Capstar for cats: the 30-minute flea tablet explained

What is Capstar for cats?

Capstar is an oral flea treatment made by Elanco. Each tablet contains nitenpyram, an insecticide that is absorbed into the bloodstream within minutes. When fleas bite, they take in nitenpyram, which overloads their nervous system and kills them quickly.

The same speed that makes Capstar so useful also limits it: nitenpyram is cleared from your cat's body within about a day. So Capstar is a "rescue" treatment, not a preventive. Our guide to flea treatment for cats explains how to choose a long-acting product to use alongside it.

How fast does Capstar work?

Time after giving Capstar	What happens
15–30 minutes	Fleas start dying
Up to 6 hours	Most adult fleas on the cat are dead
About 24 hours	Nitenpyram has left the body; no further protection

As fleas die they often move to the surface of the coat, so you may see your cat scratching, twitching its skin or grooming more for an hour or two. Dead fleas may fall out onto bedding. This is a sign the tablet is working, not an allergic reaction.

Who can use Capstar for cats?

Capstar for cats and small dogs

The same Capstar 11.4 mg tablet is licensed for cats and for small dogs weighing 1 to 11 kg, so households with a cat and a small dog can use one pack for both. Larger dogs need the higher-strength dog tablet. This is one of the few flea products that is safe to share between species at the same dose, but never give a cat any other dog product.

Capstar for cats with other health conditions

Because nitenpyram leaves the body so quickly, Capstar is often a good option for elderly cats or cats on other medicines, when a vet wants to avoid long-acting drugs. Tell your vet about your cat's health and medicines before using it, especially if your cat has kidney disease or has had seizures.

Capstar dose for cats

Product	Weight	Dose
Capstar 11.4 mg tablets for cats and small dogs	1 kg to 11 kg	1 tablet

One tablet strength covers almost all cats. Capstar can be given once a day if new fleas keep appearing, but check the leaflet for the latest dosing advice. It can be given with or without food; many owners find it easiest to hide in a small treat.

When should you use Capstar?

• A heavy infestation, to give fast relief while a monthly product starts working.
• A new kitten, rescue or stray cat arriving in your home with fleas. Our guide on how to tell if a cat is a stray or feral explains what to check first.
• Before a cattery stay, a vet visit, or travel, so your cat doesn't bring fleas with it.
• Cats with flea allergy that are suffering during a flare-up.
• Young kittens from 4 weeks and 1 kg, which can't yet use many other products.

How to give Capstar to your cat

1. Hide the tablet in a small piece of soft treat, cooked chicken or wet food, and offer it on its own so you know it's eaten.
2. Or give it directly: tilt the head back gently, open the mouth and place the tablet at the back of the tongue, then close the mouth and stroke the throat.
3. Watch for 30 minutes. You'll often see fleas surfacing on the coat.
4. Comb your cat over a white towel to remove dying fleas.
5. Start or continue a long-acting flea product and treat your home.

Our step-by-step guide on how to give a cat a pill has extra tips for cats that refuse tablets.

Capstar vs monthly flea treatments

	Capstar	Monthly spot-on or tablet
Speed	15–30 minutes	8–48 hours
Protection	About 24 hours	4 weeks (some 12 weeks)
Kills eggs or larvae	No	Some do
Ticks or worms	No	Some do
Prescription	No	Depends on product
Best use	Rapid knock-down	Ongoing prevention

For long-lasting oral protection, see our guide to flea tablets for cats. Popular spot-ons include Frontline and Advantage.

Clearing an infestation with Capstar: a 3-month plan

Capstar alone won't clear an infestation because 95% of fleas live in your home as eggs, larvae and pupae. Use this plan:

1. Day 1: give Capstar to every infested cat (dogs need their own product), apply a monthly flea treatment, and wash all bedding at 60°C.
2. Days 1–21: vacuum every day, including under furniture and in the car, and treat the home with a household spray containing an insect growth regulator. Give Capstar again on days when you see live fleas, if needed.
3. Months 1–3: keep every pet on monthly flea treatment without gaps. Flea pupae can hatch for weeks.

Cats with fleas usually need a tapeworm treatment too. See our cat worming guide.

Capstar side effects

Capstar is well tolerated. Possible side effects include:

• Temporary increased scratching, licking or restlessness as fleas die.
• Rarely, vomiting, drooling, hyperactivity or panting.

These usually pass within a few hours. If your cat seems unwell, has repeated vomiting or shows trembling or seizures, contact your vet straight away.

Capstar for kittens, pregnant and nursing cats

Capstar is licensed for kittens from 4 weeks of age that weigh at least 1 kg, making it one of the earliest options for flea-ridden kittens. It is also considered suitable for pregnant and nursing cats, but always check the current leaflet and ask your vet first. Treating the mother cat and her bedding is important, as kittens pick up fleas from her and from the nest.

How much does Capstar cost?

Capstar for cats is usually sold in packs of 3 or 6 tablets and costs around £2 to £4 per tablet from vets, pharmacies and pet retailers. Because it only lasts a day, it's a short-term cost: most owners use it for a few days at the start of a flea problem, then rely on a monthly treatment.

Why am I still seeing fleas after Capstar?

If you see fleas again a day or two after Capstar, the tablet hasn't failed. It has simply left your cat's system, and new fleas that hatched in your home have jumped on. The answer is to:

• Start a long-acting flea treatment on every pet.
• Vacuum daily and treat the home.
• Keep going for at least three months.

If you have dogs too, remember they need a dog-licensed product. Our guide to whether dogs can get cat fleas explains how fleas move between pets.

Capstar and cats with flea allergy

Some cats are allergic to flea saliva. A single bite can trigger days of intense itching, scabs along the back and neck, and over-grooming that leaves bald patches. For these cats, killing fleas as fast as possible makes a real difference to comfort. Capstar can bring quick relief during a flare-up, while your vet may prescribe a fast-acting long-term product and, if needed, anti-itch medicine. If over-grooming has led to hairballs or bald patches, our guides to hairball remedies and calming a stressed, over-grooming cat can help.