PS Read the thread below there is good information there aswell ,
you know I have views about this but I feel you should put this question onto the ADD and ADHD Doctor forum, look at the top of the forums ,on the right, there is a Dr Resnik who is very good at answering these kind of questions about meds, my laymans/ parent answer is to wean him off them and try the supplemnts that have been shown to work, however you need your Doctors advice getting him off them.