devices that do not differ substantially in purpose, design, materials, energy sources, function, or any other feature related to safety and effectiveness. The agency must conclude that similar regulatory controls are sufficient to provide reasonable assurance of safety and effectiveness. If a new device is put into class I in accordance with an existing regulation, the general controls applicable to that generic type of device ensure its safety and effectiveness. If a device is put into class II, the general controls and the applicable special controls that have been developed ensure the product’s safety and effectiveness. More than 1,800 generic types of devices are the subjects of classification regulations.

Premarket Notification

In the early days, the initial 510(k) submissions were simple to review, Phillips said, because there were no substantial differences between new devices going to market and older devices that had been on the market. However, the challenges associated with substantial equivalence quickly emerged. There was an expectation at the time that the Bureau of Medical Devices would start to develop performance standards for class II medical devices, but FDA did not have the resources to do it. Differences between new devices and old devices rapidly became more pronounced, and there were changes that would affect the intended use of a device and technologic changes. Another factor that challenged the system was that any kind of substantial shift toward using the premarket approval (PMA) process more frequently would seriously drain FDA resources. The PMA process was so burdensome and demanding that there was pressure in the agency to bolster the concept of substantial equivalence, which would allow products to go to market quickly with appropriate safeguards. Substantial equivalence evolved to compensate for regulatory realities.

A device is “substantially equivalent” to a predicate device if it has either of the following two groups of characteristics.


  • has the same intended use as the predicate and

  • has the same technologic characteristics as the predicate.


  • has the same intended use as the predicate, and

  • has different technologic characteristics, and the information submitted to the agency does not raise new questions of safety and effectiveness, and

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