The U.S. Food and Drug Administration has authorized two nitenpyram products to prevent and treat New World screwworm (NWS) infestations in dogs and cats, giving pet owners and veterinarians a new tool against the potentially serious parasite.

The FDA issued an Emergency Use Authorization Sept. 3 for Capstar (nitenpyram) tablets and revised the existing authorization for Nitenpyram Tablets, the generic version of Capstar. Both products are now authorized for dogs, puppies, cats and kittens that weigh at least 2 pounds and are at least 4 weeks old, a news release from the agency said.

Nitenpyram Tablets were initially authorized in June 2026 for treatment only.

“Although the FDA has authorized or conditionally approved multiple products for the treatment of New World screwworm in dogs and cats, none were for prevention — until today,” said Timothy Schell, Ph.D., director of the FDA’s Center for Veterinary Medicine, in the release. “The FDA is addressing a previously unmet need and giving pet owners and veterinarians important tools to protect dogs and cats from NWS infestations.”

New World screwworm, or NWS, causes myiasis, an infestation in which fly larvae feed on the tissue of living animals. Most dogs and cats in the United States currently face a low risk of exposure because confirmed cases are limited to a specific geographic region.

Pets that live in, travel to or return from areas where NWS has been identified by state or federal animal health officials should be closely monitored. The FDA also recommends monitoring pets traveling to or returning from certain countries south of the U.S. border.

Signs of infestation can include visible maggots or foul odors in wounds or body openings such as the eyes, ears, nose or mouth. Owners should seek immediate veterinary care for pets showing signs of infestation.

According to the release, current U.S. case information is available through the U.S. Department of Agriculture’s dashboard of Confirmed Detections of New World Screwworm.

The FDA said the totality of available scientific evidence indicates Capstar and Nitenpyram Tablets may be effective in preventing and treating NWS myiasis in certain dogs, puppies, cats and kittens when used as authorized. The agency determined that the products’ known and potential benefits outweigh their known and potential risks.

Both medications are available over the counter in 11.4 mg and 57 mg tablets. Dosage is based on a pet’s weight. Neither product should be given to pets weighing less than 2 pounds or younger than 4 weeks.

Pet owners should review the applicable product fact sheet for detailed instructions. Fact Sheets, Freedom of Information Summaries and Letters of Authorization for NWS products are available through the FDA’s Emergency Use Authorization of Animal Drugs for NWS resources.

The EUAs will remain in effect until they are revoked or until the HHS secretary terminates the declaration that the potential public health emergency presented by NWS justifies emergency authorization of animal drugs for NWS.

Capstar is sponsored by Sergeant’s Pet Care Products LLC of Omaha, Nebraska. Nitenpyram Tablets are sponsored by Felix Pharmaceuticals Pvt. Ltd., based in Ireland.