I know every kid is different, but I wanted to share this in case someone else is struggling - our daughter has had impulsive behaviors for a long time, and finally when she was about 6 she went on ritalin. This is a life saver. When she is on ritalin, there is focus, and she will generally listen. When it wears off, she runs and runs and runs, and impulsive behaviors start - like leaving the sink running to overflow (an experiment), drawing on walls (on meds she would never do this), and so on.
Anyway, she has been on the meds for 2 years now and we have increased it a couple times as it has less effect as she grows.
Something unexpected happened a few months ago - we had made some dosage changes, and we noticed she was having really bad behavior at school - things that we were amazed to hear about - hitting, destroying property and more. After trying different things with the school - reward systems and such - other meds for anxiety, depression, we finally discovered she might have been on too high of a dose of ritalin.
Per her psychiatrist, we lowered the dose. Granted, there are now more windows of the hyperactivity / impulsive behavior, but it seems to have at least reduced the angry type behavior at school. Plus she is eating better.
Hope that helps!