Flea & Tick

FDA WARNS: Flea and Tick Medications Linked to Seizures, Muscle Tremors in Dogs & Cats

The U.S. Food and Drug Administration is warning pet owners and veterinarians of the risk of serious neurologic events including seizures, muscle tremors, and ataxia in dogs and cats treated with certain flea and tick medications.

flea and tick medications

Pet owners using flea and tick medications in the isoxazoline class – specifically Bravecto, Nexgard or Simparica and the newest FDA-approved flea/tick medication Credelio – are urged to closely monitor their pets for adverse neurologic events.

Since these products obtained their respective FDA approvals, data received by the agency as part of its routine post-marketing activities indicates that some animals receiving Bravecto, Nexgard or Simparica have experienced adverse events such as muscle tremors, ataxia, and seizures. Another product in this class, Credelio, recently received FDA approval. These products are approved for the treatment and prevention of flea infestations, and the treatment and control of tick infestations.

The FDA is working with manufacturers of isoxazoline products to include new label information to highlight neurologic events because these events were seen consistently across the isoxazoline class of products.

The FDA carefully reviewed studies and other data on Bravecto, Credelio, Nexgard and Simparica prior to approval, and these products continue to be safe and effective for the majority of animals. The agency is asking the 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. Veterinarians should use their specialized training to review their patients’ medical histories and determine, in consultation with pet owners, whether a product in the isoxazoline class is appropriate for the pet.

The FDA continues to monitor adverse drug event reports for these products and encourages pet owners and veterinarians to report adverse drug events. You can do this by reporting to the drugs’ manufacturers, who are required to report this information to the FDA, or by submitting a report directly to the 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

Pet owners and veterinarians who have additional questions can contact [email protected] or call 240-402-7002.



  1. Stasi

    Apr 17, 2019 at 7:46 am

    Every one of these drugs has been tested extensively and used for several years and shown to be safe. They are not sold over the counter. Every one of these drugs is sold as a prescription product so the person must go through a veterinarian and have their pet assessed in order for it to be given. I think this is a very inflammatory article and it’s very inaccurate how it portrays these particular drugs. It scares people when there is no need to be scared. That’s why you have to get them from a veterinarian. And yes I am a member of the veterinary community and yes we do prescribed these things. And no we have not had problems with reactions on any of these drugs. What we have had is animals that don’t come down with a lifelong case of Lyme disease or ehrlichiosis or anaplasmosis or flea allergy dermatitis.

  2. Miriam Nathan

    Sep 24, 2018 at 7:38 pm

    Warning on the package is not enough, few people read them and sales people are not interested in planting doubts in consumers’ minds. So, these drugs should be recalled !!!

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

To Top
Subscribe To Our Newsletter

Subscribe To Our Newsletter

Join our mailing list to receive the latest dog news, recall alerts, and giveaways!

You have Successfully Subscribed!