Hello and welcome as a new member to Healing Well. I have read this post and also your other posts.
The 2 drugs you mention here, Xanax for anxiety and Prilosec for GERD or acid indigestion are prescribed for specific reasons and Prilosec is now easily available over the counter.
Do I think you should be trying to work out half lifes of drugs etc..........no. Everyone metabolizes drugs at different rates as well as some are metabolized through the liver and others excreted in urine.
I would not want any of our members to even consider the possibility of manipulating thier drug dosing in this manner.
This is my 2 cents worth