what is a Xanax bar Xanax bars are small pill-sized Xanax tablets that are also known as “zanies” and “planks”. Each Xanax bar contains 2 mg of Alprazolam, but when broken half, it becomes 1 mg each. Smaller doses of Xanax include 0.5 mg and 0.25 mg, which is the lowest dose. The medicine is available in a generic form with the name Alprazolam. Why do people take Xanax? Xanax is a class of benzodiazepine that is beneficial for the management of panic and anxiety disorders. It stimulates the central nervous system that promotes calmness and reduces anxiety.