White Xanax Bar is a high-dose Xanax bar with 2mg of active Alprazolam. A rectangular cuboid imprinted on either side of the bar with "XANAX" or "2" distinguishes it from other medications. White Xanax bars are a highly effective treatment for anxiety, panic disorder, and phobia. Xanax (alprazolam) is a benzodiazepine that acts as a relaxant and is used to treat anxiety disorders, phobias, and panic attacks. White xanax Bars start their work within 30 to 60 minutes. The half-life of the drug is 11.6 hours.