The Food and Drug Administration (FDA) defines a medical device as anything intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease, or intended to affect the structure or function of the body, which does not achieve its primary intended purpose through chemical action. The FDA uses the term “device” to refer not only to a physical device but also to its intended use. Stents approved for use in bile ducts, for example, cannot be used in arteries unless they are specifically approved for the new indication. For regulators, it is sometimes difficult to draw the line between devices and drugs. Drug-eluting disks are classified as drugs because their primary function is to delivery drugs whereas drug-eluting stents are regulated as devices because their primary action is considered to be the mechanical opening of arteries. The FDA has the authority to regulated devices before they are marketed, and device manufacturers are required to prove that their devices are safe and effective.
Devices are classified by the FDA based on their nature and on the extent of control needed to ensure their safety and effectiveness. Class I devices are those that are judged to pose the least risk. Class II devices are those considered to pose intermediate risks, and class III devices, such as prosthetic heart valves, are devices designed to sustain or support human life. In addition to being held to performance standards and subject to post-market surveillance, class III devices require premarket approval (PMA) before they can be distributed. Class II devices can obtain regulatory approval more easily than class III devices via the 510(k) process, which requires a manufacturer to show that its device is substantially equivalent to a legally marketed device. Devices can also be approved via humanitarian device exemptions, which are part of an effort to address orphan diseases. This exemption is meant for devices designed to address diseases so rare that clinical trials would be infeasible.
Investigational device exemptions (IDE) also exist to encourage the development of new devices. This exemption is required to conduct a study testing a new device in human subjects. The FDA regulates manufacturers but not physicians. Physicians can use legally marketed devices for off-label indications without FDA approval, but FDA approval is needed if physicians are going to conduct a study of an off-label indication. Only studies deemed to pose significant risks by an institutional review board (IRB) need FDA approval. Risk is determined not just by the device but by all parts of the study. When developing new devices, researchers should contact the FDA early in the development process in order to determine the best regulatory path and to avoid unnecessary studies.
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