Xanax bars are the small rectangular tablet form of medication that treats generalized anxiety disorder and panic disorder in adults. Xanax bars contain alprazolam that works by attaching to a brain receptor called the GABA-A receptor. It helps the brain to calm by slowing down the activity in the brain. Doctors also tell people to buy Xanax bars online and use these bars for short-term relief from alcohol withdrawal, panic attacks with or without agoraphobia, help in insomnia, and prolonged seizures.