Gene Mutation Raises Risk of Side Effects from Parasite Preventatives

Lisa Selvaggio
by Lisa Selvaggio

According to findings from a recent study, over half a million cats in the U.S. should not be given certain parasite preventatives because they are at risk of serious adverse reactions. Pet parents who plan to use or currently use these products on their cats should inform themselves so they can make the right decisions for their pets’ health.


The MDR1 Genetic Mutation and Parasite Preventatives

Researchers at Washington State University conducted a study that determined eprinomectin is an ingredient that can cause severe side effects in cats who have a genetic mutation known as MDR1. More specifically, it can cause a severe or fatal neurological reaction.

In cats with this genetic mutation, the drug is able to enter their brain, resulting in neurological toxicity. And, according to experts, reports of adverse reactions occur frequently even though the majority of cats do not have the MDR1 mutation. In fact, the team started their research in this area—which involved reviewing medical records of cats who got sick or died after being treated with eprinomectin—because of an increase in the number of reports of neurological reactions.  

Symptoms of adverse reactions to eprinomectin typically develop hours after a product is applied to the skin. They include:

  • Increased salivation
  • Dilated pupils
  • Loss of coordination
  • Partial paralysis
  • Inability to retract or use the tongue
  • Seizures
  • Tremors
  • Coma
  • Death

Pet Parents Should Check Product Labels for Eprinomectin

Eprinomectin is an active ingredient in parasite preventatives like Centragard and NexGard COMBO. Cats with the MDR1 mutation should not be given any products containing eprinomectin.

Dr. Katrina Mealey led this research and is hoping that the U.S. Food and Drug Administration (FDA) will put warning labels on products that contain this ingredient. In the meantime, pet parents should check the labels of any products formulated to eliminate parasites like ticks, fleas, and worms to see if they contain eprinomectin.

If you aren’t sure if this ingredient is safe for your cat, talk to your veterinarian. Genetic testing can tell you if your cat has the mutation, and that information can guide your vet in determining which medications and parasite preventatives are safe for your kitty. Or, if you don’t genetically test your cat, you can play it safe by simply avoiding parasite preventatives that contain eprinomectin.

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Lisa Selvaggio
Lisa Selvaggio

Lisa Selvaggio is a freelance writer and editor, and our resident cats-pert, with certifications in pet nutrition and pet first aid. She enjoys producing content that helps people understand animals better so they can give their pets a safe and happy home.

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