"xanax xr is very similar to klonopin. it&#039;s slow to start up (around an hour) then it lasts a long time (8-12 hours). it has subtle effects and no big highs and lows in anxiety like regular xanax ir does. i highly recommend xanax xr for all-day (or  most of the day) relief from anxiety and panic attacks. you might want to have regular xanax or ativan around for panic attacks on a when required, or as needed, basis for panic attacks only."