Methylphenidate, sold under the trade names Ritalin among others, is a stimulant medication used to treat attention deficit hyperactivity disorder (ADHD) and narcolepsy. It is a first line medication for ADHD. It is taken by mouth or applied to the skin. Different formulations have different durations of effect.Common side effects include trouble sleeping, anxiety, and weight loss. More serious side effects may include psychosis, allergic reactions, prolonged erection, abuse, and heart problems. Methylphenidate is believed to work by improving the action of catecholamines in the brain. It achieves this by blocking dopamine and norepinephrine reuptake by neurons. Methylphenidate is a central nervous system (CNS) stimulant of the phenethylamine and piperidine classes.Methylphenidate was first made in 1944 and was approved for medical use in the United States in 1955. It was originally sold by CIBA, now Novartis Corporation. It is estimated that in 2013 2.4 billion doses of methylphenidate were taken worldwide. About 80% of this was taken by people in the United States making it the 47th most prescribed medication in that country. It is available as a generic medication. In the United States the wholesale cost of the immediate release formulation is less than US$0.30 per dose as of 2018.