The development, approval, and surveillance of medical devices have some features in common with those for prescription drugs, as well as others that are even more challenging. Yet the regulatory traditions of the device world are strikingly different from those of drugs and often much more problematic. This is shown in the linked feature by Lenzer and Brownlee (doi:10.1136/bmj.c4753), which describes the history of a vagus nerve stimulator to treat epilepsy—a device with a worrying risk-benefit ratio⇓.1

It would be unthinkable for a drug company to go to the Food and Drug Administration (FDA) of the United States or the European Medicines Agency and say, in effect, “This new drug is much like an older product we sell, except that we have added a new amine group and modified one of the side chains. Apart from that it’s pretty close, so we won’t be doing any new clinical tests on it. When can we begin marketing?” But this is essentially what happens with many new medical devices when they are approved. Unlike drugs, a new device can be approved for use if it is “substantially equivalent” to an existing product.2 The industry argues that many of its products, such as defibrillators or pacemakers, represent incremental modifications of predecessors, so the efficacy and safety of the older products can be presumed to apply to the new version as well.2

The device industry has …