Scary Comfortis Reaction

elizedwardsJanuary 11, 2010

Had been looking all over online to uncover the reason behind my dog's shaking, seizures, and lethargy after taking Comfortis.

Anyway, my 1 1/2 year old field english setter began convulsing approx. 8 hours after taking Comfortis. We took her to the emergency vet and long story short, after x-rays, IV, bloodwork, and under watch at the clinic, she seems to have recovered (this was x-mas eve).

The emergency vet called Lilly Pharm. for more info and got a case number for us which means our case will be sent to the FDA. So definitely call Lilly and talk with their vet--that's the way the FDA will know about it (legally they have to report issues)

Also, our dog was not on high does invermectin yet still had the side effects attributed to the symptoms that accompany the interaction of these two drugs.

We just got her bloodwork retested (it's been a few weeks, and she still has elevated livery enzymes which could be the result of comfortis.

Anyway, just sharing, and so so sorry for those who lost their pets.


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The subject of Comfortis has been discussed here before and it's probably due for a re-run!

Sorry to hear what your dog went thru but I do hope she fully recovers.

As you've discovered, there are many testimonials as to why one should not give this oral drug to their pet.

Here is a link that might be useful: Previous thread

    Bookmark   January 11, 2010 at 5:19PM
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Both of our dogs have done well on this medication, with no side effects (and no fleas).

Very sorry to hear that your dog had such a bad reaction, and I hope she makes a full recovery soon.

    Bookmark   January 12, 2010 at 12:29AM
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I was very afraid to give my dog Comfortis. Unfortunately Advantix and Frontline barely worked when I did not have a flea problem.

I just moved and the woman that lived in my house was a pig. Literally. The house was infested with fleas and roaches. The woman had six dogs who I hear she kept locked up because they had fleas and were "bad" dogs.

1 day after moving into the house (we were unaware of the problems beforehand), my poor dog was infested with fleas.

I did not have much faith in advantix or frontline because when I took my dog to the park she would still get a flea or two on her and the meds did not work to kill the fleas although I am sure they helped to stopped an infestation through eggs.

Anyway we finally tried the Comfortis. Literally within an hour I saw the fleas start to surface and drop off my dog. Even now a few days later, when we see a flea on her it seems to be dying. The product is amazing. I'm not sure I would keep her on it, once we get the problem under control. (We've already had the yard and house treated, and have a repeat treatment in a week.) But I am glad that I tried the product despite my fears.

I am sorry for your dog. But many dogs have reactions to the various products out there. The best thing is not to have to treat your dog. But without Comfortis, my poor dog would be miserable right now.

I was very much against Comfortis, very very against it. (As a matter of fact I remember the original post linked above and thats partly WHY I was so against it) My husband wanted to try it about a year ago when we saw the occasional flea on her and I would not allow it. The ONLY reason I did so now was because the infestation was so bad. Within the first hour of comfortis I got no less than 40 fleas off of her. Its been a week and so far no reaction.

    Bookmark   January 13, 2010 at 10:51PM
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Really sorry to hear about the pets with the problems. I have a 10 wk old boykin spaniel and just took him to the vet yesterday and he was eat up with fleas from the dam and other pups. She recommended confortis and I said sure, so I gave him the tablet and about thirty minutes later bathed him, the amount of dead fleas floating in the tub was amazing. This is the most awesome product I've ever seen! I really hope it's safe but I'm thinking maybe now that the problem is under control I may use something different next month. I read that advantix isn't any good, I'm also new to all of this so can anyone recommend the best product for fleas? Also it doesn't take care of ticks either, what's good for that? Thanks and again it's scary to read that about the dogs. Hopefully they'll improve it and lose the side effects. It is great flea killer however! My pup seems fine but I'm keeping a close watch on him.

    Bookmark   May 31, 2011 at 1:13PM
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My dog Gracie has never had fleas until a couple weeks ago we found two on her and decided to find a treatment.. my vet recommended Comfortis... within 48 hours she began to slow down and not want to eat ( she usually dives into the bowl before we finish pouring her food ) soon the vomiting began.. we took her to our vet and he gave us some suggestions to get her to eat such as chicken and rice. she will not eat,except for a bite or two...not drinking much water either I am so afraid she is getting dehydrated.. she continues to throw up and be lethargic.. I plan to haul her back to the vet on Monday.... I would NEVER give her this medication again... my vet did call the maker of this med. to report Gracie's sickness...

    Bookmark   June 12, 2011 at 9:29AM
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I used comfortis last summer cause we have never had good luck with the other name brands when the dogs are young and active. I had been using another combination of product with some success but the vet offered comfortis. It worked great and thankfully we had zero side effects. I guess we gave the 3 rounds that come in the package and we have not treated for over 6 months and the dogs are still flea free. So I will use this product again for sure but will make sure I don't overdose and if I don't have fleas I will wait till the product is needed. I am so happy that they have something for these dogs. My poor Ziggy runs and hides when a flea bites him.

    Bookmark   June 12, 2011 at 11:11PM
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I live in Florida which seems to be the flea capital. I used to use Advantage, but it seemed to become ineffective. Because I don't have a yard I have to take her to the park. She was just loaded with fleas and seemed that there was nothing that worked until I used Comfortis. Thankfully the Comfortis worked immediately and with no adverse side effects.

    Bookmark   July 1, 2011 at 9:17PM
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My dogs have both been on Comfortis a year or more now. Made the switch because other things were not working and we were having bad skin issues on our lab. I'm sorry others have had problems, but I've been through the 4 digit spending on trying to control the buggers too. There is probably no drug that can be given to all without some having a reaction. It's a shame we can't know what will set of who.

I wanted to post about Over and Out. Ortho sells it here for fire ant control. It's a once a year granular application and it seems to do the trick not only on fire ants but also on fleas. We tried it because my son has had terrible times with fire ants, my dad is allergic and my aunt nearly dies from them. I don't pay an exterminator and don't buy bug spray (in Texas! LOL) but we do that one bag a year on the lawn. We weren't having trouble with fleas when we were hearing from other owners at the dog park and the vets that it was a terrible year for fleas. Sounds like that and cutting back to less frequent doses of Comfortis might be the answer.

    Bookmark   July 19, 2011 at 1:10AM
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I think everyone needs to consider the fact that not all dogs are biologically the same, just as there are differences in humans and every other living species. As with humans, there are times when a small amount will unfortunately have a bad reaction to a medication or vaccine BUT that does NOT discredit the value that medication offers to the masses.

I have used Comfortis for over 5 years on my own 3 dogs (beginning as young as 4 weeks) AND our 2 cats, along with literally hundreds of foster litters, pups, kittens, dogs and cats over the years. NOT ONE of them has ever had a reaction of any sort.

I think the most important issue is not overdosing. Since the tablets come in a pretty big range for weight, it can be tricky. Plus it is often sold in kg packaging not lbs so it might not get converted correctly. If your dog is 38 lbs some round up to the 40-60lb tab thinking it will be more effective, DONT. Also some pet owners "think" they know how much their dog weighs and accidentally overdose. Make sure to weigh your dog before each and every dose!

Also this needs to be given with a meal! So those who suffer with nausea and vomiting, it could be they didnt eat enough after. That could also be partly why others had such a bad reaction. Even humans can have a bad reaction one time and not another to the same medication if not taken properly. For me on the day I am planning to give it to them I take away the free feeder food bowls and give them Comfortis in the late afternoon. Then I immediately give them a BIG meal of their food mixed with a generous helping of canned food to entice them to eat it all. It is the only time (unless sick) they get canned food and see it as a big treat.

Human error aside, like I said before, there are a small number that simply have a bad reaction. I can only pray it will never happen to me, however that fear of possibility is not going to stop me from using it for the benefits outweigh the possible risks. So I am responsible about it. I make sure I will be available during the 1st 24 hrs after giving it to an animal for the first time and have several emergency vets that I can run to at a moment's notice. Because of that I am blessed with a blissfully flea free home despite the barrage of animals that are in and out of it.

For those that are scared to try it because of what "could" happen, I urge you not to. The topicals are MUCH worse in my opinion because they get everywhere and are only half as effective. My daughter who was 2 at the time ended up in the ER because she had gotten some of the topical (Frontline) in her mouth while at a friend's house. We knew he had just been treated and were intentionally keeping her away however the dog got in from the yard and ran straight for her. The contact was less than 30 seconds but given her age, it was enough. We washed her up and didn't think much of it at the time, but 5 hrs later she was in the ER with seizures. Again this could have been an issue of her reaction being "one of the few", we dont know for sure but do know we will not expose her to it again at any age, just to be sure. I would much rather an oral medication that stays where it needs to be, in order to be 100% effective, rather than on that is transferred to other objects and therefore the potency is diluted and less effective.

I have never posted on this site before but saw this when I googled comfortis - getting ready to order more - to see if there were any deals right now. The ONLY negatives I have with it are the price which I grudgingly pay because it works so well, the smell which to my sensitive nose is near toxic, and the fact that I have to shove it down the throat of every one of my animals because none of them like the "beef infused" flavor. Personally those are all things I can live with to get the great benefit it provides.

    Bookmark   October 7, 2011 at 5:52PM
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I have two Chesapeakes and I'm thinking of using Comfortis because the topicals (Frontline, Advantage and Advantix) just don't seem to be working anymore, plus they're giving my male Chessie bad flaky skin problems. I'm concerned about the side effects, so I was wondering if splitting the pill in half or quarters and feeding at maybe hour intervals after a heavy meal would be better instead of the entire pill at once. Has anyone tried that with luck?? I'm also thinking of not redosing until fleas return.

    Bookmark   October 23, 2011 at 2:00PM
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I am a professional dog trainer by occupation, and have been a strong advocate for the BARF diet and natural remedies for illnesses of dogs for many years. However, like many people who have posted problems with heavy flea infestation, nothing worked well for me on my dogs - and I have over a dozen from minies to Timber Shepherds. My daughter resorted to comfortis out of desperation with the little ones a couple of months ago, and the change was dramatic for the better. As result as from a few days ago I've put two of my Timber Shepherd's on it as well. I should mention that my dogs get a daily dose of Zeolite and diartomaceous earth, both products known to remove metals and toxins from the animals (and humans) bodies. Perhaps these products have eleminated any harmful toxins delivered via the comfortis from the animals bodies, and the aspect toxic to fleas has prevailed. In any case, the little dogs are now looking great instead of ratty with bare patches, and clearly much happier. The dogs also get large doses of vitamin C regularly which may also help support the dogs systems.

    Bookmark   June 5, 2012 at 6:19AM
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