I think the “es” is because it’s not exactly ketamine, but a very related compound, rather than having to do with the administration type. There is one esketamine clinic near where I live. It is administered there intranasally, then they watch you for a bit in case of side effects, then someone else has to take you home. No driving or walking yourself. You have to get it and use it at the specially licensed clinic. It isn’t available at the pharmacy.

Side note: I’ve tried dozens of different medications in all sorts of categories for severe depression with constant suicidal ideation. SSRIs, SNRIs, atypical antipsychotics, atypical antidepressants, etc. Even weeks of TMS. Nothing worked... except a random trial of Adderall. The suicidal thoughts lifted within an hour. It was amazing. It surely doesn’t fix everything, but it’s nice to not want to die 24/7.