"wonderful drug. i have been on it for over six months and it has remained consistent. i used to be on concerta, which was ok, but i felt as if it lost its potency. vyvanse allows me to focus and maintain concentration. it also gives me a boost of energy. at times when i have missed a dose and left the house for the day i have felt tired and disinterested in the activities i was involved in. i have no side effects from it but i rarely have side effects to any drug. i have read that you are not supposed to have vitamin c while on it because it can interfere with the drug&#039;s ability to metabolize in one&#039;s system. i avoid vitamin c during the day and take some at night. take it around 8 or 9 so you can sleep at night."