No correlation found between Trifexis and animal deaths


The Food and Drug Administration has found no link between the recently reported dog deaths and the drug Trifexis by Elanco. Drs. Randy Beck and Jordan Mracna, veterinarians at South Cherokee Veterinary Hospital, claim there is no correlation as well.

“The FDA has done all sorts of rigorous testing and all sorts of interviews, and still to this date, at least to my knowledge, there has still yet to be a single death of any dog reported that has been because of Trifexis,” Beck said.

Dr. Jordan Mracna (left) with Dr. Randy Beck (right) in their South Cherokee Veterinary Office. Photo by Taylor Cunningham.
Dr. Jordan Mracna (left) with Dr. Randy Beck (right) in their South Cherokee Veterinary Office. Photo by Taylor Cunningham.

In November 2013, WSB-TV reported a story about dog owners claiming that the flea, internal parasite and heartworm preventative, Trifexis, caused the death of their animals. WSB reported again on Trifexis in July 2014, this time with the death complaints being increased by about 40 percent.

Elanco released an official statement in July 2014 stating that both the company and the FDA are doing continuous monitoring of Trifexis and other products, and that there has been no scientific evidence that the drug is the primary cause of fatality among the reports from owners.

These reports are considered owner-reported deaths to the FDA, and according to Beck should not be considered as substantial evidence that Trifexis is the cause of any of the reported deaths.

“Because it’s an owner-reported death, in no way, shape or form does that mean that it truly was caused by Trifexis. In order for it to be considered a death caused by that drug, there has got be some kind of authoritative figure or qualified person to say that it was,” Beck said.

Necropsies were performed on three of the dogs whose owners claimed died from Trifexis mentioned in WSB’s news report. Their necropsies indicated that their primary cause of death were heart-related ailments such as endocarditis and myocarditis.

According to Beck these ailments were not seen as any symptoms during the testing and trials of Trifexis prior to its release on the market.

“The only adverse reactions I’ve ever seen is some mild gastrointestinal upset,” Mracna said. “Occasionally some dogs will vomit up the pill after they take it, that being only one incident and they are fine after that. I’ve never seen anything worse or fatal by any means.”

Trifexis is the combination of two active ingredients: milbemycin, the heartworm preventative and spinosad, the flea preventative.

“The spinosad tends to be the one that is a little bit harder on the gastrointestinal tract and causes some stomach upset and things like that,” Mracna said.

According to Mracna the most likely way Trifexis would be fatal would be from an inappropriate dosage given, such as a pill for a large dog, or even just a part of it being given to a small dog.

“I don’t think the medication itself, if properly dosed and administered, would cause any problems,” he said.

Both Beck and Mracna agree that Trifexis is one of the most effective preventatives on the market.

“Most people like the fact that it is an oral product so you don’t have to deal with the messy topical type stuff, and people don’t have to worry about it getting washed off with baths or swimming and things like that,” Mracna said.

“It has become the number one heartworm and flea preventative for this clinic and for many clinics that I know without incidents,” Beck said. “My own dogs take it.”


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