Drugs are defined in Section 201(g)(1) of the Federal Food, Drug, and Cosmetic (FDC) Act, as amended, mainly by the criterion that they are "articles recognized in the official United States Pharmacopeia, official Homeopathic Pharmacopeia of the United States, or official National Formulary, or any supplement to any of them [which are] intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in man or other animals." This definition is broad enough to encompass biologics for regulatory purposes; the statute also specifies that this definition "does not include devices or their components, parts, or accessories."
Biologics are defined under Section 351 of the Public Health Service Act as "any virus, therapeutic serum, toxin, antitoxin, vaccine, blood, blood component or derivative, allergenic product, or arsphenamine or its derivatives (or any other trivalent organic arsenic compound), applicable to the prevention, treatment, or cure of diseases or injuries of man." The meaning of these terms is elaborated in (21 CFR 600.3(h).
Devices are defined in Section 201(h) of the FDC Act as "an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including any component, part, or accessory, which is recognized in the official National Formulary, or the United States Pharmacopeia, or any supplement to them, intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, intended to affect the structure or any function of the body of man or other animals, and which does not achieve any of its principal intended purposes through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of any of its principal intended purposes." This definition also includes "devices intended for use in the diagnosis of conditions other than disease, such as pregnancy, and in vitro diagnostic products, including those previously regulated as drugs."