Xanax is a prescription benzodiazepine useful to treat symptoms of anxiety. Xanax comes in immediate delivery and extended delivery forms. The conventional immediate-release tablets are available in 0.25 mg, 0.5 mg, 1 mg, and 2 mg of alprazolam. Extended-release Xanax pills are available in 0.5 mg, 1 mg, 2 mg, and 3 mg strengths of alprazolam.