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Vol. LXI, No. 5
March 6, 2009
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Digest

  According to NIDA-funded research, methylphenidate (Ritalin), which is commonly prescribed to treat attention-deficit hyperactivity disorder, can cause physical changes in neurons in reward regions of mouse brains.  
  According to NIDA-funded research, methylphenidate (Ritalin), which is commonly prescribed to treat attention-deficit hyperactivity disorder, can cause physical changes in neurons in reward regions of mouse brains.  

NIDA Study Shows That Ritalin Causes Changes in Brain Reward Areas

Investigators funded by the National Institute on Drug Abuse have shown that the medication methylphenidate (Ritalin), which is commonly prescribed to treat attention-deficit hyperactivity disorder (ADHD), can cause physical changes in neurons in reward regions of mouse brains—in some cases, these effects overlapped with those of cocaine. Both methylphenidate and cocaine are in the class of drugs known as psychostimulants. While methylphenidate is widely prescribed, this study highlights the need for more research into its long-term effects on the brain. These research findings were published Feb. 3 in Proceedings of the National Academy of Sciences.

“Studies to date suggest that prescribed use of methylphenidate in patients with ADHD does not increase their risk for subsequent addiction. However non-medical use of methylphenidate and other stimulant medications can lead to addiction as well as a variety of other health consequences,” said NIDA director Dr. Nora Volkow. “This study highlights the fact that we know very little about how methylphenidate affects the structure of and communication between brain cells.”

Added lead author Dr. Yong Kim, “Methylphenidate, which is thought to be a fairly innocuous compound, can have structural and biochemical effects in some regions of the brain that can be even greater than those of cocaine. Further studies are needed to determine the behavioral implications of these changes and to understand the mechanisms by which these drugs affect synapse formation.”

Abnormal Cells Prefigure Leukemia Diagnosis

Researchers have shown that abnormal white blood cells can be present in patients’ blood more than 6 years before diagnosis of a chronic form of lymphocytic leukemia. This finding may lead to a better understanding of the cellular changes that characterize the earliest stages of the disease and how it progresses. The study, led by researchers at the National Cancer Institute and the Food and Drug Administration, was published in the Feb. 12 issue of the New England Journal of Medicine.

Chronic lymphocytic leukemia (CLL) is a blood cancer that usually progresses slowly over many years. In this disease, abnormal white blood cells called B-cells accumulate in the blood and the bone marrow. The lymph nodes, spleen and other organs may also be affected. Although CLL is the most common form of leukemia in adults in Western countries, little is known about what causes the disease or how it develops.

“Our findings indicate that [the abnormal cells are] present in virtually all of CLL patients prior to full-blown disease,” said Dr. Ola Landgren of NCI. “This important discovery provides novel insights into the natural history of CLL and will open new fields of investigation for understanding its causes.” The risk of developing CLL for individuals with [the abnormal cells] appears to be low—on average, it is estimated that each year, only about 1 percent of them will develop CLL, he noted.

Genes Yield Hints About Dosage of Clot Preventer

In a large-scale study and an upcoming clinical trial, NIH scientists address one of the trickiest issues in prescribing medicine—how to quickly optimize each patient’s dosage of the common blood-thinning drug warfarin. One of the most widely prescribed drugs in the world, warfarin is used to prevent blood clots that can lead to heart attacks, strokes or even death. The drug is challenging for doctors to prescribe because the ideal dosage for each person varies widely and is hard to predict, yet is crucial for the patient’s safety.

Using information from thousands of genetically and geographically diverse patients, an international team of researchers developed a way to use genetic information from patients that could help doctors better determine optimal warfarin doses. The results of the analysis are published in the Feb. 19 issue of the New England Journal of Medicine.

Each person responds differently to warfarin. One person may need 10 times more of the drug than another, so it’s challenging to figure out where to start. The study revealed that when genetic information was included, the predictions of ideal dosages were more accurate, especially for patients at the low or high ends of the dosing range.

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