What is a Green Xanax Bar? Xanax, also known as alprazolam, is a medication used to treat anxiety and panic disorders. It was first used in the 1970s and is currently one of the most commonly prescribed medications worldwide. A Green Xanax Bar is a 3mg dose of Xanax and has the inscription of “S 90 3”. it is a benzodiazepine which enhances the work of particular chemicals in the brain to calm the body. You can Buy Green Xanax Bar Online.