How to take alprazolam for sleep

I have been taking xanax for sleep for over 3 years .05 mg it has stopped working. My psych sugggested Mirtazapine 2 hours before taking the xanax (7.5 of the Mirtazaplne) this does work but I am having depression which was not a problem before. My hopes with this was to reduce the amount of xanax I use any Ideas would be most appreciated.