Capstar Flea Treatment: Review and Side Effects

What is Capstar?

Capstar is a flea treatment for cats and dogs produced by Novartis Animal Health.  It comes in tablet form and starts to kill fleas within 30 minutes.  Sounds absolutely great, right?  Yes, it is, and in my opinion products like Capstar have their place in flea control.  But, you need to know that Capstar isn’t a total solution to getting rid of fleas.

Capstar flea treatment tablets are fast acting, but are they totally effective?

This post is about:

  • How Capstar works
  • Problems with using Capstar as a flea treatment
  • Possible side effects associated with Capstar
  • How to use Capstar effectively to help get rid of fleas 

How Capstar kills fleas

Capstar contains the insecticide Nitenpyram.  Nitenpyram is used both agriculturally and by veterinarians to control external parasites, including fleas.  Capstar is administered as a tablet and takes only 30 minutes to start killing adult fleas.  Within 4 to 6 hours it should have killed all the adult fleas on your pet.

The fleas are killed almost instantly as the nitenpyram interferes with their nervous system.  Novartis, the manufacturers of Capstar, claim that you can see dead fleas falling from your pet.

Capstar has no long term effect; within 24-48 hours it is out of your pet’s system.

Why Capstar is not a total solution to flea control

There is no questions that Capstar is totally effective at killing the adult fleas on your pet.  The problem is that only a tiny fraction of the flea population are adult fleas living on your pet.  The vast majority of fleas are living around your home in various immature stages of the flea life cycle.  Whilst Capstar will kill today’s adult fleas on your pet, they will rapidly be replaced by more tomorrow.

(Read more about the life cycle of a flea – it’s essential information for getting rid of fleas!)

An effective flea control regime needs to target all stages of the flea life cycle not only on your pet, but around your home.  Spot-on treatments, like Frontline and Advantage, provide an ongoing protection for your pet, for up to a month.  In addition, sprays or powders, (chemical or natural), combined with regular vacuum cleaning, will take care of the fleas around your home.

(Read more about getting rid of fleas in your home).

Possible Side Effects of Capstar

Nitenpyram, Capstar’s active ingredient, is a very safe insecticide.  The product is marketed as being safe for even young kittens and puppies (over 4 weeks and weighing more than 2 pounds) and pregnant and nursing animals.

Despite being safe, it has been reported that rarely some cats become agitated (including excessive grooming, meowing) and may pant after a couple of hours of Capstar being administered.  However, no long term problems have been noted.

Using Capstar as Part of a Flea Control Regime

Despite the fact that Capstar should not be used as a total solution for flea control, it can have a place in managing fleas when used as a complementary treatment, due to its rapid effect on adult fleas.  Here are some circumstances in which it is an effective addition to your flea control regime:

  • Animals with flea allergy dermatitis need rapid relief from the bites of adult fleas.  Spot on treatments can take several days to be fully effective.  Use Capstar to give almost instant relief.
  • If there is a severe infestation you may like to use Capstar to quickly remove the adult fleas on your pet before applying a spot on treatment and spraying your home.
  • After using a spot on treatment and spraying your home you may find a few “stragglers” who managed to escape – use Capstar to kill them off.

Capstar is safe to use with other other flea treatment products and medicines 


  • Capstar is a proven and safe treatment for adult fleas
  • Capstar should not be used as your sole means of flea control
  • Capstar can be used with other products to provide instant relief from fleas
  • Other flea control treatments need to be used for long term protection from fleas








3 thoughts on “Capstar Flea Treatment: Review and Side Effects

  1. Well, It’s 8:45 a.m. and i just gave a rat terrier, cat, and boxer capstar. I’ve spray the home and anything with cloth on it. I put the dogs outside and the cat in the attached garage on a white sheet. I’ll give it 45 minutes on the cat and i’ll see what happpens

    • Hi Dawn – the Capstar will sort out the adult fleas on the animals. Hopefully the spray will kill some of the eggs/larvae in the house. A tip – they aren’t just on fabric – they’ll live in gaps in the skirting board, where ever there’s a dark space. Hoover – hoover every day for a month or so!

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