Trifexis and seizures?

We have a 9 year old dog that began having seizures yesterday. Four in one day, all lasting less than a minute. She’s on meds now and we’re hoping we can get them under control soon. She’s had blood drawn and the results should be back in a few hours. She had zero symptoms prior. Her trigger is going outside to use the bathroom. The walking and moving seems to set her off. Carrying her makes no difference. She sniffs around and then goes into a seizure.

The vet told us not to give her Trifexis again because of the seizures. She’s been on it for years without any symptoms. I gave it to both of our dogs a week and half ago. Now, I’m reading about a link between seizures and Trifexis. Has anyone else seen this? I didn’t know about this link. Several different vets recommended Trifexis to us and it has worked well. Now, I just hope we can get her through this and then worry about what to give her next month. And our other dog? Maybe we should switch him too.

I am quite angry about this right now. It seems that this medicine is made from drugs used as pesticides. Big Pharma proves to be untrustworthy, yet again. I don’t know if there’s another cause, yet, but her age is pretty late for epilepsy and our vet immediately went to the Trifexis, knowing her history. Maybe some other cause will be suggested by bloodwork. We’ll see.

We’ve never had ticks in our area, but this year folks have started to see some. So I was investigating flea/tick products as I’m nervous about Lyme disease, etc. I read about the relationship of seizures and Trifexis and decided I would use Cedarcide topical spray (natural) and not a feed through drug for this reason. I hope your dog will recover!

I’m very sorry about your dog, it’s always so tough when they’re sick, especially when we don’t know why. :frowning:

Fleas and ticks are pests. All preventative medication we use is pesticides. Most (maybe all?) of it lowers the seizure threshold. This has nothing to do with big pharma being untrustworthy–we use low, generally safe doses of pesticides on our pets to prevent infestation by pests.



If you haven’t had issues with this product in the past, it is very likely that it is not the cause of the seizures. Lots of things can cause seizures, including but not limited to brain tumors, Cushings, and other medical issues, as well as things like ingesting poisons (including plants, foods that are toxic to dogs, medications, etc.)

While fleas are mainly a horrible nuisance, the problem with ticks is that they carry diseases with serious health risks. The ticks in my area are so epidemic that it is safer to treat dogs with a pesticide than risk Lyme disease (or other tickborne illness). You have to weigh the risks/benefits; for me the natural sprays are essentially useless. Not if you take your dogs into fields/woods, which I do. So I use the Seresto collar, but it’s not without risks; for some dogs it is a bad choice.


I am so sorry you both are going through this.

My 10 year old dog had seizures as a 3 year old for no reason we could find. Vet put her on meds that I weaned her off of later as they made her a neurotic mess. She had been seizure free until a few weeks ago and she has had 2 small ones. It is just as hard to go through it now as it was then.

I am sure any of the flea/tick treatments we use harbor risks but sadly we need to keep them off our pets. It is a no win all around.

Trifexis caused my Jack Russell to have scary neurological symptoms. She didn’t have seizures but did go “off” in the days following getting the trifexis pill, and it got worse over several months til we put it together. When she couldn’t jump (she jump jump jumps for her dinner, like a little bouncing ball, and barks…the last time she got trifexis, she would just sit and whine instead), was wobbly and off balance, and was looking glassy eyed and out of it, we figured out the connection and our vet agreed. No more Trifexis. We have switched to a topical (Revolution) and not had any bad reactions. My other Jack was not on it very long at the time since we’d just gotten him and he also got a little weird after having Trifexis, not so obvious as the girl, but kind of out of it and not himself. I’m very leery of the feed through ones now, at least for my small (<20 lbs) dogs.

Our sweet girl had one, much shorter seizure this morning. Nothing since. She’s going to stay on the medicine until we work out a plan with our vet. Two vets asked if she was on Trifexis. I wish I had known it was this common. I would not have used it. It’s the same with horses. You have to weigh the good against the possible side effects. If it’s really this common, I would have liked to know that before I started them on it. No symptoms for years means nothing. It can happen out of the blue like this. The local boarding facility deals with dogs under stress. They have seen several dogs have idiopathic seizures. Every dog has been on Trifexis.

Her blood work came back normal.

Our other dog has had a reoccurring rash. We thought it was allergies, but I’m going to stop Trifexis for him as well to see if the rash stops. One other dog had the same type rash in the past. Also on Trifexis and the rash reoccurred. I didn’t know this was a side effect. Our vet never mentioned it either. He just gave us antibiotics during a flare up. The dog with seizures has never had a rash. She had zero side effects until yesterday.

Did you get the Trifexis from the vet? I am thinking it is prescription only so should not be tainted. But products like fake Seresto collars have been sold on Amazon and there is a likelihood that many of the problems associated with that product are really because some are counterfeit, and may have different ingredients.

If both your dogs are experiencing differences from a product that they had previously tolerated well - I would check it out. Sometimes manufacturers change things, even the non-active ingredients, and dogs can react.

That said, the issues may very well be unrelated to each other, and to the Trifexis. It’s an easy target if a dog is on them, but it’s certainly not the only (or most likely) reason for a seizure.

Idiopathic seizures means - by definition - that they don’t know the cause. And idiopathic epilepsy is a horrible and absolutely hereditary issue. So I would take this comment with a grain of salt. I know several great breeders who have had litters produce epilepsy - the common element would be difficult to identify if you didn’t know the whole story – in one case - dogs were between 2-4 years old, some intact, some unaltered, some dogs, some bitches, in different states, in different programs, diets, flea/tick, etc…but the common element was that they were littermates and 5 out of 7 had epilepsy.

Personally, I prefer not to give my dogs a feed-through flea/tick product, but it doesn’t mean that topical pesticides don’t also have risks, including seizures.

The rashes have been off and on for years. We blamed an outside allergen, which could still be the cause, but because it is a potential side effect of Trifexis, it’s worth switching to see if our poor GSD stops getting the itchies.

Our sweet little spaniel has been remarkably healthy up until now. Stress was a suspected cause of the first seizure, but after the second one within hours, the vets started to think of other causes. She had 4 total within 12 hours. She was started on seizure meds before the last one. The following morning, after sleeping well, she had a much shorter one (20 seconds) and recovered faster. No seizures since.

We have always ordered through our vet. I’m not aware of any off brand Trifexis, nor would I trust it.

From what the vets have told us, (I asked very straightforward questions after staying up all night worrying about our poor little spaniel dog and reading internet rumors) seizures can happen out of the blue like this, but in their experience, it happens far more often to dogs on Trifexis.

People who got off brand Seresto did not know it; they were fake. But if it’s being ordered by the vet I’m sure the supply is secure.

Best of luck! And of course I would stop the meds, because why not, but definitely keep an eye out for other possible causes…anything from mushrooms in the yard that may have been eaten, gum, other foods or medicines, etc.

Totally agree here, and in a senior dog, I’d be awfully tempted to radiograph the head as well. Brain tumors often cause seizures.

@moonlitoaksranch do note that pretty much all of the flea & tick preventatives lower the seizure threshhold.

FDA release about Bravecto, Credelio, Nexgard & Simparica

AVMA release about Seresto

Scientific American article about adverse effects, include seizures, and cites Frontline and Advantage

You may not be able to have this girl on any preventative going forward, but definitely skip until her seizures are definitely under control. Glad she is doing better!

Sweet Maddie’s follow up appointment is on Wednesday. We’ll come up with a plan then.

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I am sorry to hear about your sweet puppers. My young at the time Riley would have seizures when I gave him Trifexis at the ages of 4 months and 5 months (bad momma) it took me two doses to figure out the Trifexis was calling the issue.

He put him on Spectrum Plus and he is now 11.5 yrs old.

We recently moved to PA so I switched him to Nexgard due to the ticks up here. He has not had any issues since using Nexgard.

I had called Trifexes when I noticed what was going on and they sent me a check replacing the package I had purchased and advised me to just toss the remaining doses.

My vet did not put two and two together and kept pushing Trifexes (since that is what they carry) for YEARS!!

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I wouldn’t rule out the Trifexis as at least a contributor to seizures. Our Corgi developed a squinty eye. Huge work up and we finally ended up at the UPenn vet school. They suggested could be Simparica. I was frankly dubious but stopped it. Symptom resolved in 6 weeks. I switched to Frontline Plus. Fast forward three years and poor guy gets Lyme. Test was negative as part of squinty eye work up. Now shifting lameness and strong positive titers. Does well with treatment. This spring I switch to Trifexis and within a week the squint is back. Stopped it. Squint gone. Could be a coincidence but I’d have a low threshold to stop this class of Meds for dogs with neuro symptoms. It’s tough because the ticks and Lyme, etc are a real threat.

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Try Nexgard. My now 11 yr old does not have any issues with this formula and he did with Trifexis.

We also used Sentinel Specturm in the past. We moved from FL to PA this Spring and moved everyone on to Nexgard, no issues so far.

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