Can Methadone Be Used For Pain In Terminal Chronic Pancreatitis?

I have severe chronic pancreatitis and am terminal. main symptoms include pain,nausea,diahrhea,statorhea, .I am on pain management meds and currently taking immodium ad for the diahrea without sucahcess. also my Dr's are suggesting I add methadone to my pain meds and my hospice nurse strongly agrees. I never heard of methadone used for pain. and wondering what med I can take for the diahrea