generic adderall vs brand? | ADHD Information

does anybody know if there are differences in how they work?  My prescription coverage is a pain in the you -know-what and I've just had my daughter's prescription for Adderall filled for the first time.   It didn't help that the doc went on vacation the morning after he wrote the script and that my insurance does not cover ADHD meds for kids over 12 without prior approval (impossible to get while doc is away).   So I paid out of pocket for the first month's worth but didn't realize I was getting generic until I got home.  Normally generic is not a big issue for me but this is new territory and if anybody has info about the difference between the two I would appreciate if you share :)