I have been taking Lortab 10/500 for several years as I have a severe back problem of which the neurologists advised against surgury. My Dr. just switched me to Norco 10/325. Now I know that the two main differences is the amount of codiene and acetaminophen. Is there any other difference other than the lesser amount of acetaminophen in the Norco that would cause it not to work as effectively? I even added a tablet of acetaminophen to my dose and it didn't help.