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Capstar for Dogs and Cats Review

By: Carl Laron on April 24, 2018

Bottom Line

Capstar for Dogs and Cats is an over-the-counter tablet that's very safe for both dogs and cats as young as four weeks and that weigh between 2 and 25 pounds. A version for dogs over 25 pounds is also available. Capstar kills fleas quickly and without the mess of topical treatments, but it works only on adult fleas.


  • Kills adult fleas quickly
  • Side effects are rare
  • No mess
  • No prescription required


  • Doesn't kill flea eggs or larvae
  • Pets may not take pill willingly
Our Analysis
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Breaking it down


Kills adult fleas only. Most reviewers, including vets and pet owners, say Capstar for Dogs and Cats works amazingly fast. Many users say they could literally see fleas dropping off their pets in an hour or less. However, others complain that it had no effect on their pets or that it wore off very quickly. Some of these owners may not have realized that Capstar kills only adult fleas and won't stop new ones from appearing. Some owners say they can keep fleas at bay just by repeating the dose of Capstar every week or so, but others use Capstar for immediate relief and a topical treatment for long-term control.


Safe for pets and humans. All reviewers agree that Capstar poses virtually no risk to humans. Side effects in pets are also less common, and less severe, than with topical treatments. A few owners note that pets (especially cats) may become hyperactive as the medicine takes effect, possibly because the fleas bite more as they die. Rare -- but not unheard of -- side effects include lethargy, trembling and allergic reactions. As with virtually all flea treatments, pet owners should keep an eye on their animals after administering Capstar.

Ease of use

Can be tricky to administer. Some pet owners like the fact that this tablet doesn't create any mess like topical treatments do. Most users report no problems getting their pets to take Capstar, but a few say that some pets, especially cats, are reluctant to swallow it. Some owners say the easiest method is to put the pill in the pet's food or hide it in a treat such as cheese or peanut butter.

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