Morphine
"I was prescribed 60 mg MSContin twice a day switching from the 50mcg/hr fentanyl patch because of side effects problems and the fact it only works for the first two days. I was diagnosed with fairly severe osteoarthritis and degenerative disk disease, last year at the age of 26.  After wearing the patch for a few months my natural pain tolerance nearly vanished.  Now taking this MS-Contin feels like taking aspirin or a small ER/CR hydrocodone dose.  "