I've been taking Xanax XR 1 mg for the last 6 months or so. I was paying $40 for a month's supply. Today when I went to pick up my prescription and it was only $15. I thought hmmm, they must have gave me the generic instant relase ones. But when I opened the bottled it said alprozalam ER (substituted for Xanax XR 1 mg) was listed below, made by Mylan. I was under the impression that Xanax XR was only brand name, did this just come out? How effective is it?