suicidal friend

hi my friend is suicidal or at least he threatens to kill himself and I just don’t want him to Do something he may regret or anything else and I really care about him because he’s a good friend but he’s also an active and addicted drug user his parents want to send him to rehab and I agree but I don’t know what else to do because he’s given up on help for himself I just want to see him get better he’s already seeing a therapist and it’s not working for him. advice?