Xanax is the shortest acting benzo around 4 hrs. Klonopin is the longest acting benzo and stays in your body for like 19 hrs. No one likes to use Ativan anymore. I've taken Ativan 1mg in the ER for acute anxiety many times and I took 6mg Ativan for my agitation but when I was inpatient at Johns Hopkins they didn't want me taking it due to addiction I guess so they stopped it. There really are no other choices. I told a lousy Dr in Baltimore that my anxiety and panic attacks were severe and she said "Have you made friends with your anxiety?" and couldn't believe it so I never went back to her!