I have a 13 year old son who has been on concerta for 2 months for ADHD (been on Ritalin for 5 years very sucessfully). The Concerta has been great for school and the lasting time is a real improvement over the SR's. He is a wrestler and I have noticed, though, that at the end of the day if he is wrestling really hard his hands turn completely white and cold and he tells us he feels a bit dizzy. I believe that this is the time in which the drug is wearing off, but the symptom of white hands seems scarey. The Dr. thinks it is related to low blood sugar or something called a vaso-veso (sp?) reaction. He also says that the "come down" period in the day is a total myth and that parents just imagin this. I told him that it is not a behavior change but rather something that I have physically observed in my son's body. The Dr. has finally agreed for us to see a cardiologist for an EKG, just to rule out any heart involement. Has anyone ever heard of anything like this related to Concerta or Ritalin?? Thanks!