For a cat weighing 2 to 25 lb and at least 4 weeks old, the U.S. consumer label for Capstar (nitenpyram) directs one 11.4 mg tablet to kill adult fleas on the cat. If fleas reappear, the label allows another dose as often as once per day. Capstar works only on adult fleas living on the animal. It does not reach flea eggs, larvae, or pupae in the home, so the environment can keep supplying new fleas after the tablet has done its job.
The guidance below follows the current U.S. label (updated August 19, 2026) and FDA announcements dated through September 2026. Dosing and product availability can differ by country and change over time, so treat this as a summary of the labeled directions, not individualized veterinary advice.
What Capstar is and who the label covers
Capstar is an oral tablet containing nitenpyram, a neonicotinoid that kills adult fleas. In the United States it is an over-the-counter animal drug label approved under NADA 141-175. The labeled flea-treatment indication covers dogs, puppies, cats, and kittens that meet two minimum requirements:
- Body weight of at least 2 pounds
- Age of at least 4 weeks
The label instructs owners not to give the product to any pet under 2 lb. Because the label’s safety caution is strongest for the youngest and smallest animals, eligibility for kittens is discussed in its own section below.
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- CAPSTAR for cats (nitenpyram) starts killing adult fleas in just 30 minutes
- With one dose of CAPSTAR cat flea medication, you can watch the dead fleas fall off your pet
- If your pet gets reinfested with fleas, simply give another dose of the cat flea pills as often as once a day
- CAPSTAR nitenpyram for cats is a fast, effective flea treatment that is available over the counter
- CAPSTAR oral cat flea treatment (11.4 mg) is safe for cats and kittens 4 weeks and older that weigh 2-25 pounds
Capstar dosage for cats
The label tells owners to weigh the cat before every dose. The FDA’s September 2026 emergency-use summary repeats the same instruction in plain terms: “Weigh your pet prior to administration to ensure proper dosage.” Use the table below to match your cat’s weight to the correct tablet.
| Animal and weight | Tablet on the U.S. label | Status for cats |
|---|---|---|
| Cat under 2 lb | None | Do not administer (label minimum weight) |
| Cat 2 to 25 lb | One 11.4 mg tablet | This is the labeled cat dose |
| Dog 25.1 to 125 lb | 57 mg tablet | Dog dose only; not listed as the cat dose |
The 57 mg tablet is a common source of confusion. Never use it for a cat, regardless of how large the cat is.
How to give Capstar to a cat
- Weigh your cat and confirm it falls within 2 to 25 lb. Select the 11.4 mg tablet.
- Give the tablet orally. You can place it directly in the mouth or hide it in a small amount of food.
- If you hide the tablet in food, watch the cat until it has eaten the food and appears to have swallowed the tablet.
- If you are not sure the cat swallowed the tablet, the label says it is safe to give a second tablet.
- Treat every pet in the household that has fleas. Untreated pets can keep fleas in circulation.
Repeat dosing for reinfestation
The label says one dose should kill the adult fleas on the cat. If the cat is reinfested, another dose may be given as often as once per day. This once-daily flea instruction is specific to the routine flea indication. It is not the same as the screwworm emergency-use schedule described later in this article.
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- CAPSTAR for cats (nitenpyram) starts killing adult fleas in just 30 minutes
- With one dose of CAPSTAR cat flea medication, you can watch the dead fleas fall off your pet
- If your pet gets reinfested with fleas, simply give another dose of the cat flea pills as often as once a day
- CAPSTAR nitenpyram for cats is a fast, effective flea treatment that is available over the counter
- CAPSTAR oral cat flea treatment (11.4 mg) is safe for cats and kittens 4 weeks and older that weigh 2-25 pounds
Kittens, small cats, and pregnant or nursing cats
Kittens qualify for the flea indication only if they are at least 4 weeks old and at least 2 pounds. Kittens near that threshold are the group in which caution matters most. The label reports that the frequency of serious signs, including neurologic signs and death, was higher in animals under 2 lb, under 8 weeks old, and/or reported to be in poor body condition. Those are post-approval reports and do not establish that the product caused each event, but they are the situations in which a veterinarian should be consulted before treatment.
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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsPregnant and nursing cats need the same level of care. The label reports birth defects and fetal or neonatal loss after treatment of pregnant and/or lactating animals. The label’s other-information section also states that Capstar is safe for pregnant or nursing dogs and cats. Both statements appear on the label, and both should be considered together. A veterinarian should make the decision for any pregnant or nursing cat.
Capstar side effects in cats
Reported adverse events
The label lists the following post-approval adverse events in cats, in decreasing order of reporting frequency:
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- FAST-ACTING: One oral cat flea pill starts killing fleas within 30 minutes of administration
- SAFE TO USE: This cat oral flea treatment is safe for kittens and cats from 2-25 lbs; 4 weeks and older, when used as directed
- TREAT RE-INFESTATIONS FAST: If your pet gets reinfested with fleas simply apply another dose as often as once a day; CAPACTION Cat Flea Pills are even safe for use on pregnant or breeding cats
- EASY TO USE KITTEN FLEA TREATMENT: Without the mess and rubbing off of a flea and tick topical treatment and without the need of a veterinarian prescription, this oral cat flea treatment is administered orally to kill adult fleas fast
- KILL FLEAS EFFICIENTLY: Includes 6 doses of CAPACTION for cats, killing adult fleas that may cause allergy dermatitis
- Hyperactivity
- Panting
- Lethargy
- Itching
- Vocalization
- Vomiting
- Fever
- Decreased appetite
- Nervousness
- Diarrhea
- Difficulty breathing
- Salivation
- Incoordination
- Seizures
- Pupil dilation
- Increased heart rate
- Trembling
The order describes how often events were reported to FDA, not how often they occur in cats. The label states that not all reactions are reported, that the data cannot reliably estimate how frequently an event happens, and that causation cannot be established from these reports. No incidence percentage is published for these events.
Scratching and temporary restlessness
The label says a cat may scratch as fleas begin to die. It describes this as temporary and says it may look like brief hyperactivity, panting, vocalization, or excessive grooming and licking. That explanation applies only to mild, short-lived changes. It should not be used to excuse severe or persistent signs, which need veterinary attention.
Serious signs that need a veterinarian
Seizures, trouble breathing, marked incoordination, severe lethargy, and any neurologic sign warrant an immediate call to a veterinarian. The label itself advises consulting a veterinarian about medical problems associated with flea infestation or about flea-control questions.
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- Fresh scented
- Kills and repels fleas and ticks, plus prevents flea eggs from hatching for 7 months. Can be worn simultaneously with your cat's regular collar
- Water-resistant design won't cause loss of effectiveness if your favorite feline takes a stroll in the rain
- Features a breakaway, safety release snap
- For use on adult cats and kittens 12 weeks of age and older
What Capstar controls and what it does not
The label states that the tablet begins working within 30 minutes. In label studies, Capstar was reported to be more than 90% effective against adult fleas within 6 hours in cats, and within 4 hours in dogs. These figures come from the label’s study results. They are not a guarantee for every cat, and they say nothing about flea eggs or immature stages.
Capstar does not affect fleas in the pet’s environment. Immature fleas in bedding, carpet, and other protected areas can develop into adults and reinfest the cat. For that reason, the label says treatment may be needed more than once, and it recommends treating all infested pets. Environmental control, such as cleaning bedding and vacuuming, is a separate task that the tablet does not perform.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Regulatory updates in 2026
FDA-approved generic nitenpyram
On June 10, 2026, FDA announced approval of generic Nitenpyram Tablets for flea treatment in eligible dogs and cats. FDA said the generic has the same active ingredient as Capstar and is bioequivalent to it. The announcement described 11.4 mg and 57 mg tablet sizes and over-the-counter availability. The announcement does not confirm which retailers stock the generic, so check the label of any specific product before use. You can read the announcement at FDA’s notice on the generic nitenpyram approval.
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Emergency use for New World screwworm
On September 3, 2026, FDA announced an emergency use authorization (EUA) for Capstar to prevent and treat New World screwworm (myiasis) in eligible dogs and cats. FDA describes most U.S. pets as currently at low risk, because confirmed cases are limited to a specific geographic region. Owners of animals that live in, travel to, or return from affected areas should monitor them closely. FDA says visible maggots or foul odors in wounds or body openings require immediate veterinary care. The emergency use is separate from the flea indication, and it remains in effect only while the underlying emergency declaration is in force, unless FDA revokes it earlier.
The table below separates the routine flea label from the EUA. The two uses have different schedules and different legal status.
| Feature | Routine flea treatment | New World screwworm EUA |
|---|---|---|
| Legal status | FDA-approved (NADA 141-175) | Emergency use authorization, September 3, 2026; temporary |
| Target | Adult fleas on the pet | Prevention and treatment of New World screwworm in eligible dogs and cats |
| Cat dose | One 11.4 mg tablet for 2 to 25 lb | 11.4 mg for dogs or cats 2 to 25 lb |
| Schedule | One dose; may repeat as often as once daily if reinfested | Treatment: second dose 6 hours after the first. Prevention: once daily |
| Primary source | DailyMed consumer label, updated August 19, 2026 | FDA Freedom of Information Summary, Capstar EUA 006688, September 2026 |
Do not apply the screwworm schedule to routine flea control, and do not apply the flea schedule to screwworm. The FDA summary states that the approved indication remains adult-flea treatment and that the screwworm use is an emergency authorized use. FDA’s press announcement on the EUA, which includes a statement from Timothy Schell, Ph.D., director of the agency’s Center for Veterinary Medicine, is available at FDA’s announcement on emergency use for New World screwworm.
When to call a veterinarian before giving Capstar
The label is written for general use. A veterinarian should review the situation before treatment, or as soon as possible afterward, in these cases:
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Quick Recap
- The cat is under 2 lb, under 8 weeks old, or in poor body condition
- The cat is pregnant or nursing
- The cat is already taking other medicines or other flea products. The label says Capstar may be used with other products, but that statement does not replace a review of the cat’s specific medications
- The cat has a medical problem linked to flea infestation, such as skin disease or anemia
- Any serious sign listed above appears, or symptoms persist beyond the mild, temporary changes the label describes
- Visible maggots or a foul odor appear in a wound or body opening, which requires immediate veterinary care
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