I think that you doctor should have gradually weaned you off Ativan and slowly introduced Xanax into your system, so many doctors make this mistake, they just don’t know enough about the medication and how they work in our bodies. They are both benzodiazepine but process differently within the brain, also Xanax is stronger and longer in your system than Ativan. Were you having a problem with Ativan, was it wearing off too quickly? This problem could happen and the doctor either increases your dose or switches you to a longer acting benzo like Xanax or Valium, whatever the reason for the change in your medication it must be done slowly to adjust your body to the new medication. I hope that you feel better soon and if you still feel that you need a change please research the information available online, it’s very helpful in doing the transition safely without a lot of unnecessary side effects.