The U.S. Food and Drug Administration issued an alert to pet owners and veterinarians Sept. 20, 2018, warning of the potential for neurologic adverse events in dogs and cats when treated with flea and tick medicine with isoxazoline.

After the products obtained 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, according to the news release. Another product in this class, Credelio, recently received FDA approval. 

The FDA is working with manufacturers of isoxazoline products to include new label information to highlight neurologic events.

The FDA monitors adverse drug event reports received from the public or veterinarians, other publicly available information and mandatory reports from the companies that own the right to market a drug. Drug sponsors must report serious, unexpected adverse events within 15 days of the event. In addition, they must submit any events that are non-serious, plus any laboratory studies, in vitro studies, and clinical trials that have not been previously submitted to the agency, on a bi-annual basis for the first two years following product approval and annually thereafter.