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Study Shows Methylphenidate Linked to Chromosomal Changes
A new study found that every one of a dozen children treated for attention
deficit/ hyperactivity disorder with methylphenidate experienced a threefold
increase in levels of chromosome abnormalities-occurrences associated with
increased risks of cancer and other adverse health effects.
Newswise - In a small but startling preliminary new study, Texas researchers
have found that after just three months, every one of a dozen children treated
for attention deficit/hyperactivity disorder (ADHD) with the drug
methylphenidate experienced a threefold increase in levels of chromosome
abnormalities-occurrences associated with increased risks of cancer and other
adverse health effects.
The researchers say that to their knowledge this is the first study addressing
the potential chromosome-breaking effects associated with treatment of children
with methylphenidate, the generic name for a group of drugs that includes
Ritalin, Concerta, Metadate CD and others.
Methylphenidate is the most widely prescribed of a class of amphetamine-like
drugs used to treat ADHD, with more than 10 million prescriptions written for it
in 1996 alone. Between 1991 and 1999, United States sales of methylphenidate
increased more than 500 percent.
Researchers at The University of Texas M.D. Anderson Cancer Center in Houston
and the University of Texas Medical Branch at Galveston (UTMB) reported their
detection of the chromosome abnormalities in the journal Cancer Letters.
Their peer-reviewed paper is to be published several months hence, but the
journal editors have made it available online in the journal's "articles in
press" section.
The authors said they undertook the study because, even though methylphenidate
has been approved for human use for more than 50 years, "there are surprisingly
few studies" in either animals or human beings "on the potential for serious
side effects," such as causing mutations and cancer. In 1996, a report
discussing several two-year-long animal studies showed that the highest levels
of methylphenidate tested caused liver tumors in male and female mice. However,
similar studies in rats showed no such tumors.
The new Texas study involved researchers drawing blood from children diagnosed
with ADHD before they began taking methylphenidate in order to get a baseline
level of chromosomal abnormalities. Three months after the children had begun
taking the drug, the researchers drew the children's blood and tested it a
second time. Chromosomes are the bodies within cells that carry the genes and
genetic information. All 12 of the children whose before-and-after blood cells
were studied were treated with normal therapeutic doses of methylphenidate.
Most of the abnormalities found in the studied blood cells consisted of
chromosome breaks "and a higher frequency of aberrations is reported to be
associated with an increased risk of cancer down the line," said lead author
Randa A. El-Zein, M.D., Ph.D., an assistant professor of epidemiology at M.D.
Anderson who performed the blood studies using several techniques.
"It was pretty surprising that all of the children taking methylphenidate showed
an increase in chromosome abnormalities in a relatively short period of time,"
El-Zein said.
UTMB Professor of Environmental Toxicology Marvin Legator, the study's principal
investigator and senior author, cautioned, "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 that this study holds up." Of the 53 known human
carcinogens, Legator said 48 could be detected using the chromosome analysis
methods employed in this study.
El-Zein stressed that much larger studies at several medical centers are needed
to confirm the results of this study and to answer other questions not addressed
by it. One of these issues is the question of what happens when patients stop
taking methylphenidate. "Do the levels of chromosome abnormalities go back to
normal?" El-Zein said. "We don't know."
The Cancer Letters article by Randa A. El-Zein, Sherif Z. Abdel-Rahman, Matthew
J. Hay, Mirtha S. Lopez, Melissa L. Bondy, Debra L. Morris and Marvin S. Legator
can be found on the Web by clicking the "Articles in Press" button on
ScienceDirect's Cancer Letters page (http://www.sciencedirect.com/science/journal/03043835).
PDF copies can be obtained by contacting the UTMB public affairs office at the
email addresses or phone numbers above.
http://www.newswise.com/articles/view/510069