bipolar and is on Oxycontin

My son bipolar and is on Oxycontin. I am so scared of what this is doing to him and those around him. He was on meds for bipolar and he was so different. His way of thinking and how he acted was wonderful. He is now not taking the meds but is still taking the Oxycontin. I think he snorts it. I am just beside myself and don't know what to do anymore. He is 38 years old with a 10 year old son, My Grandson. They have lived with my husband and I for 2 years. My grandson lives with us every other week. We did tell my son that he had a dead line and was to move out next April. But I just could not take his verbal abuse any longer, so I told him he needed to fine a place to live before April. Well he was gone the next day. My grandson was with his mother one night and with me the next night. My son is staying in a garage. The nasty text messages from him are tearing me apart. I could write a book about the pain he has put me though. I must add that what I have done for him was because of my grandson. He worships my son and I don't want him to hurt any more then he is after the divorce.

What I want to know is how being bipolar and taking Oxycontin can affect your health.  His father had a heart attack at 50 and this really scares me. I just heard that some guy upset him on the road and he pulled up to this person and walked up to their truck and kicked the door in. I really need help; I don't want to see him in Jail. Thanks