We used to give it IV, but now it comes as a nasal spray. So it has gotten trivial to administer. If you need Narcan, you need it. If you don't, it doesn't hurt you.

But here's a bit of advice from my experience:

Once you administer the Narcan, step back. That way when the druggie wakes up abruptly (and they do!) and wants to smack someone in the face for ruining their high, you are out of reach. I have had several of these druggies lunge at me.

Our ambulance standing protocol for "Unconscious, unknown reason" was Narcan (in case narcotics are the cause) and D50W (in case insulin shock is the cause). Narcan is harmless. If the patient is in diabetic coma (as opposed to insulin shock) then D50W is technically the opposite of what you want, but their blood sugar is already so high that an amp of D50W isn't going to make any difference. Mind you, I was a paramedic 25 years ago, so protocols may have changed since then.