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Claim:   Trifexis brand parasite prevention tablets have caused the deaths of a large number of dogs.


Example:   [Collected via e-mail, November 2013]

Trifexis medicine, which is a tick and flea preventative, has been noted it could kill your dog or cat. This was reported in Atlanta. Please check his out if it is true or false.

Origins:   In November 2013, Atlanta television station WSB reported a story about dog owners in Atlanta (and elsewhere) claiming that Trifexis brand parasite prevention tablets had caused the deaths of their pets:
Grieving animal lovers across the country are coming forward blaming a popular pet drug for killing their dogs.

"It's like a piece of your heart is being torn out," said dog owner Beth Timms from Gainesville.

Her dog, Gizmo, died after taking Trifexis. The once-a-month pill made by Elanco is a combination pill for heartworm, parasites and flea prevention. (Elanco is the animal health division of pharmaceutical giant Eli Lilly.)

Timms emailed consumer investigator Jim Strickland after finding a Facebook page titled "Trifexis Kills Dogs."

Owners from all over the country have posted on the page, blaming the drug for their dogs' deaths.

However, WSB noted in a follow-up report that a pathologist hired by Trifexis had found no causative connection between the deaths of dogs who had reportedly died after being given Trifexis and the drug itself:
Consumer investigator Jim Strickland obtained documents from a pathologist hired by drug maker Elanco that said three puppies did not die from taking the drug Trifexis, made by Elanco.

"Trifexis played no role in the death of this dog," Dr. Jeffrey Engelhardt wrote.

In the case of three dogs, Engelhardt said Trifexis' involvement was unlikely. The dogs died of heart failure in September [2013].

Engelhardt did not examine the dogs' remains, only their pathology reports.

The three [dogs] that died had one dose of the drug and became weak and lethargic. Two of the dogs died three weeks after taking the pill. One died in six days.

"We have not been able to identify with all of these reports, any specific trends we can link directly to the use of the product," said Elanco veterinarian Dr. Stephen Connell. "Certainly we want to investigate these cases. We want to get to the bottom of this as much as anyone does."

Elanco insists any side effects are mild, not fatal.
Necropsy reports on three of the dogs mentioned in the WSB news report as possible Trifexis-related deaths (Bishop, Tucker, and Jade) indicated that the canines died of heart-related ailments (myocarditis and endocarditis).

Veterinarian Doc Cleland also posted on his College Park Vet blog that he had not seen any studies indicating a positive correlation between Trifexis and death in dogs and that he would continue to use and recommend the product:
I've seen and heard a lot of concerns over the past several days about Trifexis and how it kills animals. I even visited the "Trifexis Kills Pets" facebook page and looked around there. ELANCO has sent us a fax about their stance on Trifexis. So where do I stand?

Plenty of animals receiving Trifexis die. However, plenty of animals receiving love and attention from their families also die. What has to be present with any medication
or situation is a positive correlation between (a) and (b). If animals receiving Trifexis causes more deaths or problems than animals without, then there is a positive correlation between Trifexis and death. Cause — effect.

With that said, I have not seen any studies to point to this positive correlation between Trifexis and death. ELANCO itself reports an increase in upset stomach in animals receiving Trifexis, and they warn that seizures may be positively correlated with Trifexis. However, there have been no other patterns of adverse events noted either before or after Trifexis was released onto the market. Correlation is everything.

Will I continue to use and recommend Trifexis? Yes.

Are you crazy if you don't use Trifexis? No. Make sure they are on some form of heartworm and flea prevention. I would also recommend that you educate yourselves with information, studies, side effects, and evidence based medicine for whatever product you choose.
Last updated:   18 November 2013

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    Cleland, Doc.   "Trifexis: Killing, Correlation, and Cost/Benefit."
    The College Park Vet   12 November 2013.

    WSB-TV [Atlanta].   "Grieving Animal-Lovers Blame Pet Drug for Killing Dogs."
    12 November 2013.

    WSB-TV [Atlanta].   "Company Insists Flea Drug Not the Cause of Dog Fatalities."
    12 November 2013.