kill product Capstar.  If you have questions or would like more information please do not hesitate to call us at 604-943-9385

Dr. Tina Gemeinhardt

Neurology Case Studies

Permethrin Toxicity in a Cat

Tabitha Thompson, DVM

A 3 yr. old MC DSH affected by canine permethrin Flea control

Product. This was taken after his severe seizures and tremors were controlled with several doses of IV

Methocarbamol, bathing with Dawn dish detergent, and placing IV catheter for fluid

Administration. Note that the cat is still experiencing uncontrollable twitching most obviously seen in the face and tail. Another cat in the same household that had the same product applied was less severely affected.

Date Published; April 24, 2003

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