FDA warns of possible flea/tick med side-effects

The US Food and Drug Administration (FDA) today issued an alert to pet owners and veterinarians about possible neurological effects from use of certain flea and tick treatment products.

According to a spokesperson for FDA, as of July 31, 2018, the Center for Veterinary Medicine has received approximately 5400 reports of ataxia (difficulty standing/walking), muscle tremor, and/or seizures, in dogs and cats that received an isoxazoline product, out of millions of animals that have received one or more doses since these products came on the market.

Products containing isoxazoline products include: Bravecto, Credelio, Nexgard and Simparica and may be available in either a topical or a chew format, depending on the product.

Some of the neurological symptoms were seen during pre-market studies of these products, and the labels for some of the products already note the potential for neurologic events. Following a scientific evaluation of both the pre-market and post-market reports, FDA has determined that a label change is warranted across the category of isoxazoline products.

FDA urges pet owners to be on the alert for any neurologic effects after administering one of these products to their dogs or cats, and to report any adverse effects to the manufacturer or directly to FDA.

To report suspected adverse drug events for these products and/or obtain a copy of the Safety Data Sheet (SDS) or for technical assistance, contact the appropriate manufacturers at the following phone numbers:

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

If you prefer to report directly to the FDA, or want additional information about adverse drug experience reporting for animal drugs, see How to Report Animal Drug Side Effects and Product Problems.



2 thoughts on “FDA warns of possible flea/tick med side-effects

  1. The FDA is complicit in the injury and death of thousands of dogs and cats. The system for “approval” of these “drugs” (“premarket clearance”) represents absolute regulatory failure. It is the private consumer who offers his dog or cat as “test” subject for these drugs, which is not conducted beforehand.


    1. The system is similar in principle to the human drug approval process in that there are safety tests required before a product is approved for marketing, and continued ‘post-market’ collection of adverse effect data. Of course, the human drug approval process is far more rigorous, requiring a much larger number of volunteer test subjects for the safety and effectiveness testing.


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