Xanax, in particular, is usually only available on prescription. It is used to treat panic attacks and anxiety disorders, but is often abused by youngsters who enjoy the calming and relaxing effects.
Ben: Had a mad one last night. Could do with some bars. You got any man?
Tyrese: All out dude – will ask my bro.
Ben: Cool man – need something to help me chill.
Tyrese: No sweat, let me call him. He’ll be able to sort you out.
Whilst the drug can come in pills of various shapes and sizes, the nickname 'bars' is used because of the long, thin tablets that are common.
Here's a little Xanax rhyme to help you remember: