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Capstar for Cats

Written By Tim Falk
Published: 07/20/2021Updated: 07/21/2021
Capstar for Cats

Capstar is a fast-acting flea treatment medication suitable for use on cats and dogs. Capstar features the active ingredient nitenpyram, and it starts killing fleas 30 minutes after your cat has been treated with the medication.

Capstar is designed to offer a more convenient way to kill adult fleas than through the use of a topical treatment, and it can help protect your pet against flea allergy dermatitis.

If you’re thinking of using Capstar for cats to treat your feline for a flea infestation, keep reading to find out all about the appropriate dosage, efficacy, safety, and potential side effects of the medication.


You don’t need a prescription to purchase Capstar for cats over the counter. Available in tablet form, Capstar is sold in 11.4-milligram tablets for cats and small dogs, and in 57-milligram tablets for larger dogs. A 6-pack of 11.4-milligram tablets for cats commonly sells for around $28 to $32 from online retailers.


Capstar for cats is designed for use on cats that weigh between 2 pounds and 25 pounds. Your cat must be at least 4 weeks of age in order to be given the medication.

The minimum recommended dosage amount of nitenpyram, the active ingredient in Capstar, is 1 milligram per kilogram of body weight. You can give the tablet to your cat directly, or hide it in your pet’s food for easier consumption.

Follow the instructions on the label when administering Capstar to your cat.


According to the label, Capstar is rapidly absorbed and reaches maximum blood concentration in both cats and dogs 1 hour after being administered. The medication kills more than 98% of fleas on the animal inside 6 hours, with all adult fleas killed within 24 hours of treatment.

In one clinical trial involving 123 cats and 88 dogs, researchers examined the efficacy of nitenpyram tablets on flea infestations. Results showed that fleas started to fall off the animals in the study 30 minutes after treatment, and nitenpyram had 95.2 percent efficacy on cats 6 hours after treatment. No animals recorded adverse reactions to nitenpyram during the clinical trial.

Active ingredient

The active ingredient in Capstar for cats is nitenpyram. A neonicotinoid compound, nitenpyram inhibits normal nerve transmission in fleas to cause the death of adult fleas.

Side effects

There are no known adverse effects of the use of Capstar in cats or dogs. According to the label, the medication has been administered to cats and dogs in conjunction with a range of other common veterinary products, including antibiotics and corticosteroids, without causing any adverse effects.

It’s worth noting that the use of nitenpyram may result in some itchiness and scratching for your pet; however, rather than a reaction to the drug, this is a temporary reaction to the dying fleas.


Capstar for cats should never be given to kittens less than 4 weeks of age. However, it is safe to give to pregnant and lactating females, as well as to cats used for breeding. 

Drug interactions 

There are no known drug interactions to report. It’s also worth mentioning that feeding does not affect the absorption of Capstar, so tablets can be given with food if needed.

Allergic reactions and sensitivity

This medication should not be given to cats that are allergic to it. Symptoms of an allergic reaction could include hives, swelling, and difficulty breathing, so seek veterinary attention if you notice any of these symptoms.

Frequently asked questions

Does Capstar kill immature fleas?

No, Capstar is a flea adulticide that kills adult fleas. It doesn’t kill flea eggs or provide ongoing protection for your pet against fleas. To completely eliminate a flea infestation, it may need to be used in conjunction with a product that kills fleas at the immature stages of their life cycle.

How should I store Capstar for cats?

Capstar should be protected from humidity and stored at temperatures below 25°C (77°F). It should also be kept out of reach of children at all times.

How often can Capstar be used? 

If needed, Capstar can be used daily to control a flea infestation.

Can I use Capstar in conjunction with a flea shampoo?

Yes, it’s safe to use Capstar alongside a flea shampoo if necessary. 

What should I do if my cat has an adverse reaction to Capstar?

If your cat has a negative reaction to this or any other medication, contact your veterinarian immediately. 

How long do Capstar tablets last before they expire?

Capstar tablets have a shelf life of 3 years from the date of manufacture. 

Where can I find out more information about Capstar for dogs?

Check out our Capstar for dogs guide for more details.

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