The safest way I know is to scribble over the marker several times with a DRY ERASE marker. Apparently, "permanent" markers and dry erase use the same solvent base, but the dry erase is, of course erasable! I've used this to get Sharpie off my monitor when Windex failed. (Don't ask why I wrote on my monitor with a Sharpie... :-/
Immediately after scribbling over the old marker, wipe away the dry erase with dry paper towels or scrap cloth. You may need to repeat this a few times. This will probably only work if the printing underneath has a slick finish. If the surface is porous and the pen has soaked through, I doubt anything else will get it off.
Good luck.