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New Study Unlocks Mysteries of Ritalin
Although doctors have been prescribing Ritalin for years to treat attention-deficit/hyperactivity disorder (ADHD) in children, it’s been unclear exactly how the stimulant helps young people with the disorder calm down and maintain focused attention. A study recently conducted by researchers at the Brookhaven National Laboratory in Upton and the State University of New York at Stony Brook, indicates that the medication appears to work by increasing levels of the brain chemical dopamine. The researchers think they also understand why the drug—unlike other dopamine-triggering medications—is not addictive when given to children.
Dopamine is a hormone that’s known to play a role in feelings of pleasure, and, according to the study’s leader, Dr. Nora D. Volkow, dopamine is also intimately involved with the motivational process. As Ritalin increases dopamine levels in the brain, it may be increasing interest in activities that ordinarily do not illicit the fullest attention of a child with ADHD. For example, after taking Ritalin, responding to a page of arithmetic problems might become more interesting for a child who normally seems disinterested in math.
While previous research had shown that Ritalin--also known by its generic name methylphenidate--increases dopamine levels, those studies involved drug levels substantially higher than what’s normally prescribed to children. In an effort to see whether the smaller doses that are typically prescribed to children have the same effect on dopamine levels, Volkow’s team conducted their study with 11 healthy men (with no history of drug or alcohol abuse and who were not taking any medications).
Brain scans were done on the men using positron emission topography; one scanning session was done after they had taken Ritalin, and another after they had taken a non-medication placebo. The study reports that approximately an hour after the men took Ritalin, dopamine levels in their brains increased significantly.
Volkow said that Ritalin appears to raise levels of the hormone by blocking the activity of dopamine transporters, which would otherwise remove dopamine once it’s been released. Two groups of researchers have previously shown that some people with ADHD have too many of these dopamine transporters. What this means, she explained, is that the transporters “clean up” dopamine in the brain too quickly, making it difficult for the individual to pay attention. By blocking these transporters, Volkow added, Ritalin appears to keep dopamine levels sufficiently high enough so that a child with ADHD is able to maintain interest in tasks at hand.
According to the New York researcher, the study’s findings may also help explain why Ritalin, when used as recommended, is not addictive. Volkow said that, although Ritalin does increase dopamine levels similarly to many addictive drugs, including cocaine, alcohol and amphetamines, the key difference may be the length of time the drugs take to reach the brain. She noted that a drug must reach the brain very quickly for it to become addictive. Since, on average, an oral dose of Ritalin requires about an hour to have an effect on the brain, she said that this prevents the drug from causing the addiction-prompting “high” produced by most other drugs that stimulate dopamine. Volkow said that the time lag explains why children who take appropriate doses of Ritalin (based on age, weight and metabolism) do not become addicted to the stimulant. However, she pointed out, Ritalin can become addictive when tablets are crushed and then either snorted or injected since that makes the drug reach the brain much more rapidly.
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