Nov 20 2013

Safety Concerns Regarding Trifexis Heartworm & Flea Preventive


Trifexis Logo

Today I spoke directly with Elanco, to determine the facts behind the recent negative stories about Trifexis.  Following this discussion, Elanco made available copies of the independent necropsy reports (when necropsy was performed), for the dogs reported in the news media as having died from ingesting Trifexis.  The pathology reports clearly conclude for each animal that “Trifexis did not play a role in the death of this animal”.    Other, underlying medical conditions appear to have been the actual cause of death in these animals.

Over 50 million doses of Trifexis have been sold and while adverse reactions are reported, FDA accepted safety studies indicate an adverse reaction rate of less than 1%.  This is consistent with label claims. As of today’s date, no animal’s death has been confirmed to be related to Trifexis.

Elanco makes no secret of the fact they purchase their Milbemycin (a component of Trifexis) from China.  This drug component undergoes comprehensive safety and potency testing prior to leaving China, upon arrival at the manufacturing plant, during production, and post production.   At no time during any of these testing procedures has any concerns regarding safety, efficacy or potency of the drug been noted.

The most typical side effect we have seen during use within our hospital is transient vomiting post administration.  This is a listed side effect of the medication and is not considered life threatening or harmful to the long term health of the patient.  We have not recorded any other types of reaction to Trifexis in the 3 years we have been prescribing this drug.

We feel confident in continuing to prescribe this medication to our own pets, as well as our patients, however, we support your decision as an educated pet owner to make the choice for the appropriate medication for your pet.  If you choose not to offer your pet Trifexis, we will be happy to discuss alternative therapies, however, all available parasiticides on the market have the potential to cause adverse effects and we cannot guarantee that any product will be 100% safe for any pet.

We will continue to monitor the FDA and Elanco for new information regarding negative claims against this drug.  If at any time we feel there is scientific validity to these claims, if Elanco issues a voluntary recall, or if the FDA mandates a recall, we will be certain to let you know promptly.

If you have any additional questions or concerns, please direct your questions to me at

Thank you!

Jo Fleming RVT

Jo Fleming RVT, CVPM | Uncategorized

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