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Are Comfortis and Trifexis killing dogs?: FDA records 340 dog deaths associated with these drugs.

By Dr. Andrew Jones

Trifexis-for-Dogs-2

There are 2 new drugs in the veterinary market called Comfortis and Trifexis. The company manufacturing the drugs claims they are safe, but there have been over 26,000 dogs with reported side effects, and over 300 dog deaths.

What is it?

Trifexis and Comfortis are monthly chewable tablets for dogs. Trifexis kills fleas and prevents flea infestations, treats and controls hookworms, whipworms and roundworms, and prevents heartworm disease. Comfortis is used specifically for fleas.

Buy-Comfortis-Picture

Trifexis contains 2 drugs: (spinosad + milbemycin oxime). Milbemycin has been used for 20 years with virtually no side effects. Comfortis contains spinosad. The concern is with this ‘new’ drug, spinosad.

Here is what the company has to say about side effects with Trifexis (source: Elanco)

As with all medicines, sometimes side effects may occur. In some cases, dogs vomited after receiving Trifexis. If vomiting occurs within an hour of administration, re dose with another full dose. During field studies, no severe or prolonged vomiting occurred. Additional adverse reactions observed in the clinical studies were itching, decreased activity, diarrhea, inflammation of the skin, redness of the skin, decreased appetite and redness of the ear. All reactions were regarded as mild

The company makes similar claims about Comfortis.

The most common adverse reaction reported is vomiting. Other adverse reactions reported in decreasing order of frequency are: depression/lethargy, decreased appetite, incoordination, diarrhea, itching, trembling, excessive salivation and seizures.

FDA Adverse Drug Reports

The FDA compiles adverse drug reports, and there are a huge number reported on spinosad, the new drug in Comfortis and Trifexis. In going through the FDA reports, I counted over 400 different adverse drug experiences in dogs, and over 10,000 dog owners reporting side effects.

Here are over 40 of the adverse effects:

Spinosad

Spinosad1

Clearly there are serious problems with this drug, and the FDA should be warning pet owners and veterinarians about these potential side effects before more dogs become ill or die.

In the interim I would suggest to not give your dog Trifexis, or dose your dog or cat with Comfortis.

Best Wishes,

Dr Andrew Jones, DVM

P.S. Please forward this to other dog owners you may know.

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Topics: Dog Health, Pet Care, Pet health | 42 Comments »

42 Responses to “Are Comfortis and Trifexis killing dogs?: FDA records 340 dog deaths associated with these drugs.”


  1. Kim Says:
    November 15th, 2013 at 1:20 pm

    Where is the link for FDA’s adverse reports regarding Trifexis? I searched everywhere and couldn’t find your referenced document regarding adverse affected in Spinosad. Could you please share the exact sources and references for this information? Thank you.

  2. Gloria Scott Says:
    November 16th, 2013 at 9:38 am

    My dogs have taken Trifexis for quite some time now…I have noticed itching but that is all.

  3. Tony knighten Says:
    November 16th, 2013 at 3:36 pm

    What would be a good substitute for Trifexis?

  4. teresa bilton Says:
    November 17th, 2013 at 8:18 am

    we have used Trifexis for a year now an love it no prob. an never a flea. also use the collar preventic an never get a tick before using we would pull off 1 or 2 a day

  5. Jason Says:
    November 17th, 2013 at 10:25 am

    I would use Heartgard and a topical for flea/tick

  6. Active vet Says:
    November 24th, 2013 at 7:14 am

    All drugs have side effects and yes ANY can cause death including basic vaccines. But the risk of not useing these life saveing products are much higher. This is a wonderful product that protects a lot of pets from Heartwrom disease, intestinal parasites and other zoonotic disease spread by flea bites. I am truly sorry for anyone that has lost a pet due to medication reactions but talk to a reputable qualified veterinarian about your concerns!

  7. R.D. Minter Says:
    November 24th, 2013 at 11:48 am

    After only 6 doses of Tirfexis one of my Schnauzers starting having GI Bleeding and on examination she had lost most of her Platelets and required 3 blood transfusions and three nights in the Emergency Pet Hospital. In addition, she had to be put on Steroids and almost didn’t survive. Within 30 days our second Schnauzer who was also on Trifexis started passing out and after examination by our Vet. she was diagnosed with inflammation around the Heart and Addison’s disease (lose of her Adrenal Glands). She progressively got worse and died within two weeks from multi-organ failure.

  8. Christina Says:
    November 25th, 2013 at 1:19 pm

    I agree w/ACTIVE VET: all medications come with a risk, even Tylenol for humans. Comfortis and Trifexis both SAVE thousands of pets each month by not allowing them to get too many fleas which may lead to anemia and other blood disorders or heartworm which is very costly to treat and even fatal.

    Talk to YOUR veterinarian, not one online.

  9. Paula Says:
    November 27th, 2013 at 12:32 pm

    PLEASE get your facts correct before blasting them on the internet. I want to see the FDA reports…if the FDA feels this drug is TRULY not safe, why has it not been pulled off the market??? The FDA isn’t making money on it! Oh, and why are you no longer a veterinarian???

  10. Iz Says:
    December 3rd, 2013 at 6:22 am

    The FDA isn’t making any money on pharmaceuticals? Think again Paula. FDA and big pharma are hinged at the hip and although we can file a complaint with them, it’s very unlikely they will respond UNTIL there is a very large number of associated deaths, illnesses or similar complaints- especially when they are being paid incentives by a drug company. Remember Vioxx and how many Americans died before it was banned? Tequin? My gosh, the Vioxx incident alone should have been a wakeup call to Americans to question their trust in the FDA. The truth is that most regulatory bodies in the US today are influenced by the industry they are supposed to be monitoring and regulating. At one time, the FDA really was trustworthy but not anymore dear. About 13 years ago or so, the FDA was beheaded and industry oversight became rather slack in an effort to further support deregulation of big corps including drug companies.

  11. Iz Says:
    December 3rd, 2013 at 6:46 am

    Instead of everyone just being complacent and accepting the fact that drugs have side effects, why not look for safer alternatives that are available? In some cases I have no choice but to use radical medicines and therapies but only when we are absolutely forced to. Alternative therapies in human and animal medicine are often dismissed as quackery, despite studies that demonstrate otherwise, for a multitude of reasons…mainly because the drug companies haven’t found a way to bottle and sell these therapies. FDA tried to shut down the cherry industry because cherries were proven to be more effective in the treatment of gout which competed with expensive pharmaceutical drugs. Why put yourself or your beloved pets at unnecessary risk? My first line of defense is nutrition for myself and my animals. I don’t believe in quick fixes even though they are certainly more convenient because according the first law of thermodynamics, ‘ no one gets a free lunch’ and so we pay a heavy price for conveniences like cheap fast foods, laziness and apathy, quick fix medications that only suppress symptoms without addressing the cause, etc.. Always question authority and do your homework.

  12. Andy D Says:
    April 17th, 2014 at 5:42 pm

    I myself do not trust Big government.They keep proving time and time again that lining their pockets is more important than our well being.Just type in FDA scandal and see what comes up, or try conflict of interest. These drugs for the most part are fast tracked with minimum research. Fast tracking was pushed through by the lobbyist. And the bean counters tell them what the potential risk is and they bring it to market. If you think otherwise your kidding yourself. This stuff will not go on or in my pets.

  13. Suzanne Says:
    June 2nd, 2014 at 8:08 pm

    This is my personal opinion but even before reading this article I refused to give any of my 3 dogs any flea preventative that they have to ingest. Personal choice and the people that have made the decision to treat their dogs with Trifexis and have had no side effects that’s great. No need to get defensive about the report. I believe that it will cause long term effects. I would rather use a topical which isn’t all together that healthy either.

  14. Holly Aydelette Says:
    August 4th, 2014 at 5:13 am

    We gave our dog Trifexis and he immediately started scratching. I agree with one lady; if they have to swallow flea medicine forget it! I tend to not want to try the new stuff and wait to see how it turns out before trying it.
    Say yes to trusted medicines!

  15. Tina Spears Says:
    August 11th, 2014 at 3:53 pm

    Very Concerned!! First dose of Trifexis given to my 132lb German Shepard last Wednesday, he vomited during the night. Saturday he had a seizure that lasted 5-10 minutes. It was horrible. I just spent $350.00 on Trifexis last week, and after everything I have read today, it’s going in the trash. Hopefully, my Shepard will not continue to have problems

  16. Mike Says:
    September 3rd, 2014 at 4:22 pm

    Our hearts are consumed with pain. We just lost our beloved dog Crown this morning. He was a very happy and extremely healthy 4 1/2 year old pup. We had taken him to the vet on 12 August for his checkup, and he received a clean bill of health. During the visit we needed to get him more heart worm preventative, usually heart guard, but the Vet convinced us of the benefits of Trifexis. He received his first dose of Trifexis that afternoon. During the time since then he seemed a little more sleepy and less playful, but we didn’t think too much of it at the time. He wasn’t sick and ate just fine. This morning we awoke to our sweet, active, loving and overly playful boy not coming to greet us immediately. We found him on his favorite spot looking to be asleep. When we tried to wake him he didn’t respond. He had stopped breathing. He was still very warm and looked to be in a deep sleep so we rushed him to the Emergency vet and they pronounced him dead.
    I am only now aware of the dangers with this drug and it is too late. The only thing that he had taken differently was this medication. He was extremely active and had a very good diet. He was 36 pounds and pure muscle. My family has been completely devastated by this.

  17. Pat Potesta Says:
    October 24th, 2014 at 2:05 pm

    I switched over to Trifexis several months ago. My dog goes to Banfield twice a year for his comprehensive exam. Always left there with perfect health care, until this last visit. My dog has developed a heart murmur. The vet says it’s common in that type of breed. I don’t believe them. The only thing I’ve changed in the last 7 1/2 years is his flea medication. I switched to trifexis at their recommendation. BAD MISTAKE…………….. I believe it is the trifexis. Now I have a sick dog.

  18. Lauren Says:
    March 6th, 2015 at 6:05 pm

    Trifexis killed our healthy lab Duke. THANK YOU DR. JONES so very much for having the courage to flag this issue for your patients, to speak up against the Elanco/FDA machine that allows more dogs to be killed every day.

    Every day it hurts to know we gave Duke the pill that kill him just hours later. I am extremely skeptical of the numbers that are being reported because our vet and we definitely reported Duke’s death to the FDA as related to the Trifexis we gave him the morning he died. They never acknowledged it. No doubt there are thousands more dogs that died this way that have not been reported.

  19. Dawn Says:
    March 8th, 2015 at 11:49 am

    I have never had any real issues with comfortis. We have never used trifexis. The only exception was a rescued blind/deaf lethal white cattle dog that we pulled from a kill shelter. However, certain types of cattle dogs, collies, shelties react to heart worm preventative and flea meds differently than other breeds of dogs. I gave the little dog comfortis and he started vomiting and it caused an ulcer in his colon and to have bloody stool. With quick treatments we managed to help him. There are warnings on the box. I think his system was in a weekend state to begin with and I messed up giving him the pill. He was my first and only one to have a reaction. All mine get comfortis here. I can’t use frontline because 2 of them have a reaction to frontline as well as advantix. One reacts to flea collars. One reacts to heart guard.

    We just bought sentinel for the dogs. We have not given it to them just yet. Almost kind of scared to.

  20. Pam Says:
    March 8th, 2015 at 10:48 pm

    My friends Australian Shepard started having having seizures shortly after taking it. She stopped using it and had not had another one since.
    My dog gets comfortis (for two years now)and has not had any issues but this article is alarming

  21. ruth mills Says:
    March 16th, 2015 at 7:50 am

    It was ubsequent to giving a dose of Comfortis on same day as a rabies shot to my 13-year old Chi in 2012 that her health began deteriorating. (I have read since that the 2 things together can overwhelm the adrenal system.) She was diagnosed with Cushing’s disease, and within 9 months she was so irreversibly ill we had to have her put down! I have bought Comfortis since for my other 2 dogs, but after giving one dose was to afraid to do it again! I’ll just get them checked a couple of times a year for heartworms and do as much natural flea/tick prevention/treatment as possible!

  22. Glanda Widger Says:
    March 16th, 2015 at 1:08 pm

    In response to a question about why the FDA does not take this drug off market. For the same reason vets still prescribe previcox which causes an adverse reaction in 3 out of five dogs and death for at least one in 5 . Because it is a dog and not a human and profit margin..If you want to see reports about effects you can usually go to the manufacturer’s web site as they are required to publish any adverse findings. That is where I found the previcox information. Not every dog dies or if they do the owners do not report it as a reaction because they do not know.

    I stopped giving my beloved pet any prescription’s after he almost died from one dose of Previcox and I sure would not give him any new medications on the market. If even one in 5 animal dies, are you willing to have your pet be that one? You may have good luck with a product but it is not worth my pet’s health or life to try it.

  23. KimZ Says:
    March 16th, 2015 at 2:01 pm

    For those of you looking for the FDA reports, here’s a link:
    http://www.fda.gov/downloads/AnimalVeterinary/SafetyHealth/ProductSafetyInformation/UCM055411.pdf

    Scroll to page 418 for the report on the combo of Spinosad and Milbemycin
    and page 430 for Spinosad

  24. bakbrakr1 Says:
    March 16th, 2015 at 3:51 pm

    My dog had a benign lipoma. 2 weeks later during pre op, the vet offered to do her shots then instead of having to come back in a few weeks later. Not knowing any better, I agreed. Almost immediately, her tumor started to grow from about the size of a grape to the size of a tennis ball. When she went in for surgery 2 weeks after shots, the benign tumor metastasized throughout her entire reproductive system, urinary, colon and rectum. She only had days to maybe a couple weeks to live and was so far gone, they said chemo would do nothing but cost $. It wouldn’t help her.
    I mourned for 2 days then came back fighting. I researched cancer til my brain felt like it was in a blender. I switched her to raw food and some well researched herbs.
    In 5 weeks, her tumor shrunk from the size of a tennis ball to the size of a walnut. Vet couldn’t believe it. Said the “tendrils” were gone. Thought the cancer was gone. I asked her if it was safe to administer comfortis with her issues. She said it was. Within 6 weeks her tumor was to the size of a softball!

  25. Linda Root Says:
    March 16th, 2015 at 4:37 pm

    Comfortis killed my 5 year old dog, Twinkie… My vet. quit selling it, She was shocked how many clients pets were having problems with it.

  26. mima Says:
    March 16th, 2015 at 6:41 pm

    The statistics are guaranteed, WAAAAYYYYA higher than reported here. Too many owners like myself, simply stop using it with out reporting. My dig was vomiting and acting sick so I stopped it. Went online and sure enough found soooo many complaining about the drug, but most of those are unreported.

  27. mima Says:
    March 16th, 2015 at 6:45 pm

    I should have specified that in my case, it was the Comfortis.

  28. Debbie Says:
    March 16th, 2015 at 8:27 pm

    My dog had been on this for a short time .. He started vomiting right away and having convulsions and had to give him mouth to mouth ..called the company after talking to the dr. They said we have no reports like yours . ..it’s perfectly fine … Jerks

  29. kaleba Says:
    March 16th, 2015 at 9:09 pm

    I asked my vet about Trifexis. He said there is absolutely no evidence that Trifexis causes any harm to dogs. He said that dogs got sick and their owners didn’t know why, so decided it was the Trifexis. They put it out over the Internet, and the rumor spread from there. He says he gives his own dogs Trifexis and they are perfectly fine. He wouldn’t give his own dogs something that would harm them, would he? I think not. On the other hand, he could be lying to me. He probably gets Trifexis from the manufacturer for free in exchange for selling it to his patients, thus he has a financial stake in convincing his customers that Trifexis is safe. So what’s a person to do? I want to try Trifexis because the drops I was using for fleas seem so toxic and awful, plus of course he needs heartworm medicine. Trifexis seems like a perfect solution. But I love my boy, and if anything ever happened to him, especially due to something I gave him, I’d be crushed. I’d never recover.

  30. Lori kerrigan Says:
    March 16th, 2015 at 9:41 pm

    I can not read anymore as its making me sad hut, one things for sure I WILL NOT be giving either of these medicines to either if my dogs. And to Paula who said about wanting to see the FDA reports first why would you even risk your dog’s life if there was a possibility of these medicines causing death in your dog. I would rather bathe my dog with flea shampoo everyday rather than risk their life even if there was only one death reported hell even if one dog almost died because of the drug or it was possibly the drug. I don’t know what you think about your pets but mine are family my children to be exact and I would rather have been inconvenienced first than take a chance of losing my beloved animals. And I agree 100% with those who spoke honestly of the FDA stating they are at the hip with pharmaceutical companies. Sorry for the loss of anyone who lost a loved one due to these drugs.

  31. Linden Vet Says:
    March 16th, 2015 at 11:56 pm

    We are looking into it and will give feedback shortly.

  32. Heather Sharkey Says:
    March 17th, 2015 at 5:41 am

    My male Leonberger had a lot of these side effects the first time I used Avantix tick and flea treatment (not seizures though). My female had no side effects. Now I use an organic spray on both of them. Probably not as effective, have had a couple of ticks, no fleas BUT NO side effects. My vet tried to get me to use Confortis instead, but I have never liked the idea of regularly given my dogs chemicals to ingest. I spray them every time they go out.

  33. Comfortis and Trifexis - Golden Retrievers : Golden Retriever Dog Forums Says:
    March 17th, 2015 at 6:11 am

    […] Here is an interesting link regarding "side effects" of Comfortis and Trifexis. Is Trifexis killing dogs?: FDA records 340 dog deaths associated with Trifexis. | Veterinary Secrets… __________________ Jane Four Lakes Goldens Four Lakes Touch The Sky "Piper" – the new […]

  34. Dennis Says:
    March 17th, 2015 at 6:35 am

    I have been giving my Westie, Deuce, trifexis for about 8 months now with NO ill effects. I make sure he eats the pill with a good helping of food…he has not had any noticeable side effects. He weighs about 21 pounds and takes the entire dose, which I was hesitant to give him at first thinking such a large pill must be for larger dogs…but he was fine.

  35. Yvonne Newton Says:
    March 17th, 2015 at 7:10 am

    I won’t use chemicals without complete necessity! Encourage any breed to use WaggleAntics- a natural tick defence. Can be found at http://www.waggleantics.co.uk

  36. gloria Says:
    March 17th, 2015 at 1:20 pm

    Please let us know what you recommend for fleas and Ticks

  37. gloria Says:
    March 17th, 2015 at 1:24 pm

    PS Frontline failed in Florida !!After 9 years of no fleas she was loaded !!

  38. Darlene Says:
    March 17th, 2015 at 5:50 pm

    I have used Comfortis for two summers now, and always with worry and trepidation. Feeding insecticide to my dogs, whom I love with all my heart, worries the hell out of me. The other resources we had to choose from would last at most 2 weeks, which led me to take these great chances. The only thing that gives me the least bit of comfort, moments before giving it to my dogs I feed them a concoction of cooked rice and cottage cheese, full bowls., with intention to line their stomachs rather than the dry crunchy dogfood they usually eat. Also, I insist on giving them the dose suggested for a smaller weighted dog. For example, my Luca weighs 65 lbs, he takes the one for dogs 40-60 lbs. and my Remy ways 42 lbs. and he takes the one for 20-40 lb dogs. I think part of the problem is they are overdosing these dogs. Mine have never even had a minor side effect. Am I still leary of this product, oh yes, but with the infestation we get, it is the only thing that has been successful. I live in Indiana, our summers can be a brutal attraction for fleas, I only treat them June-Sept., sometimes I stretch dosing it to 5 weeks apart. Most important, I do not follow Elanco’s recommendation regarding Comfortis. A little goes a long way.

  39. Karen Diamond Says:
    March 19th, 2015 at 11:15 am

    I have a vet who unequivocally refuses to prescribe spot on flea treatments saying many of his clients have lost all their fur from them. Nevertheless, he recommended Confortis for my small dogs, but only at the smallest size and 1/2 dose at that. I gave it to my 7 and 12 lbs dogs and only noticed an immediate end to fleas, no bad side effects. Nevertheless, I’m still leery of giving it to them again. I won’t use spot ons because the fleas have become immune to them here (no. Ca.), but have found shampoos do nothing act all. I’ve asked several vets who are my friends and the’ve ALL said they use Confortis. Any real suggestions for flea killing that don’t harm a lot of dogs?

  40. Dee Says:
    April 13th, 2015 at 9:11 am

    My doodle puppy was violently ill after taking this one time, i knew it was wrong !! I reaearched and found a natural spray that works and can use it on my grandkids withno fear or guilt . If something seems too good to be true – IT IS !!Avoid using it,

  41. rod hewitt Says:
    May 20th, 2015 at 5:36 pm

    My Belgian Shepherd lived most of his life with near immortal power, his strength, speed and resilience have amazed though who have seen him. Two and a half weeks after adnministering trifexis a dog that had a vertical leap higher than Kobe Bryant could hardly get into a car. Realizing at that point that there was something amiss I researched anf ound that Trifexis was indeed the culprit. After consulting with the lead veterinarian at that company, despite her sympathetic approach, I was aware that there was no known antidote for what was taking place. Within a day, with the help of a few brilliant homeopaths, I put Achilles on Milk thistle, dandelion oil and an amazing product from BIOAGE that has been developed for animals. In just three days the symptoms started to reverse and in three weeks he had returned to health. I believe that this criteria will work in reversing this terrible condtion

  42. Shea Says:
    June 8th, 2015 at 4:11 am

    My small terrier mix has taken this around 3 years with no side effects besides it possibly caused her 2 small lipomas. I have one dose left to give her and after that looking for something else. I might go back to triheart for heartworm preventative and comfortis or heartgard for flea preventative. She’s never had a problem with fleas and we are in the south where fleas are prevalent. She goes outside for occasional walks and out to potty. Any suggestions for a small mostly indoor dog to take that’s safe?

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