Overview: Ritalin® is a drug used to treat attention deficit-disorder (ADD) in children and adults. A central nervous system stimulant, Ritalin (or methylphenidate) is similar to both amphetamines and cocaine, although its effects are generally milder and less pleasurable. Still, the increasing prevalence of ADD has prompted concerns about the potential of the drug -- and others like it -- for overuse.

Appearance: Several companies produce methylphenidate, and tablets vary in appearance, depending on dosage and manufacturer.

Street Names: Vitamin R, Rit.

Actions: Although how, exactly, Ritalin relieves ADD symptoms remains unclear, researchers believe that the drug alters biochemical pathways involved in the screening of irrelevant stimuli by increasing the action of neurotransmitters known as catecholamines.

Effects: Ritalin's effects begin shortly after ingestion and last about three hours. At low doses, methylphenidate increases alertness and focus, while blocking hunger and fatigue. Objective effects include increases in heart rate, blood pressure, and body temperature.

Side Effects: May include insomnia, rapid or arrhythmic heart beat, dizziness, irritability, and headaches. More severe reactions include agitation, changes in appetite and sleep habits, weight loss, and facial tics. Overdose is possible.

Addiction Potential: While there is little evidence of physical addiction to (or abuse of) Ritalin when used under medical supervision, it can produce both tolerance and physical addiction when used recreationally.

Legal Status: Methylphenidate is a Schedule II controlled substance, and both production and distribution are tightly controlled.

Trends: The U.S. has the highest rate of both ADD diagnosis and methylphenidate use in the world, with an estimated 1.5 million U.S. children currently using the drug each school day, with millions more taking such other ADHD medications as Adderall-XR® and Concerta®.

Demographics: While use of Ritalin has declined in recent years, prescription patterns involving similar drugs have soared, primarily due to growing demand within the United States. In 2005, 1.9 million U.S. prescriptions were written for Ritalin, while prescriptions for Adderall-XR and Concerta totalled 8.7 million and 8.2 million, respectively. During that same year, use of methylphenidate and dextroamphetamine figured into 7,873 U.S. emergency-room visits.