My Mother Is 85 Has Old And Has Had 3

My mother is 85 has old and has had 3 brain surgeries and 5 days ago an extensive back surgery. This was all done in the past 8 months. Her surgeon increased her Xanax ( generic grade) from 1mg to 2mg. CVS said the script was on hold as Medicare said it was to early to fill. She was taking 1mg, 2 a night. The surgeon thought that taking 1 pill of 2mg would help her as she would not have to count or drop the 1mg pills. Why would they put this on hold? I take 2mg prescribed by my doctor and at times he may write 1mg if the 2mg is not available. The surgeon increased her Percocet from 5-325 to 7.5 325. There was no issue filling this. Since her brain surgery her memory has gone downhill. This is why she is with her 2 sons. Answer?