Nesporine plus has pramoxine as a local an aesthetic. From what I can find, LD 50 for pramoxine in rabbits is 39 mg/kg, intravenously. That’s a massive dose, your bun can’t have come anywhere near that.
http://www.thegoodscentscompany.com/data/rw1666781.html

I can find lots of warnings saying not to use neosporin plus, but nothing about what will happen if you do. Seizures would be a possibility. I’d just stop the neosporin plus right away and keep an eye on the bun. Try to not subject him to stress (chasing and catching him etc, loud noises, outdoors time) for a couple of days. Not that we ever want to subject our buns to stress, of course, but if there’s a risk of seizures in any individual, human or animal, a calm environment is important. (But don’t isolate him completely from human companionship, buns don’t like being alone).

You can continue with plain neosporin/triple antibiotic for as long as he needs it of course, it’s just the pramoxine that poses a risk. Plain neosporin doesn’t have that.