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 6 doses) is an over-the-counter medication that works on both cats and dogs up to 25 pounds in weight. (Dogs over 25 pounds can use Capstar for Dogs Only, which costs about $30 for six doses.) It's safe to use on puppies and kittens as young as four weeks old, as long as they weigh at least 2 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. To treat a flea problem fully, Capstar must be combined with another treatment that contains an insect growth regulator (IGR). Novartis, the maker of Capstar, offers another product called Program that could be combined with Capstar to treat all stages of the flea life cycle. However, because of manufacturing issues that shut down a Novartis plant, Program is currently very hard to find, with most retailers showing it as either on backorder or discontinued. 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 reinfested.
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 1,000 owner-written reviews, we found only a handful that mention any problems at all and none that describe serious reactions. Capstar is also effective in most instances; many say they were "shocked" to see how quickly the fleas fell off their pets. Some reviews complain that the product didn't work for them or that its effects only lasted a couple of days, but it's not clear whether these pet owners were using the drug properly. If they gave Capstar by itself and didn't combine it with an IGR, then their pets could easily have become reinfested as new fleas hatched. 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.
We also saw many positive reviews for an oral medication called Comfortis (Est. $95 for 6 doses) . 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 Dogster.com, says it's a great choice for dogs who are prone to skin problems. 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.
Owners generally find Comfortis very effective, with many saying it worked on their pets after other products had failed. However, it's also much more likely to cause negative side effects than Capstar. Vomiting is the most common problem, but some owners report more serious and even life-threatening reactions. 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.