I have been taking vicoden for 3 yrs now. I go to a pain management center for my back, Any ways All of the sudden it stop showing up in my system. is there a reason for this, cause i don't understand? It just doesn't make any sense. i take it every day 4 times a day.So it doesn't make sense why it wouldn't be there. I take dilanti, lyrica flexril, and vicodin. does anyone have any idea?