After a year or so of IV drug use with various medications, including dilaudid , oxycodone , oxymorphone , fentanyl , etc, my vein that I always use was fine, never had any problems with it. This past month I acquired 50 40mg opana [oxymorphone] and IV d several of them. After this, I noticed my vein had become hardened. It s not the usual scar tissue, the vein itself is hard and I can feel it, it s about an inch long following the vein through my arm. What could be the cause of this?