Thank you so much for your message. I'm so sorry to hear about your situation, it sounds heartbreaking and very tough.
I know it is really dangerous for my Mom to drink while on Oxycontin.... she says she doesn't care and if we loved her, we would leave her alone to do what she wants, as she's had a tough and miserable life....!! We have told both my parents that she could overdose fatally but the situation continues. We did think of calling her doctor ourselves to see if he knew how much she drinks, but decided it was enabling behavior.
At the moment anyway communication channels are down. My parents have 'disowned' me because I told them she was alcoholic and addicted to the Oxycontin. I laid down some new boundaries which made them particularly angry (e.g. I would not see them alone, without the support of my husband). I am not sure where things will go from here. I think I just have to trust God to look after them, and pray a lot.