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Capstar Flea Treatment Side Effects

Side Effects and Risks Associated with CAPSTAR Treatment


Fleas are a nuisance to any pet and pet owner; so it's important to find an effective flea treatment that works quickly. There are a wide variety of flea treatments and preventives out there for pets, so it can be difficult to find the right treatment for you and your pet. Households with both cats and dogs can face additional difficulty in finding a treatment that is sensitive for cats but still strong enough to eliminate infestations on dogs.

Capstar Flea Control tablets are among the fastest-acting flea control solutions on the market. It is available in multiple formulations to treat all dogs and cats that are over one month old and over 2 pounds. Capstar comes in an easy-to-administer tablet and begins killing fleas within the first 30 minutes of its administration to provide fast-acting relief1.

Capstar can be used in conjunction with preventive treatments to provide comprehensive protection against fleas. There is, however, a risk that combining Capstar with other medications and treatments may lead to other adverse effects.

flea aging and a dog scratching itself

Pros and Cons of Using Capstar

  • Kills adult fleas within half an hour
  • Works for all cats and dogs over a month old and 2 lbs
  • Works for pregnant or lactating pets.
  • Less expensive than other tablets
  • Comprehensive flea treatment regimen for cats and dogs
  • Can be utilized as a preventive medicine to give protection against fleas (valuable in the cases of kenneling, pet shows and traveling)
  • Can be administered as often as once daily to eliminate fleas in the case of re-infestation
  • If you miss a dose or are uncertain the dose was given, a second pill might be given safely

Side Effects

Capstar is known to cause certain side effects with regular use, whereas other adverse reactions may be the result of inappropriate usage. Side effects also differ depending on which animal is being treated, as dogs and cats have different reactions to the treatment.

It is really important to mention that, even though this 'side effects' area mentions many frightful aggressive reactions that may be linked to Capstar flea medicine, in actuality, such reactions are exceedingly uncommon.

cat and dog researching side effectsCapstar Side Effects for Both Cats & Dogs
  • Lethargy
  • Vomiting
  • Itching
  • Inappetence
  • Decreased Appetite
  • Diarrhea
  • Hyperactivity
  • Incoordination
  • Trembling
  • Seizures
  • Panting
  • Vocalization
  • Salivation
  • Fever
  • Nervousness
Capstar Side Effects for Cats
  • Difficulty Breathing
  • Pupil Dilation
  • Increased Heart Rate

Cats taking Capstar may experience many of the same side effects as dogs. Other side effects that cats may exhibit include pupil dilation, increased heart rate, vocalization, fever, and salivation.

Capstar Side Effects for Dogs
  • Depression
  • Allergic Reactions Including Hives

The most common side effects that affect dogs include lethargy or hyperactivity, incoordination and trembling or seizures, and nervousness. Dogs may also experience excessive panting, vomiting, itching, inappetence, and diarrhea.

Taking a look at the dose range for Capstar pills should give you an idea of the medication's safety. Cats and dogs are dosed with Capstar flea drug at a dosage of 1mg/kg orally. A 25-pound dog is roughly 11.4 kg and gets an 11.4 mg dose of Capstar. An entire 11.4 mg tablet will be enough for animals weighing between 1 kg to 11.36 kg. The 1kg animal is getting a dose that is 11.4 times that of the 11.36kg animal but then it isn't harmful, and thus demonstrates that Capstar flea drug has an outgoing safety range.

How Does It Work?

Capstar flea control pills are completely absorbed in the intestinal tract during dosing. Following oral dosing, drug levels will immensely reach in the animal's blood after around 40 minutes in cats and 80 minutes in dogs.


After your pet takes the Capstar tablet, the Nitenpyram is immersed into the bloodstream very quickly. The minute a flea takes a blood meal from your pet, they ingest enough of the drug to kill them. Because they don't take a blood meal, it does not work on young fleas, larvae, or eggs1.

Nitenpyram is white and yellow and is the active ingredient in Capstar and is an over the counter drug. In case you're searching for a fast and abrupt fix to those annoying flea issues then Capstar is the best solution for you and your pet. Capstar has a gentle smell but the smell not at all poisonous. Capstar flea control pills are insoluble in water, implying that they won't break down to form a homogenous solution. Nitenpyram is chemically stable under normal conditions of storage.

Nitenpyram is a neonicotinoid, which means it is similar to pesticide nicotine. It acts on the flea central nervous system by fastening to acetylcholine receptors. Acetylcholine is a vital neurotransmitter, and a barrier of the receptor interferes with the passage of nerve signals and leads to the eradication of the fleas' central nervous system.

Dog scratching itself

Precautions to Take When Using Capstar

You should buy tablets that are right according to the weight of your dog or cat. Try not to divide big tablets into two to offer it to puppies. All cats and dogs in the family unit ought to be treated within the same time with Capstar flea control. This is because untreated pets can go about as a storage house for the fleas. Treatment should start—whether in late winter or early spring—towards the beginning of the flea season. Treatment can begin whenever fleas are seen on your pet.

Be vigilant, readers! Pets will frequently hint about a disturbance for up to 7 hours after Capstar treatment is given. This specific and regular type of disturbance is described by such signs:

  • Scratching
  • Biting the fur
  • Licking the fur
  • Skin twitching
Vocalization, hyperactivity and panting may likewise be seen. This type of response isn't commonly a consequence of the medication, yet a reaction to the quick demise of fleas. The fleas become momentarily 'energized' and begin to twitch as the Nitenpyram poison sets in, making peculiar, conceivably sensitive sensations against the cat or dog's skin. A recent report in the Journal of Medical Entomology affirms and depicts these responses. It can increase in "scratching, panting, licking and twitching" symptoms in the first 5 hours after Capstar ingestion; with panting and licking proceeding to 7 hours after the medication was first dosed.

Alternative Medications to Capstar

K9 Advantix II

For solutions that offer protection against these additional pests, you can look to other solutions such as K9 Advantix II for dogs, or, for an applicator approach, Frontline Plus for cats and dogs. Both topical solutions offer up to one month of protection against fleas and more. They also come in different formulations to ensure that you can find the proper dosage for your dog or cat based on their weight.

You can also use Seresto Flea & Tick Collars for a collar approach. It kills fleas and ticks within 6 hours and protects your pet for up to 8 months. Check out our 10 Best Flea Treatments for Dogs & Cats page if you're still unsure about Capstar!

We hope this article has helped inform you of the advantages and risks associated with Capstar and possible alternatives to this treatment so that you can find the perfect product for your pets!

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