Nexgard Spectra – contains afoxolaner and milbemycin oxime. Prevents heartworms, roundworms, whipworms, hookworms, lungworms, and flea and tick infestation. WOW! Life is so easy now! One chewable “treat” can kill any parasite to which your dog might be exposed.

According to the product information, “the most common side effects (affecting in between 1 to 10 animals in 1,000 animals) were vomiting, diarrhea, lack of energy, decreased appetite, and itching, which generally were short-lived and resolved spontaneously. Because fleas and ticks must start feeding on the dog in order to be killed by the medicine, the risk of transmission of diseases from an infected tick to a dog cannot be excluded.” In other words, the fleas and ticks have to bite the dog in order to ingest the chemical that kills them. The product DOES NOT repel fleas and ticks. If your dog does not have any fleas and ticks and you do not live in an area with high flea and tick populations, this products IS NOT necessary for your dog.

The label states “In the case of accidental ingestion, particularly in the case of children, medical advice should be sought immediately and the package leaflet or label shown to the doctor. People handling the medicine should wash their hands after handling the product.” In other words, the product is toxic, but they feel it is fine to feed it to our dogs. Once the product is ingested, there is NO ANTIDOTE if the pet has a reaction. The chemicals will remain inside the dog for a minimum of thirty days, probably more. The drug companies only tested efficacy of the drug out to 35 days. They did not conduct long term studies to see how much drug remained in the system for 60, 90, 120 days, or more. They only cared about the ability of the drug to kill fleas and ticks. Since effectiveness against parasites dropped at day 30, they determined a dosing schedule of 30 days, with no regard as to how long the product is detectable in the body. If your pet reacts poorly to the chemicals, it is unknown how long it will take to clear from the body. Note that the linked studies were funded by the drug manufacturer. Any conflict of interest?

We have already seen increased risk with combination products such as Trifexis, which combines milbemycin with spinosad. Spinosad falls into the same general chemical category as afoxolaner. Afoxolaner has been shown to have more side effects than spinosad since its release on the market. Combining afoxolaner with milbemycin may very well prove to be even more problematic. The product was tested on a very limited number of dogs before release onto the market. It seems to me the drug companies are getting these drugs to market extremely quickly, with less testing than ever.

Dogs with MDR1 mutations may be more sensitive to this combination than other dogs. Be very careful if you have a dog with this mutation. Consider using safer products for those pets. Unfortunately, once these drugs go to market, our pets are the test subjects. Statistically, only about ten percent of adverse event reactions are reported to the drug companies or oversight agencies (EMU, FDA). According to Dr. Elizabeth Carney, for the time period 1/28/17 to 5/2/17, reports to the FDA: there were 725 reports regarding Nexgard (not Nexgard Spectra), including 720 for dog, 1 for cat, and 4 for human (accidental) exposure. The top 6 reported clinical signs are:

  1. Vomiting/Emesis/Haematemesis (217)
  2. Lethargy (132)
  3. Pruritus/itching (103)
  4. Diarrhea/Loose Stool/Bloody Diarrhea (88)
  5. Anorexia/Not eating/Inappetance (72)
  6. Seizure (41)

Deaths reported total 21 (death + death by euthanasia).

Afoxolaner should not be used in pets with a history of seizures or epilepsy and it may cause your dog to have seizures. Interestingly, the product insert for Nexgard states it should be used “with caution in dogs with a history of seizures”, yet there is nothing like that on the label for Nexgard Spectra.

Are you willing to let your dog be the guinea pig that tests this drug combination?

I am not willing to allow my dogs or my patients to be test animals for these drugs.