Small study links Ritalin, increased cancer risk

By Paul Wenske
Knight Ridder Newspapers
Published on: 03/17/05

KANSAS CITY, Mo. - Health experts say the first human study linking Ritalin - the most popular drug used to treat attention-deficit problems - to a higher risk of cancer is raising alarms.

But they caution that more and larger studies should be conducted before pediatricians and therapists curtail prescribing Ritalin for the millions of children and adults in the United States who have benefited from its use for more than 50 years.

In a study to be published in Cancer Letters, Texas researchers found that after only three months, every one of a dozen children treated with Ritalin had a three-fold increase in chromosome abnormalities associated with increased risks of cancer.

"This study doesn't mean that these kids are going to get cancer, but it does mean they are exposed to an additional risk factor, assuming this study holds up," said Marvin Legator, an environmental toxicologist and principal investigator on the study by researchers at the University of Texas Medical Branch at Galveston and M.D. Anderson Cancer Center in Houston.

Legator acknowledged this week that the study group is small. But he said it was the first such study involving results in humans.

"This should raise a red flag," Legator said. "There's no question we need a bigger study before we take any further major action."

The drug is now made by Novartis Pharmaceuticals Corp. In a statement, Novartis repeated the safety record of the drug, which it said has been used for years "with no clinical evidence of a link to the development of cancer in humans.

"Novartis continues to stand behind the safety and efficacy of Ritalin, which is an important treatment option for patients with ADHD," the statement said.

Ritalin is the most widely prescribed drug for treating attention deficit/hyperactivity disorder. Six million to 10 million Americans, many of them children, take it. The drug is a mild central nervous system stimulant that helps address the neurochemical problems that underlie ADHD.

But medical experts said that, until more is known, parents should not be overly frightened of giving the drug to their children.

"Cancer is something to be scared about but untreated ADHD is devastating, too," said Kathryn Ellerbeck, a developmental pediatrician at the University of Kansas Medical Center.

Ellerbeck said untreated ADHD can lead to other life-threatening problems, including increased risks of accidents, addictive use of alcohol and drugs, and depression.

"This is concerning," she said of the new study. "But this is a drug that has been used for many years. And it works."

Avner Stern, a Kansas City-area psychologist who treats many children with ADHD, said that despite the troubling study, he would tell parents "to continue using it (Ritalin). Absolutely. But there needs to be more research to look at this carefully."

Researchers said they undertook the study because even though methylphenidate - the generic name for a group of drugs that includes Ritalin, Concerta, Metadate-CD and others - has been approved for human use for years, there "are surprisingly few studies" on potential serious side effects.

In 1996, a national toxicology report discussed several, two-year animal studies that showed that high levels of methylphenidate caused liver tumors in male and female mice. However, similar studies in rats showed no such tumors.

The Food and Drug Administration concluded those studies were not enough to signal that children should be taken off the drug. The drug's then-maker, Ciba-Geigy, told physicians that the national studies at the time suggested Ritalin remained safe and effective.

Gregory Kearns, chief of the division of pediatric pharmacology and medical toxicology at Children's Mercy Hospital in Kansas City, agreed that by itself the Texas study is troubling but not conclusive - mainly because it's hard to apply the results broadly.

"Millions of children get this medication on a daily basis," Kearns said. "We can't necessarily extrapolate results from those 12 kids to all these other children who use the drug."

Kearns said more study is needed because of the difficulty linking chromosome abnormalities and a higher risk of disease. Chromosomes are the bodies within cells that carry genetic information.

"There are many other things that have the ability to alter DNA, just like the alterations in the study," he said. "But not everyone who has chromosome alterations gets cancer and that's because there are also genes that repair damage."

Sukumar Ethirajan, a Kansas City-area cancer specialist, noted that genetic markers alone don't guarantee someone will get cancer. Ethirajan said environment also plays a major part.

The Texas study is being released at a time of concern about other drugs used to treat ADHD.

Canada recently pulled Adderall XR, another top-selling ADHD drug, after its manufacturer provided information about 20 patient deaths. Strattera, the first nonstimulant ADHD medication, has been linked by the FDA to liver damage.

In the Texas study, researchers drew blood from children diagnosed with ADHD before they began taking Ritalin in order to get a baseline level of chromosomal abnormalities. Three months later, the researchers drew the children's blood and tested it again.

All 12 children showed chromosomal breaks that are associated with an increased risk of cancer.

Legator said the consistency of the findings, despite the small size of the sample, "was astonishing" to the researchers. Still, he said, "Nobody wants to panic people.

"But my own feeling is we have to immediately set up a much larger study to confirm this. Any chemical that causes this kind of chromosomal change is of concern."