I've been disabled for 12 yrs w/Chronic Right lower quadrant pain from a surgery that caused nerve damage & debilitating pain when I walk (feels like my right ovary is being twisted). I also have Osteoarthritis (Spine & all joints), 2 ruptured discs in my neck & 3 bulging discs in my low back. I've been taking Opana ER 40 mg twice/day and Hydromorphone 32 mg twice/day. My concern is that Opana ER is no longer being made. What substitute do you recommend?