Doctors prescribe Xanax primarily to treat anxiety disorders. Xanax is prescribed in several different doses depending on the severity of symptoms. The doses typically prescribed range from .25 mg to .5 mg three times a day. By comparison, a prescription for Valium may specify 2 mg to 10 mg up to 4 times a day. The potent nature of Xanax coupled with a relatively short half life makes it one of the most abused prescription drugs on the market today. Once addicted, it can be difficult to go through detoxification on your own.