It has been reported in the media that Trifexis kills dogs.
As with anything in regards to sensationalism in the media one needs to perform due diligence and not go on one report.
There is the potential with any medication or vaccine that there can be an allergic reaction. The most severe is what is known as an anaphylactic reaction. If it is not treated in time, death can result. While many dogs do well with this product, the most common side effect are vomiting, depression/lethargy, pruritis, anorexia, diarrhea, trembling/shaking, seizures, hypersalivation and skin reddening. Elanco, the manufacturer of Trifexis- suggests to use it “with caution” in dogs with seizures. Dogs should also be tested for heartworms prior to starting Trifexis.
We need to keep in mind that we do not have all of the information in regards to the reported deaths. We do not know the following:
Were these dogs tested for heartworms prior to administration of Trifexis?

How much time elapsed between heartworm test & Trifexis administration?

How old were the dogs?

If they were older, (>7 yr)- what was their true health status?

Had Senior blood panels been done?

How long after Trifexis was administered did the pet expire?

Were necropsies (animal autopsies) performed on the patients who died to truly determine the cause of death?

Since Trifexis is metabolized through the liver, where the liver values OK?

All of these questions need to be asked before anyone can determine cause and effect. IF Trifexis is the cause of the deaths ALL of the patients should have the same signs and post-mortem changes as an indicator.
For the full package insert, click on the link provided.

https://www.elancocentral.com/trifexis-product-label.pdf

Pet healthcare, East West Animal Hospital in Lutz Florida