FDA Issues Warning About Popular Flea and Tick Medicines

The U.S. Food and Drug Administration has issued new warnings for veterinarians and pet owners about the possibility of neurological side effects from popular flea and tick medicines.


The U.S. FDA wants pet owners and veterinarians alike to know that there is a potential for negative side effects from popular flea and tick medicines in the isoxazoline drug class.


The brand names of specific drugs the FDA is alerting pet owners about are Bravecto, Nexgard and Simparica. Since those drugs gained FDA approvals, the organization has gathered data indicating that some animals who use the drugs have had muscle tremors, seizures and ataxia. Credelio is another drug of the isoxazoline class and recently received FDA approval as well.


Related: What You Need Know About Flea and Tick Medication


All the products are approved to treat and prevent flea infestations in animals and to control flea infestations.


As a result of the data gathered, the FDA is collaborating with the manufacturers of isoxazoline to create and include new label information that would allow pet owners and veterinarians to know about the possibility of the neurological side effects, as they’ve been observed on a consistent basis in all the isoxazoline class products.


Prior to approving Bravecto, Credelio, Nexgard and Simparica, the FDA reviewed studies and data on all products. The FDA maintains that for the majority of animals who use the products, they continue to be safe and effective, but they want the manufacturers to change product labeling to give pet owners and veterinarians all information to make the best decisions for their individual pets.


The FDA encourages vets and pet owners to discuss the specific medical histories of each pet before deciding whether a product from the isoxazoline drug class is the right choice for the pet.


The data has been gathered as the FDA evaluates after-approval reports of side-effects, as well as other peer-reviewed scientific articles and the reports of veterinarians once a product is approved. The FDA watches specifically for adverse event reports for newly approved products to ensure safety for animals in general.


Related: 8 DIY Natural Flea Remedies for Your Home


If your pet takes any of the above products and you believe may have had an adverse reaction, the FDA urges you to report this not only to the drug manufacturer (who is legally required to report that to the FDA) or to submit a report to the FDA directly. The manufacturer information for drug companies are as follows:


Merck Animal Health (Bravecto): 800-224-5318



Elanco Animal Health (Credelio): 888-545-5973



Merial (Nexgard): 888-637-4251



Zoetis (Simparica): 888-963-8471


To report suspected effects directly to the FDA, you can contact them at their site.

Lori Ennis
Lori Ennis

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