Clonidine
"I've taken this medicine since January 2010.  It controls one part of my blood pressure but not the lower number.  When taken with Cozaar both are under control.  However, recently I have been having problems with dizziness and confusion.  One day I forgot to take my medicines, left my pill box at home and found I had NO confusion that day or dizziness.  My concern is that I am developing a tolerance to these medicines which has happened in the past for me.  It is good for controlling blood pressure but these new side effects are scarring me."