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Researchers Urge Caution on Ritalin-Cancer Link Finding

Despite FDA concerns, Texas scientists say their study was only preliminary

FRIDAY, July 1, 2005 (HealthDay News) -- As the U.S. Food and Drug Administration moved to examine a potential link between Ritalin and cancer, the scientists who first unearthed the connection stressed Friday that the finding was preliminary and should not be cause for panic.

The concerns about the drug, a stimulant that has been used to treat attention-deficit hyperactivity disorder (ADHD) for decades, surfaced during a FDA pediatrics advisory committee meeting Thursday. The findings, by researchers from the M.D. Anderson Cancer Center at the University of Texas, showed damage to the chromosomes of 12 children who had taken Ritalin for three months.

The advisory committee had been called to discuss yet another health issue surrounding the class of ADHD medications known as methylphenidates, to which Ritalin belongs: Some psychiatric side effects have been reported among children using Concerta, Ritalin and other versions of these drugs.

But the Texas scientists said their Ritalin study was far too small to prompt the parents of ADHD patients to abandon the drug.

"We're not telling people to all go off their medication because you don't know what this means," said Melissa L. Bondy, co-author of the study, which first appeared in the Feb. 16 online issue Cancer Letters. "You can't base changing practice on 12 patients. Look how many millions of kids are on this. Do you want to tell all the mothers and fathers to take their kids off of the drugs?"

Bondy said she and her colleagues have submitted a grant proposal to the National Institutes of Health for a larger study looking at more patients and more ADHD drugs.

"We definitely need a larger study," said lead researcher Dr. Randa A. El-Zein. If approved, the study would not even be funded until March 2006.

The government interest is there, however.

Scientists from the FDA, the NIH and the Environmental Protection Agency traveled to Texas on May 23 to examine the study methods used by the researchers. "They thought, 'Yes, we do have a public concern,' and that a larger study should be performed," El-Zein said.

"We're hoping that they'll see this as a major public health issue, and as something that needs to be done," Bondy added.

Meanwhile, the question of labeling changes because of possible psychiatric effects of Ritalin and other methylphenidates have been put on hold after the advisory committee told FDA officials that it was hesitant to recommend such changes.

According to an FDA release, committee members suggested waiting until more safety data have been collected on two other types of drugs used to treat ADHD -- methamphetamines such as Adderall and the non-stimulant Strattera, something that won't happen before early 2006.

The FDA should "delay the labeling change until they have a good sense of class effect," Acting Committee Chairman Robert Nelson, of The Children's Hospital of Philadelphia, told FDA officials according to the release.

"We heard there is no terrible signal," Office of Pediatric Therapeutics Director Dianne Murphy sadded.

The FDA had been considering labeling changes to all methylphenidates with regard to psychiatric events and potential cardiovascular side effects. A review had found 36 psychiatric events for Concerta, compared to 16 for Ritalin and other methylphenidates. These side effects included hallucinations and suicide ideation. Concerta had 20 cardiovascular event reports, while the other methylphenidates had four such reports.

Despite the committee's advice, Murphy said the agency still may change labeling about psychiatric side effects to "try to make it clearer what the situation is with regard to certain adverse events."

The FDA's decision to take a closer look at the psychiatric side effects of medications for ADHD did not surprise some experts.

"These types of issues theoretically were possible with the medication because of the way it works. It's not surprising that they've had some reports that relate to psychiatric side effects... " said Dr. Lenard Adler, director of the Adult ADHD Program at New York University Medical Center.

The drugs have been around for 40 years, Adler added, and have a "wide margin of safety."

"Any medicine that has therapeutic effect can have some side effects," Adler continued. "This is appropriate scrutiny by the FDA, but the benefits are also very clear and clearly outweigh the risks."

Another expert believes labeling changes may not be the answer.

"Labeling is an oversimplification of the problem," said Dr. Eugenio M. Rothe, director of the child and adolescent psychiatry clinic at Jackson Memorial Hospital and an associate professor of psychiatry at the University of Miami School of Medicine. "It scares people, and it doesn't address the other problems that are affecting the outcome. The problem is much more complex than that, and has to do primarily with the stigma associated with mental health conditions."

This is just the latest chapter in the ongoing debate over the safety of ADHD medications.

In February, Health Canada ordered Adderall XR off the market, after reports of sudden cardiac death in 20 patients. The FDA, however, elected at the time only to require the company to update Adderall's label to warn that it should not be used in anyone with structural cardiac abnormalities.

Almost 2 million children in the United States have been diagnosed with ADHD, according to the National Institute of Mental Health.

More information

Visit the National Institute of Mental Health for more on ADHD.

SOURCES: Randa A. El-Zein, M.D., Ph.D., assistant professor, epidemiology, and Melissa L. Bondy, Ph.D., professor, of epidemiology, both of University of Texas M.D. Anderson Cancer Center, Houston; Lenard Adler, M.D., director, Adult ADHD Program, New York University Medical Center, and associate professor, psychiatry and neurology, New York University School of Medicine, New York City; Eugenio M. Rothe, M.D., director, child and adolescent psychiatry clinic, Jackson Memorial Hospital, and associate professor, psychiatry, University of Miami School of Medicine; June 30, 2005, news release, FDA Advisory Committee Web site
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