Hi DC, welcome. I can't speak to Neurontin affecting you, as I've literally just started taking it 2 days ago, and starting at only 300mgs/day.
But I've had to take several different opiate meds in the last 3 years, Percocet included, though now I'm on Methadone. In my experience (and this would be to the greatest effect now on the Meth, though I've dealt w/it on other opiates), I didn't have so much of a physical problem getting aroused, as I did of "finishing the act" itself, as I've talked about on this board before (if you can find it via Search, it ended up being a long thread - just look for threads I started). That I pretty much still have all of the sensation, and am able to stay aroused fully, but it usually takes
FOREVER to complete, to find my happy ending

I'm sure it's because the particular nerves involved are being very suppressed. On one hand it's good because it basically feels good the whole time, but as you can imagine it's an extremely tiring experience all together. As I've joked previously, the big plus is that you'd be a real hit with the ladies, because they always seem to want a man who can go all night

(though who wouldn't?..... well, I mean, not
ME.... I'd want a
WOMAN who could go all night of course... being a man, myself..... I, uh..... oh, you know what I mean!!

)
Anyway, sorry to off on a bit there. Bottom line, I'm sorry to say is, to my knowledge there's nothing you really can do. It just comes w/the territory. Some people don't even feel their libido cooking, much less actually physically being able to get it up. I don't know, unless I'm missing something (wouldn't be surprised

then hopefully someone else will be along with some info. Good luck