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Is Trifexis safe?

Trifexis (spinosad + milbemycin oxime) has been rigorously tested and approved as safe by the FDA and other regulatory authorities around the world. Currently, more than 15,000 veterinarians in the U.S. trust Trifexis to protect their canine patients and have prescribed more than 90 million doses since it became available in 2011.¹

“Many veterinarians around the country have such confidence in the safety and efficacy of Trifexis that they prescribe it for their own dogs.”Dr. Jeff Werber, Veterinarian

Pet safety is our top priority

Elanco takes the safety of our products very seriously, and the health of your pet is always our top priority. So when recent news stories explored some dog owners’ claims that Trifexis may have played a role in the death of their dogs, we promptly investigated. However, there has been no causal link established between Trifexis use and death.

In fact, we conduct continuous, ongoing monitoring on Trifexis to determine if there are any signals or trends in the data, or any increases in frequency of certain types of reports. We also report all potential adverse events to the FDA.

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Protecting your dog

Pets need protection from the very real threat of heartworm disease, which can kill dogs. According to the American Heartworm Society, it is estimated that 1 million dogs have this potentially fatal disease.² For your dog’s safety, we recommend talking to your veterinarian about the best way to protect your dog from heartworms and other parasites.

One option is Trifexis. In the United States alone, veterinarians have prescribed more than 90 million doses¹, giving them and Elanco, the maker of Trifexis, confidence in the safety and efficacy of the product. Today, Trifexis remains a safe and highly recommended choice of veterinarians to kill fleas and prevent infestations, prevent heartworm disease and treat and control adult hookworm*, roundworm and whipworm infections.

In order for your vet to prescribe Trifexis, it first had to be rigorously tested and proven safe when used according to label directions.

*Ancylostoma caninum


Adverse events are undesirable effects that occur while on therapy with a medication, medical device, pesticide, or vaccine or other biological product. They may, or may not, be caused by the product or device.

If you suspect an adverse event has occurred with an Elanco product, please call us at 1-888-545-5973.

Please inform us that you would like to report an adverse event or Adverse Drug Experience (ADE). The technical services team will ask a series of questions about the event, complete FDA 1932 form and forward the report to the FDA Center for Veterinary Medicine (CVM). The technical services team member you speak with may also contact the veterinarian who treated your pet to obtain more information.

For additional information about adverse drug experience reporting for animal drugs, contact the FDA at 1-888-332-8387 or online.

The identities of all persons and animals is held in strict confidence by the FDA and protected to the fullest extent of the law. The reporter’s identity may be shared with Elanco unless requested otherwise. However, the FDA will not disclose the reporter’s identity to a request from the public, pursuant to the Freedom of Information Act.

Important safety information

Serious adverse reactions have been reported following concomitant extra-label use of ivermectin with spinosad, one of the components of Trifexis chewable tablets.

Treatment with fewer than three monthly doses after the last exposure to mosquitoes may not provide complete heartworm prevention. Prior to administration of Trifexis, dogs should be tested for existing heartworm infection. Use with caution in breeding females. The safe use of Trifexis in breeding males has not been evaluated. Use with caution in dogs with pre-existing epilepsy.

The most common adverse reactions reported are vomiting, depression/lethargy, itching, decreased appetite, and diarrhea. To ensure heartworm prevention, observe your dog for one hour after administration. If vomiting occurs within an hour of administration, redose with another full dose. Puppies less than 14 weeks of age may experience a higher rate of vomiting. Like all medications, keep Trifexis out of reach of children.

View full product label (PDF) for complete safety information.

More information

If you would like more detailed information on the safety of Trifexis, please refer to these documents.

Trifexis Adverse Event Technical Bulletin
Independent Pathology Review
FDA Center for Veterinary Medicine


If you represent a media outlet and would like to contact Elanco, please call 1-877-352-6261 and ask to speak with media relations.

1. Elanco Animal Health. Data on File.
2. American Heartworm Society data;, retrieved March 6, 2015.