As a long term veteren of Xanax I felt that I needed to put my two cent in on this topic because of my personal diary with alprazolam. To some degree, I have to agree partially with TWG. Sometimes it really is "all in your head", however, sometimes there are flat out fakes. I have tried alprazolam from Thialand, S.Africa, Germany and about every manufacturer in the US. Here is my take on it all.
1) You must realize that alprazolam does create a tolerance. With that in mind, I have had higher tolerances at times and relatively lower than others. This fact in itself, depending on your tolerance at any given time can make you think one way about an order of alprazolam and not truly know its "test tube" strength.
2) I have found that overall, from my own personal experiences that across the board, that US manufactured alprazolam, whether its mylan or Phizer is equal in strenth. I think that some of the times when I taken a thialand "upjohn", some of the good in it was like TWG said,,,"it was all in my head".
3)US generics have to go through rigourous inspections and quality control test at the manufacturing plants and have to meet the standards set forth of the origanl patenet holder of Xanax first complied with.
4)Addressing where to get it... well this is only a personl opinion, and here's what I do now and with success and peace of mind. I stopped using any foreign op's since they are busting packages left and right (yes i know from personal experience) because of hiring all the new customs personell to inspect a way larger percentage of packs. The good old days of interpharm and their counterparts are basically over. Yes you can get lucky and still get one slipped across but at what cost of time, money and your name getting put on US customs database for trying to import a scheadule 4 controlled substance? With all that in mind, I started hunting for a good US OP that dealt alprazolam without having to send in a Best if kept off the board load of records. Well so far I can only say good things about XanaxUSA.com . I do not even buy the brand name(which they offer). I get the generic 2mg bars and they work excellent. They deliver on time and with alprazolam or any benzodiazapine, THATS WHAT COUNTS TO ME.
As far as their pricing goes, well, the gap has really closed in the last year and a half between US OP's alprazolam prices and that of overseas and in some cases the site i use is actually cheaper than the overseas op's.
Ok I will stop rambling. I just hope this post has helped someone out there read the opinons of a long term alprazolam user. Other than that take care and have a great evening.

Sincerly,
Mr. AutoCad aka cadman