Ritalin; also known as methylphenidate is a stimulant for central nervous system. The main usage of Ritalin is in the treatment of Attention Deficit Disorder (ADD) and Attention Deficit Hyperactivity Disorder (ADHD). The medicine works by affecting chemicals in the brain and nerves that are responsible for the disorders. Ritalin is a prescription medicine and you can only order Ritalin online through online pharmacies.