What is Activyl For Cats?

Cat Meds

If you’ve ever had a cat infested with fleas, you know the intense suffering fleas inflict. They may scratch themselves raw to the point of loosing their fur. That along with the constant itching, crying out and inflammation is a sign of Ctenocephalides felis, or common cat flea infestation. Fleas are parasites that feed off oanimal or human blood. While they have no wings, they can and do jump from host to host, enjoying a swig of fresh blood when they land. Even though there are over 2500 species of fleas, when your cat or dog become infested it’s probably Ctenocephalides felis. Prolific breeders, the average flea can pump out around 40 to 50 eggs per day with their young residing in carpeting, curtains and bedding, only coming out to feed. However, as tough as fleas are, there’s a new sheriff in town: Activyl.

Signs of Flea Infestation

When a flea bites and pierces the skin of your cat, their salivary glands will emit a substance which will cause constant itching and redness. This is known as FAD or flea allergy dermatitis. Not only does the hypersensitivity to flea saliva cause pain and discomfort, fleas can also infect your pet with diseases such as typhus or bar-tonellosis. Not only that, if a flea is carrying a tapeworm, the tapeworm may infect your cat if the cat happens to ingest that flea during cleaning. If you notice your cat is scratching more than usual, it’s time to search them for fleas. You can do this by physically looking through their fur or by purchasing an inexpensive flea comb. Flea combs will pick up the fleas as you run it through your cats fur. Other evidence of flea infestation is called flea dirt. Flea dirt resembles black specks in your cats fur. So check your cats fur or bedding for these left-over specks. If you notice any of these signs, it’s time to get serious. Though you can take your cat to the vet for a flea bath and meds, you can also opt for the more convenient and cost effective approach and purchase Activyl for cats.

What is Activyl?

Activyl is a flea treatment developed and sold by Intervet/Merck Animal Health. This treatment is applied topically to the cat or kitten once a month. The main ingredient is indoxacarb. Indoxacarb works by halting the movement of sodium ions to the fleas nerve cells. As a result, the flea finds that it can no longer feed on blood, becomes paralyzed and dies. This is the perfect solution when it comes to ridding your home of fleas as it considers the fleas life cycle for that month.


As established, Activyl’s active ingredient is indoxacarb. Developed by DuPont, indoxacarb is a pesticide used in a variety of products designed to kill roaches, ants and other insect pests. Indoxacarb works via a process called bioactivation. In Activyl, indoxacarb is bioactivated inside the flea itself by way of by enzymatic N-decarbomethoxylation. This bioactivation means that once it comes in contact with the flea it transforms into a insecticidal metabolite. In other words indoxacarb becomes activated using the fleas enzymes. This bioactivation is insect specific only and does not interfere with mammalian processes. When indoxacarb comes in contact with mammalian systems, the indoxacarb is transformed into non-toxic metabolites. When you apply Activyl to your cats fur, Activyl begins to blend with the skins naturally occurring oils and diffuses through the fur. When an unsuspecting flea jumps onto your cat for a quick snack, it immediately comes into contact with Activyl. Once contact is achieved, the flea absorbs Activyl. This means extra comfort for your cat, as the flea doesn’t have to bite your pet in order to get the Activyl into their system. Here, indoxacarb transforms into a toxin designed to kill the flea. Once bioactivation occurs, fleas can’t eat, develop paralysis and die after 8 to 12 hours. Activyl also eliminates the eggs and larvae. By doing so it halts the fleas lifecycle. This is important, because if you don’t interfere with their lifecycle, you will not end the infestation of pet or home.

How to Use Activyl

Activyl by Merck comes in two dosage sizes: Large cats that weigh 9 or more pounds, and small cats which weigh 2 to 9 pounds. Each dosage size comes in a tube. Locate the area near the base of your cats skull. Begin by parting the fur, exposing the skin. Pick up the tube of Activyl, place the tip of the tube on the exposed skin and squeeze the entire tube onto the skin. Your cat can be in a lying position or standing for application, whichever is easier for you. Important: ALL pets in your home must be treated for fleas, or you risk being reinfected.


Please read the instructions which come with your supply of Activyl completely before application. It’s crucial that you are made aware of the restrictions when it comes to applying Activyl to your cat.

  • For external use only
  • Use on cats only. Never apply to any other animal or human
  • Never use this product on male or female cats you will be breeding. Never use on nursing or pregnant cats
  • Assume nothing. Read the directions completely before starting
  • Follow directions. Do not deviate from them
  • Do not use on cats or kittens below the age of 8 weeks or cats under 9 pounds
  • Consult your vet before giving Activyl to an older cat
  • Steer clear of the treated area. Under no circumstances allow children to pet the cat or kitten until the area of application is completely dry
  • One application per month not more
  • Under no circumstances allow children to handle this product

Side Effects

After you’ve applied the Activyl keep an eye on your cat or kitten for side effects. If you do notice a side effect(s) then please take your pet to the vet right away. Things to watch out for include:

  • Excessive salivation which is the result of ingesting the product
  • Redness and scratching at the site of application
  • Shaking, having trouble balancing, and convulsions
  • Dilated pupils, trouble seeing
  • Vomiting
  • Weakness or hyperactivity

Final Thoughts

When your pet becomes infested with fleas, it becomes their living nightmare. When those fleas infest your home then you share in that nightmare. Ridding your pet of fleas is not as easy as it looks. It’s not uncommon for fleas to develop a resistance to anti-flea products like shampoos and powders. That’s where Activyl comes in. It’s main ingredient indoxacarb is meant to defeat this resistance, ensuring that the medication will continue to kill fleas without the fleas becoming resistant to the medication. Since application is only once per month, using it is a simple affair. Again, you are responsible for reading the instructions before application. Also make yourself knowledgeable to the restrictions and side effects of this product.

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