Nov 12 2013

Trifexis: Killing, Correlation, and Cost/Benefit

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?

Before you read on, I want everyone to know that I am not supported or compensated in any way to use, sell, or promote Trifexis.  I am also not pro-Trifexis, but rather I am trying to look at this situation as objectively as possible.  (Trifexis prevents heartworm disease, kills fleas, and kills intestinal parasites for one month for dogs)


I guess this all rides on correlation, which according to Meriam-Webster is “the relationship between things that happen or change together.”  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.


Now, lets just say that in a very small subset of animals, Trifexis causes them to die, develop cancer, or have a life-threatening illness.  If we discontinue Trifexis all together, then our animals are unprotected (possibly developing heartworm disease, flea infestation, and a host to intestinal parasites).  I have seen WAY more dogs die of heartworm infection than Trifexis (not to mention the problems that come with fleas and intestinal parasites).  In my opinion benefits far outweighs cost.

However, if you believe that a different prevention for heartworms and fleas is safer, then there are many products out there with good reputation.  Unfortunately there are cautions and concerns with these products as well (Heartguard and Collies, Proheart and Anaphylactic Reactions, Topical Flea/Tick Prevention) and nothing is without risks.

Life is inherently risky.  My goal as a veterinarian (and as a dog owner and father) is to minimize those risks for as many individuals as possible.  Trifexis has risks because life has risks.  We can reduce our risk for heartworm disease and make milti-level prevention as convenient as possible, but often other risks pop up during the process.


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.

– Doc Cleland

ePet Websites Admin | College Park Vet Blog

2 responses to “Trifexis: Killing, Correlation, and Cost/Benefit”

  1. Rebekah says:

    Thank you for writing this! Our doctor has written a similar letter, and we are now pointing people if the direction of this article also. We feel the same way and have been getting numerous calls and inquiries about this topic.

  2. dcleland says:

    Thanks! We try to recommend best medicine and appreciate those who do as well!


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