Route of Administration and Regulatory Oversight of Ectoparasiticides.

Ectoparasiticide selection in cattle and other ruminants requires consideration of parasite biology, drug pharmacokinetics, route of administration, animal and production factors, residues, resistance, environmental effects, and regulatory requirements. This article reviews topical, injectable, oral, and sustained-release delivery systems and discusses their advantages, limitations, and practical applications in food-animal production. Particular emphasis is placed on the regulatory distinctions between products regulated by the US Environmental Protection Agency and those regulated by the US Food and Drug Administration, including requirements regulating approved, conditionally approved, and emergency-use products and the limitations of extralabel drug use in ruminants.