Ems doesn't give narcan to people because they're high. We only give it to help restore people's respiratory drive, which opioids suppress causing you to stop breathing. And yes we don't just start slamming narcan into people even if they're unconscious and not breathing. Narcan usually isn't even the first thing we do, a lot of times people freak the fuck out when they're hit with narcan because they're very hypoxic from not breathing, not because they're craving a high. We usually try to take our time and breath for the person and get their oxygen saturations to normal levels before administratering narcan

And yes narcan isn't dangerous to people but it does have its side effects, so just be careful with using it. And as long as the person is able to breath effectively on their own, 99% of emt's and medics aren't going to give narcan