What to Know About Nitenpyram (Capstar) Side Effects in Dogs and Cats

Nitenpyram, sold under the brand name Capstar, effectively rids your pet of fleas for the short term -- up to 48 hours. It's not a substitute for a monthly topical or oral flea control product, but it's a generally safe form of relief with few, if any, side effects. If you give a dog or cat with fleas a Capstar tablet, you'll literally see fleas falling off and dying approximately a half hour later.

Capstar for Pets

Nitenpyram is similar to nicotine, the active ingredient in tobacco. It kills adult fleas by acting on their central nervous systems but has no effect on eggs or larvae. Capstar enters the pet's bloodstream rapidly. As soon as a flea bites the animal after Capstar administration, it's a goner. Capstar's effect on the parasite's central nervous system causes it to drop off the animal and die. Capstar is safe enough to give to a pet every day or so, if necessary. It's available over the counter, but always check with your vet before giving your pet any medication.

Capstar and Scratching

Don't be alarmed if your pet starts scratching like crazy after you administer Capstar. That's not an adverse reaction but a normal reaction to the fleas as they leave the skin and come to the surface, prior to falling off. This is called the "tickle effect." In cats, it can last up to 6 hours, on and off, and in dogs about 4 hours. If one pet has fleas, make sure every dog or cat in the household receives some sort of flea preventive.

Side Effects

In a 2011 letter to veterinary professionals, Novartis Animal Health, Capstar's manufacturer, wrote that it was making some changes to its package insert for Capstar. Common side effects in cats include meowing and grooming excessively during the Capstar flea free-fall. Others might pant or briefly become hyperactive. The new package insert reports that, rarely, some cats experience vomiting and diarrhea, appetite loss, drooling, trembling, increased heart rate and seizures. Rare canine side effects include lethargy, vomiting and diarrhea, panting and seizures. Some dogs also experienced allergic reactions, including hypersalivation, hives, agitation and vocalization.

Capstar Contraindications

Unlike many other medications, Capstar isn't contraindicated for use with other drugs. However, pregnant or lactating dogs or cats shouldn't receive the drug, as it might cause birth defects or abortion. Kittens or puppies under 2 pounds in weight or less than 4 weeks of age shouldn't receive Capstar. If your pet shows any sign of an allergic reaction, such as hives, call your vet.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.