FDA Authorizes Generic Ivermectin to Prevent Screwworm in Cattle
The US Food and Drug Administration announced the authorization on August 27, describing it as its 14th emergency-use authorization related to New World screwworm. Bimectin injection may be used to prevent screwworm-related myiasis in cattle under the specified conditions and is available without a prescription.
The authorization covers administration within one day after birth, at castration or when a wound appears. It does not permit use in lactating dairy cows or in calves intended for veal production. Producers are required to follow the product label and accompanying fact sheet.
The FDA said cattle must be observed for a 35-day withdrawal period before slaughter. The agency identified compliance with that interval, together with the restrictions on dairy cows and veal calves, as necessary to limit drug residues and maintain food safety.
According to the agency, its decision was based on the available scientific evidence. The FDA said it was reasonable to conclude that the injection could help prevent New World screwworm myiasis in certain cattle when used as authorized, and that the product’s known and potential benefits outweighed its known and potential risks.
Bimectin is a generic version of Ivomec, which received FDA authorization in February 2026 for the same preventive use in cattle. The agency had previously approved Bimectin injection for treating and controlling several cattle parasites. The new emergency authorization applies only to the injectable formulation and does not cover other Bimectin dosage forms.
Timothy Schell, director of the FDA’s Center for Veterinary Medicine, said the decision expanded generic options for dealing with New World screwworm. He said the availability of both generic and pioneer products would prevent producers from relying on one manufacturer or product to protect their herds.
Bimectin injection is sponsored by Bimeda Animal Health Ltd., an Ireland-based company. The authorization remains in effect until the FDA revokes it or the US health secretary ends the declaration that the potential public-health emergency caused by New World screwworm supports emergency authorization of animal drugs.
