Oxycodone is pretty strong and sometimes has unusual side effects similar to this - my wife for instance was taking oxy, and she went totally nuts after a short time, same with dilaudid - so much so that I had to ask her doctor to find something else for her. Methadone, although there is so much negative publicity, is an excellent pain reliever, and the only one she could take after demerol had become ineffective. She was allergic to morphine, fentanol, etc.
What is the age of this person? what heart medications is he taking? What is the dosage (amount/frequency) of the oxycodone? How long has this been happening as is it all the time or just sometimes?