Brenda I am stage 4 chondrosarcoma and was switched to a fentanyl patch 25mcg. I had constant nightmares because I could no longer access deep sleep. I started taking zolpidem to help me sleep and I do now get about 6 hours and virtually no nightmares. When dozing in the day I get a lot of hallucinations and wake frequently. Good luck . This started in my right knee and because of misdiagnosis I lost 3/4 quads my femur and knee in surgery. You have my sympathy and best wishes.