Comfortis For Cats?

    If you want to read other user claims, scroll below this article.

    Comfortis for cats
    Comfortis for cats

    If you have a cat , and your cat has fleas, then maybe you have asked and Googled to see if they have Comfortis For Cats.
    I know I have. Rest assured, they do.
    The pills are huge. Close to the size of a nickle. but thick like heart burn medicine.

    Comfortis does not say it will kill ticks. I asked the vet why, and she said “Anything digested that can kill ticks, will kill cats”.

    Currently the pills still say “for dogs” on them. and the dog’s weight is a bit greater than what a cat’s weight would be. See I have a 22 LBS giant domestic cat (Oreo), and the pills say “For dogs between 20.1-40 lbs”. While the chart for weight conversion the vet had on her wall showed cats weighing between 12 -21 lbs
    Today is day 1 and I am just now giving Comfortis to my cat. I crushed the pill and powdered the Comfortis and mixed in with the canned food, but only about 1/4 of a can. I know that my cat will always conserve about 1/3 of available food for later so the mix ratio is a bit high. As my cat  stops eating to save some for later, I walk back into the feeding area, grab his food bowl and scoop the remaining food to the side, I add more of the fresh juicy food then put his old licked up food on top, and then pour more juice on the top. He is eating fine, and the Comfortis is being ingested.

    Warnings I was given are:

    • wait 1 month after any flea spray or drops or flea chemicals used, before giving Comfortis to your cat
    • Make sure your cat does not consume Comfortis on an empty stomach

    I do not recall any other warnings. I did however have to take Oreo to the vet and have him inspected and weighed and given a light check up, before the vet would give us the pill.
    My pill was $17ish before tax. $19+ after tax.

    Will report back when I get results.

    Comfortis Pill
    Comfortis Pill for dogs can be used for cats

    Here is the Comfortis Website
    Here are the warnings and symptoms for Comfortis

    **Update 1**

    Almost an hour and a half later I am seeing the fleas on top of his fur. Dead. Comfortis seems to be working very well.
    My cat feels a bit warm to the touch, but he has not vomited yet, nor has he shown any symptoms of diarrhea.
    Well I like this stuff. If this works for as long as they advertise, then Comfortis will be a permanent fixture in my house.
    **End Update 1**

    **Update 2**

    The Comfortis made it for an entire month. (along with vacuuming religiously) Not a flea in the house.
    My cat’s fur has grown back and he is no longer scratching, and the fleas are no longer jumping on me when my cat sits in my lap.
    I still run the comb through his fur. Not as often as before but still do it because he is spoiled now.
    No fleas on the comb.
    No detectable side effects. Playing well and finally leaving the kitchen and walking on the carpet again.
    **end update 2**


    Please read all warning labels, I may have missed some warnings and new warnings may have come up since I gave my cat Comfortis. Though my cat had no side effects from Comfortis, your cat might.

    From all of the Google searches I have seen people who have animals with liver issues should avoid Comfortis until permitted by the vet.
    Also if your pet is on any worming medicine, or taking any other flea medication, see the vet and be ready to give specific dates of dosage.

    What to do if you give to much Comfortis to a cat: Call an emergency vet clinic quick.
    What to do if your cat eats your dog’s Comfortis: call an emergency vet clinic quick.


    1. linda haven | |

      I too usedx the product from my Vet, and it nearly killed my 13 yr. old cat. 3 cats, only 1 would eat his food w/the drug and he nearly died! Vomiting, lethargic for days and refused to eat for more than a week. Another trip to the vet for re-hydrating & blood work to see if his kidneys/liver were still working. after 2 weeks and trying everything I could think of to get him to eat, he’s slowly starting to show interest in food again. Def would NOT recommend this product to anyone! Too many other products on the market to take a chance on this TOXIC product.

    2. TruXter | |

      Sounds a bit fishy.
      You say ” 3 cats, only 1 would eat his food w/the drug”
      The pills are weight specific. Each cat has to be checked out independently for the meds.
      Meaning you have to get each cat checked by the vet and a specific dose is to be given to specific cats.
      but you put the food out in the open for three cats to consume.
      It sounds like you overdosed your cat.

    3. Susan Kane | |

      PLEASE do not give Comfortis to your cats. It’s available by “prescription only” for a reason. On Dec. 31st. I had to put my beloved Bootsy to sleep after her 3rd and fatal dose of Comfortis. She was barely 7 pounds, and the vet. gave her 270mg. for 3 months. She was perfectly healthy until I started her on Comfortis on Sept. 26th. During the horrific ordeal after the 3rd dose, her bloodwork was completely “normal.” Her little tongue was developing dark red spots that would turn gray, and then that part of her tongue would fall off. This happened over the course of 3 weeks, accompanied by lethargy, drooling, and twitches in her sleep. They tried every antibiotic, and nothing would work. Everyone doubted me when I suggested that it was the Comfortis. After many hours of research, I am completely convinced that I’m correct. I found the FDA document that cleared it for cats in August… The “study” raised many flags. I’m taking the time to do this so that my cat’s death isn’t completely meaningless. I’m hoping that you don’t learn the extremely hard way like I did. From my understanding of the document, these are my recommendations if you insist on using this product:
      1. Vets. need to ask clients before each monthly dosing if the animal has experienced any of the side effects that they’ve been briefed on. If so, treatment should be stopped forever.
      2. Comfortis should not be prescribed outside of flea season and only when there is extreme infestation.
      3. Dosages should NEVER exceed 22.5 mg/lb. for cats or 13.5 mg./lb. for dogs. This should be the absolute maximum. According to the study, 100% of fleas were eradicated at much lower dosages (75 – 100mg) than those listed in the dosage chart. My vet. prescribed 270mg, and according to their chart, she just made it to the larger dosage.
      4. Vets. need to be trained/educated in matters related to drug safety and in prescribing much lower dosages. They need to follow proper diagnosis/protocol when dealing with short-term and long-term adverse reactions.
      5. Never use a drug on your pets that hasn’t been on the market for at least a year.

    4. TruXter | |

      There is a chart showing which dosage to give to cats.

      I do not understand why you did not look at the chart?

    5. Susan Kane | |

      According to the chart, cats that weigh 6.1 – 12 lbs. get 270 mg. My point is that 270 mg. was too much for my 6.8 lb. cat to ingest monthly for 3 months. I believe that vets. should use their 22.5/lb. dosage. In hindsight, if I had found this report and seen the stories on the Internet, I would have never allowed the vet. to administer the 270lb. dose. I would have discovered that the risks outweigh the benefits and would have chosen not to use it. I do have that guilt of not researching the drug before using it on my pet. I learned several lessons the hard way on Dec. 31st.

    6. TruXter | |

      You should have said something.

      The Fault isn’t on Comfortis.
      The fault of the death of a cat is on the people who let it slip by that the cat was being diagnosed with too much.

      If you notice. The pill I gave my cat is in excess of 500mg. and he survived. but he is a large large cat.
      Comfortis did not kill your cat. Humans who brought it to your cat without double checking everything, killed your cat.
      The fault begins with possibly your vet.
      I was given the option to take a dose for a smaller cat. I shrugged and said I’d go for it as is.
      and I was not required to come back in for a second helping.
      One pill did the trick for my cat.
      He is an indoor cat and has been flea free since I wrote this article.

      Did you notice any lethargy? Did you notice any lack of eating through three months use of the drug ?

    7. Jenny | |

      Anyone have any advice on what to do if your cat refuses to eat the comfortis? I tried crushing it into a powder and combining with 1 Tbsp. of soft food…but neither cat would eat it.

    8. TruXter | |

      I used a whole can of catfood. It took a while but he ate it all eventually.

    9. dave | |

      “The Fault isn’t on Comfortis.” Really? They’re the ones “training” the vets. How much are they paying you?

    10. TruXter | |

      I’m not getting paid for this.
      I tried something and it worked or my cat. The end.

    11. Helen McGann | |

      To get the cat to take the pill open it’s mouth and put the tablet at the back of tongue then hold mouth shut while stroking under the chin. Then feed the cat his food. I am going to try it on my cat because it is the best thing that has happened for controlling fleas in dogs.

    12. TruXter | |

      I wouldn’t .
      That is not how they suggest to dose the cat.
      That thing is bigger than a nickle. It’s bigger than a tums.
      You can’t swallow a tums, how can you expect your cat to do that?

      Not sure if you can call that a pill. It’s huge.

    13. gordon | |

      I’ve been using a dosage much smaller than that recommended and it is still killing fleas for one month. I have six cats. Three are kittens.

    14. Jack Valvo | |

      My wife gave our cat Comfortis on Sat. the 23rd of March about 12:00 noon by Sunday evening the next day about 9:00pm I found our cat “Gizmo” dead on our bed. Dr. Brannon who reports to the FDA has made a case for this incident. We went out about 4 hours prior to his passing and he seemed fine. At this point we don’t know if it had something to do with the flea med. or it was something else.

    15. TruXter | |

      Did you follow all of the precautions? Such as no flea shampoo for (whatever suggested amount of) weeks before giving Comfortis? Did you feed your pet properly while giving the meds? Did you give the proper dosage?

      Every person I know who has given a cat Comfortis, their cats are fine.
      I would hate to lose my cat, so please update with as much detail as you can. It is getting close to flea season again.

    16. Jan | |

      Very worried about my cat. I gave him the Comfortis yesterday early evening after he ate. Now this morning, he ate but he won’t let me pet him and seems to be in pain but from what, I can’t say. It’s Saturday, so no vet. He can walk and jumped on the bed to sleep but he seems to be in pain. I can’t think what is wrong.

    17. Sartu | |

      I too have given my 13 old cat comfortis for 2 months in a row. She was healthy and full 22 lb kitty in the beginning. The 2nd dose took her down for a week, tremors and it might have exaggerated her arthritus, it was manageable and she was more active beforehand. I could barely get her to eat, and now she is only eating 1/4 the norm if and when she eats. She has lost weight and is just blah. She seems to be shedding excessively. This cat is vetted and sees the vet every few months and has her blood checked 1 or 2 times a year ( I will do everything I can to insure she is around for a long time, comfortably). I can’t seem to get her out of this funk and this is the only thing that I believe could have caused it. I will never give it to her again. HOWEVER, my other 13 old cat vomited like the exorcist after it was given to her but afterward was okay. She does not have any noticeable side effects. Bottom line , if your cat has had any health issues(1st cat) and is not a perfect picture of health (2nd cat) I would not use it especially in older cats.

    18. PJandNOodles | |

      Very glad I found this page…I have a 1 year old kitty she is only 6 lbs, I took her in to be spayed on Monday, and asked about flea control bc I am having a serious infestation in my house, and they gave me this pill, though it was a bit smaller, not the size of a tums or a nickel. Still. I gave it to the kitty the following day {Tues} as instructed. No vomiting or other visible signs of side effect except lethargy. Normally she is very perky, running around like crazy, eats a ton, tries to eat my food if I have any, likes to be in the same room as me, very vocal, but all this week she has been hiding, not eating too much, quiet and timid, I’m not sure if she’s mad at me, in pain from being spayed or it’s the flea pill but I don’t think I will use it again, just in case.

    19. laura | |

      To Jenny…anytime I have to give my cats pills, , I crush it up and mix it with hairball stuff.. its like a gel. Then I put it on my finger, open their mouth and just shove it in there lol, like on the cheek or teeth. Not always easy, but for me it works better than other ways.

    20. laura | |

      does anybody know if I can give my cats Comfortis for dogs if it’s the proper dosage? I don’t know if the ingredients are the same, tho I did do some research.
      BTW: this stuff really works great for my golden retriever. I only give it to him every other month..actually to save money, lol, but it works! thanks in advance

    21. Amy | |

      I have 7 cats, 1 with severe flea allergies. Last summer we had a massive infestation, that we could not get under control, and my vet prescribed Comfortis for all my cats. The most serious side effect any of them had, was maybe throwing up once an hour after giving it to him, and then he was fine. I noted that he hadn’t ate as much as the others after I gave him the pill. From then on I made sure they all ate enough after taking the pill. I told my vet about him throwing up, he wasn’t concerned about it.

      My cats varies in ages, 1 thru 7, range in sizes and weights, the heaviest coming in at 15lbs and the lightest at 8, and they all have there own “health conditions”, and I never had any problems with the Comfortis because of that.

      I gave them the Comfortis for almost 6 months, and that was my only side effect. We are flea free yet again, going on 4 months.

    22. JESSICA D. WEBB | |

      I’ve got a kitten. She’s about 3 months old. When I got her, she was covered in fleas. I’ve tried frontline… Bathing her for a week straight… NOTHING is working. I want to try comfortis but you guys are seriously scaring the bejesus outta me. I’m not sure who to believe on here and who to think is just a nut case. If there is ANYONE out there who really treated their cat with comfortis, please speak up. I need to know that someone had success and there was no horrific side effects. And I haven’t found a veterinarian yet that will approve giving comfortis to a cat. I’ve been to 3. If any of you know a veterinarian who WILL prescribe it, please give me some contact information for that vet and I will call them. Thanks – Jessica

    23. TruXter | |

      What state?

    24. Squish | |

      Thanks for the review TruXter, & the comments everyone. All of the experience, information, & opinions are a great help in weighing out my options concerning using this medication.

      Excellent detailing of the Veterinary information for this medication can be found here: Others researching this treatment may find this useful.

      Earlier this year, my cat reacted to Frontline Plus For Cats with allergic contact dermatitis. She is also developing a sensitivity to Advantage. And I myself am developing a severe respiratory allergy to Advantage, & we are to the point where I don’t think either one of us can handle another dose of it. Because of that reaction, I don’t know if she is a good candidate for Comfortis, or not.

      Since she has a sensitive system, if I do try her out on Comfortis, I may start her on a much smaller dosage than the weight chart suggests, & see how she & the fleas do with it over time. If I try it, I may buy the Green box for 20.1 to 40 lbs (560mg) & cut it in quarters, administering a 140mg dose to my 11.5lb 5yr old kitty. If it doesn’t work at this dose, then it doesn’t work…I can always gradually increase it next time…but it definitely sounds like this is a potent medication & erroring on the side of caution may be wise.

      One factor I found described in an ad for this medication is do not apply it any sooner than 1 month following the application of any other topical or oral flea treatment. I wonder if some people panicked from a sudden intense flea infestation (& it is easy to do, I know the feeling…) & are jumping the gun & applying Comfortis too soon, to try to corral the problem early. If so, they would get a combined additive treatment effect between the previous flea treatment & Comfortis, & this could effectively overdose the pet.

      Patience, clear thinking, & a well-researched battle strategy really pay off concerning conquering fleas…as I once found out the hard way.

      Since it really does seem to need to be mixed well with food, I may crush it & mix with vanilla ice cream (which she loves), & administer gradually by oral syringe if she finds it unappealing.

      Thanks again for the review, & best wishes to all…& their 4 legged friends.

    25. TruXter | |

      Squish, if you can make it back here to tell how this turned out, please do.

      Would love to read it.

    26. Syla's Momma | |

      All the comments I’m reading are saying the comfortis pill is the size of a nickel. This is not true if you get the 5-10lb dosage. My dog is 3.8lbs and does absolutely fine with it as well as both my cats. I have been using comfortis for 6 months and it’s worth every penny you spend in it

    27. nata | |

      i gave my two cats comforts and a hour later they threw up . but i believe its because they where not use to the comforts anyone else have this type of side effect ? . please let me know if thats normal

    28. TruXter | |

      How did you give them Comfortis? Just an open bowl they shared? or each get separate helpings?

    29. CJ Mandel | |

      My 7 year old cat died within 6 hours of taking Comfortis. he was healthy, had annual check ups and I even had an autopsy done just to make sure there wasn’t an underlying condition. Results were negative. I feel completely victimized by this drug. Please, if you love your cat, do not risk using this product!

    30. Dinah | |

      I have two cats, one is 18+ years old and the other is 16+ years old. My 18 year old is highly allergic to fleas and weighs only about 7 pounds. When she was younger, she was closer to 13 pounds until she was about 12 years old. She went through a bout of (something) which nearly killed her. Since then she has had a very sensitive system and is very finicky. She’s in great health, plays and is very affectionate. I gave her Comfortis about a month ago to deal with a flea infestation. Yes, I was concerned about her age, weight and her history. We used the smallest dosage available…(sorry I don’t remember the exact mg)…and she has been fine. It took care of the flea problem and I won’t use it again because I feel if ‘it ain’t broke, don’t fix it.’
      I do use diotomateous (sp?) earth around the house and yard. I also have two dogs with whom I’ve used Nexgard (active ingredient: afoxolaner, by Merial parent company of Frontline). I used the Nexgard one time on both dogs with no ill-effects, so far one month later. Again, I will not use the Nexgard for several months and only if there is another flea infestation in my house. I take my dogs for long hikes in the woods so they pick up fleas and ticks but I treat car, yard and house fairly often with DE and the dogs get bathed with neem oil based flea shampoo prior to coming back into the house.
      My second cat has had one dose of Comfortis the same time as my older cat with no ill-effects so far one month later. He, too, will not be treated again until there is another infestation…IF there is another infestation.
      Last month was the first time I have ever used a pill to treat my animals for fleas. I have, over the many years, used infrequently a topical treatment for all my animals to treat fleas and ticks. Mostly, I use an environmentally friendly treatment for the little buggers. I may leave 6 months between doses. My home has had flea infestations, yes. However, they usually occur once a year around spring. I live in Florida where the fleas never get a die-back due to weather conditions. So, I consider that’s a pretty good track record.
      I don’t know if any of this information is helpful. I hope so. I feel for the pet owners who have administered a medication they believe harmed or killed their beloved pet. The feeling of guilt must be crushing. Just know our pets will meet us on “the bridge” with a happy face and tail up when it’s our time to leave the body because they know we loved them. That’s what matters, forever. Mistakes happen…no comfort in that, I know. It’s good to have these sites when we pet-parents are searching for clues before we administer a drug/product to our precious companions.
      Smiles and Bright Blessings….

    31. Milo's Grammy | |

      I have 2 small dogs that are 14 and 21 lbs and one cat that is 16 lbs. Both my son’s each have a cat. One is 10 lbs and the other is 17 lbs. We take extremely great care of our furbabies and still get awful flea infestations. We’ve also tried almost every flea remedy out there and they’ve all failed miserably. Our 10 lb cat has such bad allergies to flea bites she chews her hair off. Our vet decided to put her on the Comfortis pill and it worked really well. A little lethargic for a day or two but that’s it. We still had bad fleas on the others so I called back and had the rest started. No problems giving it to them. However, my son’s 17 lb cat, Milo, has been very jittery, like skittsy. He doesn’t want to be pet or held and definately let’s me know by biting or scratching me.. He is definately not himself. I am really worried and will be calling the vet tomorrow. He’s the only one that isn’t right. The fleas are falling off dead but I’m thinking we have to look at this the way people look at medicine. Some people have a reaction some dont. Only our pets don’t get to choose and can’t tell us what they are feeling. I’m not sure dosing after the problems gone is worth it. I’ve sprinkled diatomaceous earth on my yard to kill the fleas naturally. That will help too. I’m not sure what my opinion is yet……I think that depends on how Milo starts to feel.

    32. Amanda | |

      If my cat throws up after eating it, does it even absorb into their system? It was only 20 minutes after eating it. I paid a ton for this med and in worried it didn’t even have a chance to do its job.

    33. TruXter | |

      After about an hour and a half, the fleas showed up on top of my cat’s fur. So maybe wait that long before you determine if the meds took.
      Because of the throwing up, I would be calling the vet where the comfortis was okay’ed/sold.

    34. andrew zhao | |

      I gave my cat, a beautiful british shorthair named Howard, Comfortis as per his vet’s instructions. I think over the course of 2 or 3 years we’ve dosed him with comfortis 4 times, whenever he got flea infestations.

      The first two times he seemed to be fine (although he puked after ingestion) and the pills did their job very well, killing fleas and keeping them off for over a month.

      His third dose was effective also but some weeks after that he started eating less and acting lethargic. We’d see him at times crouched in front of his water bowl, staring at the water for hours.

      We brought him in to the vet and they discovered renal failure and a minor heart issue. We got him prescribed food and a medication for his blood pressure.

      After a bit He actually started to get much better and was back to his usual self.

      Then, about a week and a half ago he suddenly got a flea infestation. We called the vet to check if we could dose him with comfortis in spite of his renal failure. The vet informed us that it would be fine. Well we dosed him with Comfortis 1 week ago, and he has fallen into a terrible sickness. He has not eaten since the dosage. He refuses to eat the wet food that he loves. He doesn’t even move anymore. He is so weak that he can barely walk. There is an odor about him.

      I hope my best buddy survives this. He was acting very happy and fine until we dosed him with Comfortis and now he is terribly, terribly sick.

    35. TruXter | |

      I would not have done the fourth. Regardless what the doctor said if I knew the 3rd time triggered an illness.

      I hope your cat gets better.

      Maybe check and see if the doctor gets some kickback for selling the pills.

    36. Amy | |

      I gave my cat Comfortis last night and he died today. He was perfectly healthy & such a sweet boy. If I had done any research and not simply trusted my vet, I would have seen many cases on the web of otherwise healthy cats getting ill or dying after this drug was administered. I hope this helps someone.

    37. Susan Harrington | |

      My cat is so lethargic after being given Comfortis. She has been sick before. If she is sick from this, I will know it is this drug. I pray she is ok.

    38. Shauna | |

      Do not give this to your cats. Comfortis nearly killed my cat.

      In 2014 we had a severe flea infestation and I was told to try Comfortis by a good friend and Vet tech. One of my dogs has had drug reactions in the past so I’m always cautious when trying anything new with any of my pets. The first time I administer a drug I give 1/4 of the dose just to make sure they will tolerate the drug.

      Thank goodness I did this when I dosed my cat with Comfortis. Within a day of giving him 1/4 of the dose, my cat was vomiting, not eating, and eventually started wobbling with his hind legs. I took him to the vet and ran tests. Sure enough, he had gone into acute renal failure. My vet told me his numbers were horrid and I should prepare to euthanize my cat.

      Instead, I took my kitty home. Cried my eyes out and did a little research. The next day I called my vet. We started sub q fluids and added a med to his food. Within 6 weeks my cats numbers normalized. My vet couldn’t beleive it and agrees with me that my cat had a reaction to the Comfortis.

      Thank goodness I didn’t give him the full dose that day. I think it would have killed him.

    39. Crystal | |

      hi Shauna….wow….this could of been me writing about my own cat. He is at the vet as I write this…been 6 days now. What med did you add to your cats food? My kitty is 12 yrs old and has never been sick….until I gave him a half dose of the Comfortis. Now he is fighting for his life!!

    40. Nila | |

      Comfortis Killed my healthy eight year old Maine Coon Muse. I trusted a vet who prescribed a toxic Flea Med that took the life of my beautiful boy. We followed the directions and within hours he was dead. He convulsed and died. I would never recommend this flea med to any pet owner. It is a poison that will kill your beloved pet. Do your research I wish I had, my cat would still be alive if I had.

    41. Crystal | |

      *****Update******* My beautiful Ragdoll Siamese passed away Sunday. He was only 12 and never been sick….until Comfortis.

    42. TruXter | |

      Comments are disabled from here out. This post is in excess of 3 years old and was written for the people who were waiting for Comfortis to produce a cat version.

      Because it kind of is starting to look like either trolls are commenting, or paid smear SEO companies are commenting and I don’t want to be part of that.

      You see more than one opinion, you see more than one belief now, that should be sufficient for you to possibly see what you came to see.

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