1) get him medical help, fast2) it is massively addictive, dangerous and withdrawals can cause depression and other manic emotional ups and downs3) they need to be weaned slowly, ramped down off the drug, vs cold turkey.
he has to want help, and he has to get professional help. this is not something you or your son can do alone. Oxycontin is a serious addiction that should be treated by a trained drug specialist. good luck