The premarket approval process is based on a demonstration of safety and efficacy through "adequate and well controlled" clinical trials. A positive outcome of the PMA entails the approval of the new device.
Class III devices are those that support or sustain human life, are of substantial importance in preventing impairment of human health, or that present a potential, unreasonable risk of disease or injury, or are new and present problems or risks of unknown safety or efficacy.
To obtain approval, the manufacturer must submit adequate scientific evidence to ensure that the device is safe and effective for its intended uses.
Some medical devices are sufficiently well known and their safety and efficacy are sufficiently well characterized and established not to require any review by the agency. However, they are still subject to general rules requiring adequate labeling, manufacturing and investigation of adverse events.
By the end of 2008, the FDA's Center for Devices and Radiological Health had exempted about 800 devices. The vast majority are designated as Class I devices and a small number are Class II.
Unfortunately, some manufacturers have obtained FDA clearance without disclosing the actual use of the device. For example:
The " electrodermal skin testing " devices used to diagnose and / or treat the range of diseases have been phased out because their manufacturers have told the FDA that they are biofeedback devices that (simply) measure the electrical resistance of the skin.
The applications did not disclose that the devices are sold with software that contains diagnostic or therapeutic advice.
“Spinal decompression” devices have been eliminated for traction (stretching) which may relieve back pain but is not very effective for this purpose. However, many professionals claim that the devices can shrink herniated discs. This is not proven (and unlikely) and is not a legally admissible claim.
The " heat lamps " (infrared lamps) that were licensed for the temporary relief of muscle pain were later marketed with fanciful claims that cover the range of medical conditions, including diabetes treatment and cancer cure.
Devices marketed for these purposes require market approval, which manufacturers know they cannot get. FDA controllers are aware of illegal marketing and have issued some warning letters. However, the agency did not make a decisive effort to drive them off the market.