Best Flea Medications

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Capstar for Dogs and Cats Review
Best Reviewed

Best flea medication

Capstar for Dogs and Cats

Oral treatments kill adult fleas only

For pet owners who find topical treatments messy or inconvenient, medications in tablet form can be a simpler solution to a flea problem. Capstar for Dogs and Cats (Est. $25 for six doses) is an over-the-counter medication that works on both cats and dogs between two and 25 pounds in weight. Capstar for Dogs (Est. $25 for six doses) is the same product but in a higher dosage and is intended for dogs over 25 pounds.

The active ingredient in Capstar, nitenpyram, works very quickly, killing adult fleas in as little as 30 minutes. This means Capstar can provide quick relief for pets with flea allergies. What it can't do, however, is kill flea eggs and larvae. But Capstar can safely be given as often as once per day, so pet owners have the option of repeating the dose if their pets are re-infested.

Since Capstar is a pill, it poses virtually no risk to humans who use it. Side effects in pets are also very rare. In more than 4,000 owner-written reviews across sites such as and, we found only a couple that mention any serious reactions. Some owners do complain that the product didn't work for their animal or that its effects only lasted a couple of days. Another problem some users have is getting their pets to take the pill. According to reviews, dogs will usually take the pill if it's tucked into a treat like peanut butter or cheese, but cats may be more reluctant to swallow it. However, most say that Capstar is very effective; many say they were "shocked" to see how quickly the fleas fell off their pets.

We also saw many positive reviews for an oral medication called Comfortis (Est. $85 and up for six doses). Like Capstar, Comfortis works only on adult fleas, but its effects last a full month, so vets say it will continue to kill new fleas as they develop. Unlike Capstar, Comfortis is available only with a prescription from a vet, and it can only be given to pets at least 14 weeks old.

Veterinarians tend to be enthusiastic about this treatment. The vets at Twin Maples Veterinary Hospital in West Carrollton, Ohio, praise its ease of use, while vet Eric Barchas, writing for, says it's a great choice for dogs who are prone to skin problems. Owners generally find Comfortis very effective as well, with many saying it worked on their pets after other products had failed. At it earns a 4.5-star rating following more than 1,070 reviews.

However, Comfortis is also much more likely to cause negative side effects than Capstar. Vomiting is the most common problem, and Barchas admits that "a small proportion" of dogs will be unable to use Comfortis for this reason. The reviews we consulted from users included rare reports of more serious side effects as well. Dogs are more likely to develop those side effects than cats. Comfortis must be administered exactly as directed, and it can also interact badly with certain other medications, including ivermectin, which is used in most treatments for heartworm. The manufacturer advises pet owners to use this product only under the guidance and supervision of a veterinarian.

Most pet owners find Comfortis easy to use. Users like the fact that, unlike topical treatments, it doesn't have any odor or leave a greasy residue on the pet's fur. However, a few pet owners say getting the pet to take the pill can be tricky. Some users say their pets ate the beef-flavored tablet right out of their (the owners') hands, but others say they had to resort to tricks like slipping it in a "pill pocket" or grinding it up and mixing it with peanut butter.

If getting your dog -- and only your dog, as it's not suitable for cats -- to take their flea medication is a challenge, Nexgard (Est. $60 for three doses) could be the solution. These chewable tablets, available by prescription only, are beef flavored and eagerly gobbled up by dogs. It's relatively new, but is already garnering good feedback from users. Side effects are not unheard of but seem to be relatively rare. Vets so far are reporting good results as well. Dr. Thomas B. McMillen at the Mercy Animal Hospital in Cranston, R.I., calls it "Probably our favorite at the current time."

Capstar Flea Tablets for Dogs and Cats, 6 Count, 2-25 lbs, Blue
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Capstar for Dogs over 25 lbs 6 tablets GREEN
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