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FDA 501(k) – aka, Substantially Equivalent

FDA Pre-market approval

Products such as new drugs and complex medical devices must be proven safe and effective before companies can put them on the market.

The FDA uses a risk-based, tiered approach for regulating medical devices, classifying them as either Class I, II or III. The class a medical device is assigned determines the type of premarketing submission/application required for FDA clearance to market.

Moderate risk medical devices are typically cleared for marketing based on an FDA determination that they are substantially equivalent to an already legally marketed device of the same type.


The 510(k) – Substantially Equivalent

The 510(k) is the FDA’s premarket submission process. This is done to demonstrate that a device is at least as safe and effective to a legally marketed device that is not subject to a premarket application.

Basically, this means that the device is substantially equivalent to another device.

The 510(k) requires that device manufacturers compare their device to one or more similarly legally marketed devices then make and support their substantial equivalency claims.

How does the FDA define a legally marketed device?

Legally marketed devices are defined in the Code of Federal Regulations 21 CFR 807.91(a)(3) as:

  • A device that was legally marketed prior to May 28, 1976 for which a premarket application is not required, or
  • A device which has been reclassified from Class III to Class II or I, or
  • A device which has been found SE through the 510(k) process.

The legally marketed device to which equivalence is made is referred to as the “predicate” and must not be one that is in violation of the Act.

What does it mean to be substantially equivalent?

A device is deemed substantially equivalent if, in comparison to a predicate, it:

  • Has the same intended use as the predicate

And, either

  • Has the same technological characteristics as the predicate OR
  • Has the same intended use as the predicate and has technological characteristics and the information submitted to the FDA does not raise new questions of safety and effectiveness, and demonstrates that the device is at least as safe and effective as the legally marketed device.

Substantial equivalence is just that. It is not claiming that the new device is identical to the predicate device. It refers to things like the intended use, design, energy used or delivered, materials, chemical composition, manufacturing process, performance, safety, effectiveness, labeling, biocompatibility, standards, and other characteristics.


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Past results afford no guarantee of future results and each case is different and is judged on its own merits.