76 Year Old Male Uses Prescribed Thru A Pain Clinic

76 year old male uses prescribed thru a pain clinic OxyContin . I'm the wife. I see personality changes-- very sensitive to what I Sao to him . Always stating I hurt his feelings. He just seems to be in a kind of stupor sometimes. Thought it might be us hearing but think it's that he is in a world of he own. He is able to maintain an outward appearance of being fine and takes care of business fine. I'm not sure how much pain he really has... He likes the feeling of the meds and is a 30 year plus recovering alcoholic. He also has developed an extreme like and excessive intake of sweet foods. He is not overweight. So what are the long term side effects of this med