By the way, neither
oxycodone 10/325 or morphine sulfate 15mg are extended relief or
ER medications.
OxyContin or MSContin are both 12 hour, extended relief formulations of oxycodone and ms, respectively.
Perhaps you mean that you're using 15mg MSContin twice a day, with the Percocet 10/325 as needed for breakthrough pain?
If you are unclear, read the labels. If you are still confused, ask your doctor.