• Blog >
  • Trifexis Safety Concerns
RSS Feed

Trifexis Safety Concerns


Some of you have been directing emails and phone calls our way after grieving dog owners blaming Trifexis for the loss of their pets have made news headlines. Many of you currently administer Trifexis to your dog(s) monthly to prevent heartworm, intestinal worms and fleas at the recommendation of the doctors and staff at La Costa Animal Hospital.

Three of the deaths that made news headlines were those of three littermates, all Vizslas, who died after receiving their first dose of Trifexis. Two died within three weeks of their Trifexis dose, one died six days later. The cause of death of all three dogs was determined by an independent pathologist to be heart disease and unrelated to Trifexis; two appeared to have died of a bacterial heart infection, the other was likely born with a diseased heart. Though it seems an unlikely coincidence that the other littermates are alive and healthy, these three dogs were apparently healthy up until the moment of their deaths.

The pathologist’s report can be viewed here:


There have been other reports of canine deaths after the first dose of Trifexis. Though these cannot all be discussed in detail, and some may truly have been severe allergic reactions (anaphylaxis) to Trifexis as can occur with any medication, the majority were likely due to other diseases.

The American Veterinary Medical Association’s response to this topic can be viewed here:


It is La Costa Animal Hospital’s position that while the death of these pets is certainly tragic, there is no evidence that Trifexis was in any way to blame. The staff and doctors will continue to recommend Trifexis for many of our patients. Elanco, the manufacturer of Trifexis, has established a hotline (888-545-5973) to answer questions pet owners may have. Please note that drug reactions are most likely to occur after the first or second dose of any drug, not after months to years of safe treatment. Please also note that all Elanco products are veterinary only; this means that any Elanco product available through an online retailer may be counterfeit.

There are numerous other flea and heartworm prevention options available. If you would indeed like to consider an alternative product for your pet, we would be happy to discuss these options with you.

With warm regards,

The doctors and staff of La Costa Animal Hospital