The FDA and European regulators have received tens of thousands of adverse event reports related to popular flea and tick medications containing isoxazoline compounds. These medications, sold under brand names such as Bravecto, NexGard, Simparica, and Credelio, have been linked to seizures, muscle tremors, and loss of coordination in some animals, even those with no prior history of neurological issues. The FDA has updated safety warnings for these medications due to the troubling pattern of neurological reactions observed post-market.

The reported adverse events have raised concerns among pet owners, with over 32,000 reportable events in dogs treated with isoxazoline medications reported in the US between 2013 and 2017. The FDA advises pet owners to consult with their veterinarian about their pet's medical history before choosing a flea and tick prevention product and to report any concerning symptoms immediately. Additionally, ongoing class action litigation in US courts alleges that manufacturers did not adequately disclose the neurological risks associated with these medications during the early years they were on the market.