My 16yo son has grown apart from a close friend he's had since Y7 due to the friend's growing drug use. My son has tried cannabis but didn't like the next day feeling, and he's allowed beer at home so he's no Puritan and I'm aware of that. At their recent leavers prom, I met friends mum who I've only met in passing until now and she was keen for us to get the boys together in summer and take them somewhere they can mountain bike, which is what they used to do, we swapped numbers. The day after prom she messaged me saying her son had got a lift home from the after prom party and was very clammy and hot, and she wondered what they'd been drinking. I found out from my son today that his friend had taken ketamine and cocaine.
The friend is a lovely polite kid, he's slept at mine many times but I noticed that he's looking very gaunt and pale (especially so given his mixed race), he's no longer the handsome chap he was and looks aged. My son and son's girlfriend and other friends have repeatedly tried to talk to him about his drug use but he won't listen.
The friend's father lives aboard and he's not particularly close to his stepdad. His mum has a 3yo so I suspect a bit pre-occupied and hasn't noticed the drug use or changed in appearance. The friend has a 20yo sister who I suspect is enabling the drug use to some extent.
I'm very worried about this boy's safety, what can I do?