FDA: Expands EUA for New World Screwworm Drugs, Adds Prevention

• The FDA issued a new Emergency Use Authorization (EUA) for Capstar and revised an existing EUA for Nitenpyram Tablets.
• Both drugs are now authorized for both the prevention and treatment of New World screwworm (NWS) infestations in dogs, puppies, cats, and kittens weighing at least two pounds and aged four weeks or older.
• This authorization addresses a previously unmet need for NWS prevention, as prior approvals were only for treatment.
• The FDA concluded that the drugs are reasonably believed to be effective and their benefits outweigh potential risks for this animal drug emergency use.
• These over-the-counter EUAs will remain in effect until revoked or the HHS Secretary terminates the NWS public health emergency declaration.

This latest FDA veterinary drug authorization provides pet owners and veterinarians with vital new resources to protect animals from these parasitic infestations.

The U.S. Food and Drug Administration (FDA) has significantly broadened the scope of available veterinary treatments by issuing a new Emergency Use Authorization (EUA) for Capstar (nitenpyram) tablets and revising an existing EUA for its generic equivalent, Nitenpyram Tablets. These authorizations now permit both medications for both the prevention and treatment of New World screwworm (NWS) infestations, also known as myiasis, in specific companion animals. The expanded utility applies to dogs, puppies, cats, and kittens that meet minimum weight and age criteria, specifically those weighing at least two pounds and aged four weeks or older.

This development marks a crucial advancement, particularly regarding preventative care. While Nitenpyram Tablets had previously received an initial authorization in June 2026, that approval was solely for treatment purposes. The inclusion of prevention capabilities addresses a long-standing gap in available veterinary tools. Dr. Timothy Schell, who serves as the director of the FDA’s Center for Veterinary Medicine, highlighted this by noting that despite other authorized or conditionally approved products for NWS treatment, none had previously offered a preventative option. This latest FDA veterinary drug authorization provides pet owners and veterinarians with vital new resources to protect animals from these parasitic infestations.

The FDA's decision to grant these Emergency Use Authorizations for Capstar and Nitenpyram Tablets was based on a comprehensive evaluation of available scientific evidence. The agency concluded that there is a reasonable belief in the effectiveness of both products for the prevention and treatment of NWS myiasis when used according to the authorized guidelines. Furthermore, the FDA determined that the known and potential benefits of these animal drug emergency use products outweigh their known and potential risks, a critical factor in issuing an EUA.

Both Capstar, sponsored by Sergeant’s Pet Care Products LLC of Omaha, Nebraska, and Nitenpyram Tablets, sponsored by Felix Pharmaceuticals Pvt. Ltd. based in Ireland, are available over-the-counter. They come in two tablet sizes, 11.4 mg and 57 mg, with dosage determined by the animal's weight. It is imperative that these medications are not administered to pets weighing less than two pounds or those younger than four weeks old. Pet owners are strongly advised to carefully review the specific fact sheet for the relevant product to ensure proper usage. All associated product Fact Sheets, FOI Summaries, and Letters of Authorization are publicly accessible on the FDA’s website.

These specific EUAs will remain in effect until either they are formally revoked by the FDA or the Secretary of the U.S. Department of Health and Human Services (HHS) terminates the declaration that the potential public health emergency posed by NWS justifies the emergency use authorization of animal drugs for this condition. This framework underscores the temporary and conditional nature of such authorizations, which are designed to address urgent public health needs.

While the new FDA EUA New World Screwworm drugs offer enhanced protection, the immediate risk of NWS exposure for most dogs and cats within the United States remains low. Confirmed cases of NWS infestations are currently confined to a limited geographic region. However, vigilance is crucial for certain animal populations. Dogs and cats residing in, traveling to, or returning from areas where NWS infestations have been officially identified by state or federal animal health officials, as well as specific countries south of the U.S. border, should be closely monitored. Owners should be alert for common signs of infestation, which include visible maggots or the presence of foul odors emanating from wounds or body openings such as the eyes, ears, nose, or mouth. Should any of these symptoms be observed, immediate veterinary care is essential for the affected animals. For the most current information regarding NWS cases within the U.S., the U.S. Department of Agriculture provides a dedicated dashboard detailing confirmed detections of New World Screwworm.

For legal counsel to animal drug manufacturers, this FDA Emergency Use Authorization (EUA) for Capstar and Nitenpyram Tablets sets a precedent for addressing unmet veterinary needs, particularly for prevention. It illustrates the FDA's criteria and process for issuing EUAs for animal drugs, including the conditions for their duration and potential revocation, which is crucial for compliance and future product development strategies.

Source: Original reporting via U.S. Food and Drug Administration