I was diagnosed with ADD a while ago. can someone tell me why would 20mg XR Adderall only work for a little bit but not long as I need. I told my doctor about it so he decided to increase my dose to 25mg XR to take one once daily. Does anyone know why this is and if there are other medications that are similar to adderall and If so do they work the same!? Any feedback will be very appreciated. Thanks