My 4 year old son started taking vyvanse 20mg about 6 months ago. After about two months his dose was increased to 30mg. Two months later we increased it again to 40mg. Now my son is acting manic. He is screaming for no reason, peeing in his pants, spinning in circles, chewing on his shirt. To me he is acting as if he has taken nothing at all. I don't get it. The previous increase saw a positive reaction. Now this. Help?

I am very curious as to why a 4 year old was prescribed this in the first place!!