Methylphenidate, sold under various trade names, Ritalin being one of the most commonly known, is a central nervous system (CNS) stimulant of the phenethylamine and piperidine classes that is used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. Methylphenidate has been studied and researched for over 50 years. Some experts find a very good efficacy and safety record for the treatment of ADHD. Recently, some research raises questions.] Abuse is common and some experts believe addiction is possible.