Trifexis, a flea killer and heartworm preventive introduced in 2011, is being blamed for nearly 1,000 dog deaths, but both the manufacturer and the U.S. Food and Drug Administration cautioned that no evidence has been found tying the drug to the claims.
Atlanta television station WSB learned after filing a Freedom of Information Act request that the FDA had received 965 complaints of Trifexis-related dog deaths. Pet owners have debated the drug’s safety on multiple websites and even started a Facebook page called Does Trifexis Kill Dogs?
FDA, which approves and regulates human and animal drugs, acknowledged that dog owners and veterinarians have lodged formal complaints about Trifexis (spinosad and milbemycin oxime).
“FDA is aware of adverse event reports in connection with Trifexis and continues to closely monitor them,” the agency reported in a prepared statement. “It is very important to realize that reports of adverse events do not necessarily mean that the product caused the event. Other factors, such as existing disease, exposure to chemicals or contaminants, foods, or other medications may have triggered or contributed to the cause of the event.”
WSB-TV also reported in late July that 1,500 Trifexis complaints were related to ataxia, the loss of muscle control.
The drug’s manufacturer, Elanco Animal Health of Greenfield, Ind., in March 2012 added ataxia and seizures to the list of reported adverse reactions. The drug’s initial approval noted mild side effects such as vomiting, itching, lethargy and diarrhea.
Some 70 million doses of Trifexis have been distributed through 15,000 veterinary clinics, said Elanco spokeswoman Julie Lawless.
“We keep finding vets who say, ‘We don’t understand [the claims],’ and frankly we don’t either,” Lawless said. “Trifexis is safe. It’s been rigorously tested and approved, and it’s got FDA approval and European Medicines Agency approval.
“What we continue to say is there is no link established between Trifexis use and death,” she added. “Reports are not an indication of cause.”
Trifexis, a beef-flavored chewable tablet, is available in five dosages based on a dog’s weight. The drug is indicated to prevent and treat flea infestations, prevent heartworm disease, and treat and control adult hookworms, roundworms and whipworms.
Dog owners should raise any concerns about Trifexis with their veterinarian, FDA spokeswoman Megan Bensette said.
“We encourage pet owners who have had problems they believe are attributable to any FDA-regulated products to work with their veterinarians to file a report with the agency,” Bensette said.