Capstar is a tablet that contains nitenpyram, and a single dose should kill all of the adult fleas on your dog or cat in 24 hours. Capstar enters a dog or cat's bloodstream in about 20 minutes, and it is ingested by biting fleas and kills them. Because it is not a monthly medicine, like many topical treatments, Capstar can be given only when needed. It is ideal for use when a pet is more likely to be exposed to other animals with fleas, such as when boarded or at pet shows.

On the Other: It Has Its Downsides

Only about 15 percent of the fleas on a pet are adults. Capstar does not kill immature fleas, or nits, which can still develop into adults. It also must be administered in tablet form. Unlike topical medicines, such as Frontline, Capstar is not simply placed between your pet's shoulder blades. If you have trouble giving your pet oral medicines, Capstar can be problematic.

Bottom Line

Capstar is good for killing adult fleas but must be used in combination with other flea medicines if you want to prevent fleas and kill both adults and nits. Because it is typically much cheaper than monthly medicines, Capstar is ideal if you want to get rid of adult fleas that might have been transferred to your pet from another animal or if your pet has flea allergies. Monthly medicines take longer to act, so your allergic pet will suffer severe itching and discomfort longer than if treated with Capstar.

Source:

How Capstar Works

Capstar Review

Fleas on Dogs and Cats