FDA Warning! Your Flea & Tick Medication Could Cause Neurological Problems

Okay, pet owners, it’s time to dig deep and pay attention. There’s a new FDA warning about flea and tick medication on the horizon. In a recent alert, the U.S. Food and Drug Administration (FDA) issued a warning about isoxazoline-class drugs — which are commonly used to treat animals for fleas and ticks. Some of the most popular brands that contain these dangerous compounds are Bravecto, Nexguard, Credelio, and Simparica.

Keep reading, and we will fill you in on the details.


“The FDA carefully reviewed studies and other data on Bravecto, Credelio, Nexguard and Simparica prior to approval, and these products continue to be safe and effective for the majority of animals,” wrote the FDA in a statement released September 20.

“The agency is asking manufacturers to make the changes to the product labeling in order to provide veterinarians and pet owners with the information they need to make treatment decisions for each pet on an individual basis.”


So, really what they are saying here is that you should check with your vet before you treat your pet. Additionally, don’t panic — the reason for the big announcement was merely to inform the public. You don’t have to stop medicating your pet.

Image CC BY-ND 2.0 from CATS Pamuk via Flickr

Animals that had problems after exposure to Isoxazoline experienced:

  • muscle spasms
  • ataxia (loss of control of body movements)
  • seizures

According to the FDA, “although most dogs and cats haven’t had neurologic adverse reactions, seizures may occur in animals without a prior history.”


Before you panic and throw everything away, let’s break this down a little bit.

Image CC BY 2.0 from Jelene Morris via Flickr

Here’s what they are really saying. There isn’t anything newly dangerous about these drugs. They sent out the alert because until now the information was not included in the box with the medicine. Now there will be a warning label.

Additionally, if your animal is already on this medication (like mine) and they show none of the symptoms we listed above — there’s no reason to stop.


If your pet experienced any of the effects we listed above, here’s what to do. Please report the problem to the manufacturer (they are required to report it to the FDA), or report it directly to the FDA yourself. Secondly, obtain a copy of the Safety Data Sheet (SDS) for more information.

Here’s a list of the manufacturer’s telephone numbers:

  • Merck Animal Health (Bravecto): 800-224-5318
  • Elanco Animal Health (Credelio): 888-545-5973
  • Merial (Nexguard): 888-637-4251
  • Zoetis (Simparica): 888-963-8471

Image CC BY-SA 2.0 from cuatrok77 via Flickr

Let’s really dig in abd figure out what this all means for you and your pet.


The truth is, none of the stuff on the market for fleas and ticks is totally safe for our animals. However, it’s unrealistic to think that we can stop using it — fleas and ticks are out of control right now. We have to treat them.

As I said, I give Nexguard to my dog, Sophie. She handles it fine, and I foresee no problems. She had instant reactions to the medication I gave her before we tried Nexguard. Of course, this is entirely up to you, the pet owner, it’s ultimately your decision. Now you have the information the FDA wanted you to know.

Have any questions? Let us know in the comments.

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