What would give better pain relief, i am currently taking oxynorm immediate release 10mg and the doctors want to change it to oxycontin sr 10mg?

Depends on the dose.: Oxycodone is available in a long acting form called oxycontin. In that form the oxycodone is released over a period of time- between 8 and 12 hours- for most patients i see it is 8 hours. Oxycodone is also available in immediate release form which generally lasts for 4 hours. So an immediate release 15 mgm tablet every 4 hours would generally be equal to Oxycontin 30 mgm every 8 hours.