warning about capstar


<font color=teal>The TF waves to buzz2400's DS
Feb 14, 2001
All web pages I went to said that capstar is safe for cats to get rid of fleas. So I went and bought a pill for each of my six cats. Within 15 minutes giving the pill, two cats ran around screaming bloody murder. So I took them into the bathroom and just kept using the flea comb. I then go to check the other cats and one cat is panting real bad. It was very hot and humid so I brought him into an air conditioning room. I then started to read the pamphlet of capstar but lo and behold, no info on adverse effects, in fact really no info. So I call the pet store where I bought it and she said she never heard anything like that and not to worry. While I'm on the phone, this cat disappears. So I start looking for the other cats and I find another cat panting real bad. I bring her in the air conditioned room and she is running back and forth panting. So I try looking online for capstar for adverse effects and finally find something that states some cats do start panting, vocalizing, vomiting, etc. So I call the 24 hour vet and they said if she is still panting in 20 minutes to bring her in. So after 20 minutes, still panting and running around like crazy, I bring her to the vet. I still never found the other cat who was panting. So anyway, I get minnie to the vet and they immediately take her to give her oxygen. After about 1/2 hour vet says minnie stopped panting. They took her temp and she was normal. So he told me to call poison hotline which I did but they wanted $65 and then told me they could not help me because I did not know the dose. In the meantime, my son calls me and tells me he found the missing cat who was panting and he seemed fine so I told vet I just wanted to take minnie home to monitor her. So after $200, waiting around for 2 hours at the vet, everything seems fine now.

I'm really just wanting to warn people who are thinking of using capstar. There are sometimes adverse affects. If you are thinking of using it, use it when you can monitor the cat, do it during the hours when you vet is around (today is sunday so I had to pay alot), and don't do it when it is hot and humid. I used it on six cats and four had adverse effects, and it was the correct dose because I weighed each cat this week. I know I rambled but I just don't want someone else to go through what I did.


DIS Veteran
Apr 14, 2011
Wow, that's scary. :grouphug: Glad they are feeling ok now. What a ride!

Adding, NEVER use the stuff Hartz has for cats or dogs, this stuff has killed multiple animals and they still put it out there, it's not worth the risk to use the cheap stuff.

(I have no idea if Capstar is cheap, I'm talking about Hartz, I won't even buy their toys anymore)


DIS Veteran
Jun 26, 2007
Thank You for warning us !
I'm happy all of your kitties are okay now,
I googled it and CapStar`s main ingriedent is related to nicotine, which would explain the reactrion, this is a stimulate they have never been in contact with. Here's what I found.

How Nitenpyram works:

Nitenpyram is a neonicotinoid chemical, which, loosely translated, means: "new or novel nicotine-related" chemical. Neonicotinoid insecticides are synthetic variations of nicotine: a natural alkaloid compound that exists within the leaves of a variety of plant species of the Genus Nicotiana, including those trees responsible for producing tobacco (as in cigarettes). Nitenpyram and other drugs of the neonicotinoid family (e.g. imidacloprid as found in the flea control product: Advantage) act on the same bodily receptors as the drug nicotine does. These receptors are called nicotinic acetylcholine receptors (nAChR).

Nicotinic acetylcholine receptors in animals:
Nicotinic acetylcholine receptors (nAChR) are found in many locations within the animal nervous system. They are present in the synapses of the nerve bundles (called ganglions) supplying the parasympathetic and sympathetic nervous systems and they are also present on the surface of the animal's muscle cells where the nerves supplying the muscles make close contact (another form of synapse connection whereby the nerve end plate sends a chemical signal (a chemical called acetylcholine or ACh) to the muscle cells over a synaptic gap).


Many of the adverse effects reported in dogs and cats following the administration of Capstar flea medication are excitatory effects including: hyperactivity, panting, nervousness, fever, vocalisation and an increased heart rate. In extreme cases, these excitatory effects have tipped over into marked gastrointestinal effects (vomiting, decreased appetite, diarrhea, salivation) and moderate to severe neurological signs (difficulty breathing, incoordination, seizures, trembling, pupil dilation), some of which have the potential to result in death (e.g. seizures). Allergic reactions have also been described, manifesting as: hypersalivation, fever, hives, swollen or puffy eyes, itching and redness. In seeming contrast, some animals have shown signs of depression and lethargy, rather than excitation, when given Capstar flea medication

Again OP Thank You for the warning !
  • buzz2400

    <font color=teal>The TF waves to buzz2400's DS
    Feb 14, 2001
    castmember thanks for posting that. The same pet store that sold me the capstar told me I should switch from frontline to advantage because of my flea problem. What you posted stated that advantage has same kind of chemicals. I think I will stay with the frontline. I am still checking on all of the cats and probably will all night long.


    Earning My Ears
    Oct 1, 2014
    okay on using capstar on your cat. the vet found one flea on my cat and she gave her capstar and then put advantage II on her as well . I took her to the vet for acne on her chin that day. Well needless to say after I asked her if that was to much poison on her she said no she will be okay, well found out she stopped eating and became lethargic . Then she gives her antirobe for her acne she said no side effects well that was again incorrect antirobe makes them have gastrointestional problem and she stopped eating and began hiding from me so I took her to a different vet and he told me that she now has blood in her urine as antirobe can cause kidney problems Im like for real Im so mad so I sugggest to anyone out there even if you trust your vet ( which I have had mine for 15 years) BEFORE you give your beloved family member anything they prescribe do a search for the side effects online and then use your judgement or talk to your vet about it mine said all those meds would not upset her stomach and behold they did and now Im dealing with a very skinny cat that has kidney problems now buyer beware about all these products and my cat is an inside cat and she probably picked up the flea at the vets while waiting as she had no flea dirt on her and I have never seen another one yet on her or in the house on stuff


    Chris Isaak fan
    Jul 13, 2000
    I'm sorry to hear that your cat had such a rough time with Capstar. My indoor-only cat has had fleas for a year now. I was putting Frontline on him, but it really wasn't working. The Vet gave him a dose of Capstar and the next day, I started him on Advantage II. He was a little lethargic, but I'd rather have that and the fleas gone. I vacuumed like crazy, washed linen and sprayed the areas he had been hanging out around.

    I can see that it would be too much for some cats.


    DIS Veteran
    Aug 20, 2012
    poor kitty, :sick:

    Thanks for the info.

    Hope they are all doing fine, let us know.
  • lovesmurfs

    DIS Veteran
    Jun 24, 2006
    It's a two year old thread, bumped by a spammer, so don't be dissapointed if OP doesn't update.;)
    Definitely a zombie thread, but it might not be a spammer, perhaps someone who had done a search for capstar side effects or something and had the thread come up -- signed up on Disboards to comment. I've done that on other sites inadvertently.


    Earning My Ears
    Apr 21, 2015
    I have a sensitive little kitty named Kiki. She got tapeworm from eating grass outside my apartment. So I took her to the vet and they gave her Profender. It was $35 for the med alone. I took her home and she got so sick, she almost died. Two weeks later I noticed she still had tapeworm!!! So I checked online for a more natural way to go and I found Praziquantel at Little City Dogs. (I hope it's okay to say their name, I'm not trying to advertise, just save some kitties lives). I personally gave her 1-1/2 capsules (I emptied half out of one of them). It worked so well and she didn't even notice anything! (It dissolves the worms inside). Anyway, about the other med she uses; Revolution (applied on the back of the neck) it takes care of fleas, heartworm, ear mites, hookworm, roundworm, and whipworm. I was thinking about ordering Nitenpyram, because it's almost $20 for Revolution and you have to get it at the vets, but everything I've read about Nitenpyram (yikes!) makes me happy to stay with what I'm already using. Kiki is allergic and sensitive to smoke, pollens, dust, meds, etc. So I thought maybe this would help someone searching for the mildest meds for your pets.:lovestruc PS: I don't use Revolution on her every month like they want you to, she does fine with it every 3 months. But you can find out what works best for your cat.
    Last edited:

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