Why do you not have the Xanax any longer? I will assume you are under the care of a doctor for your methadone maitanance. I am very naive about methadone w/d and did not know that anxiety was a symptom of detox. Your doctor may have been very smart in stopping the Xanax when he did. It is used as a very short term med and it pretty much maxes out around four months. After that time, it looses it's efficacy in fighting anxiety. If one continues to take Xanax beyond that point, all you are doing is keeping the w/d symptoms of Xanax at bay. You need to speak with your doctor if you are still having anxiety problems and discuss going on a long term anti-anxiety med like Klonopin or diazepam, to name only two.
Congratulations for getting clean and I hope your doc helps you keep up the fight.
Peace
Greenlydia