Man.... The last pain med I was on before going to Sub this time around was Meth....and let me tell ya....NEVER AGAIN. I'll NEVER touch Meth again, no matter how bad the pain is.
I'd rather do without and hurt.
In the last few months I have gone from Meth to Sub - and from Oxycontin to Sub - and with the Meth it was awful....but with the Oxy, it was minimal. That only tells me ONE THING....the Meth is much more difficult to come off of....regardless.
Good luck to you my friend.... Take Brian's advice and do a SMART taper....it will surely make the transition much much easier.
Wishing you well.