Xanax is also used for panic disorders. It can stop your breathing. Its symptoms are sudden changes in behaviour. A common side effect feeling lightheaded or having a seizure.Taking Xanax with other drugs that make you sleepy. It is also used to treat panic disorders. Some withdrawal may last up to 12 months or longer. You also take antifungal medicine. If you take Xanax during pregnancy, your baby could be born with life-threatening withdrawal symptoms. You should not be able to breastfeed. Usual adult dose for anxiety: 0.25 to 0.5 mg.