Some cats and dogs on Bravecto, Nexgard, Credelio and Simparica, which use isoxazoline, had muscle tremors, ataxia and seizures, the agency said.
"Although most dogs and cats haven't had neurologic adverse reactions, seizures may occur in animals without a prior history," officials said.
Manufacturers of isoxazoline class treatment products are required to include new label information highlighting the potential for neurological issues.
The treatments are safe and effective for the majority of pets, officials said.
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