I'm sorry this is so distressing, Sam. Charlie's been a good friend in the past. No addict starts out being an awful person - addiction is biochemical. It's possible for anyone to become addicted if the right neuro pathways are stimulated long enough, but some people have an inborn neurological vulnerability. It really does run in families. It's heartbreaking to watch someone struggle with and/or succumb to a destructive addiction. At the same time, things change when the addiction takes over. Obligations, relationships, everything else disappears off the radar.
I don't know Charlie's situation and of course can't comment on his therapy. From what you've said here, though, somewhere along the line a problem has arisen. It is possible to call a medical office and communicate concerns about a patient. The office can't give you any information, they can't even really tell you that patient is on their roster, but you can voice a concern and request that your name not be given if/when they see Charlie and bring up the topic. If the system is set up correctly it should be possible for them to see every purchase Charlie makes, every fill of his prescriptions.
A talk from his provider won't fix the problem, though. Even if they monitor his use more carefully, he'll buy it privately. The best help you can probably give Charlie is not to enable him. If you feel able to talk to him about your concerns, you can direct him toward local services. He won't take your advice until he's ready, but you can be a friend by nudging him toward help. Addiction is hard for everybody.
