Generally, yes. The FDA can block anything for any reason, including usability or safety concerns. The easiest process to move thorough is the 510k, but you can

Generally, yes. The FDA can block anything for any reason, including usability or safety concerns. The easiest process to move thorough is the 510k, but you can only do that if there are consensus-based standards or existing devices you can use as a predicate. Otherwise your product could be held up by the FDA for years or decades, with no clear path to release. It seems like cloning the Epipen could be a simple process, but you still have to show substantial equivalence and do a bunch of validation to ensure the product is safe and effective. I'm not an expert in this, by any means. All my knowledge comes from working in an FDA-regulated industry.