No Chromosomal Damage Seen From ADHD Medications

Stimulants commonly used to treat attention-deficit/hyperactivity disorder (ADHD), specifically methylphenidate and amphetamine, do not cause chromosomal damages in circulating white blood cells, a study in the December 2008 Journal of the American Academy of Child and Adolescent Psychiatry finds.

A study published in the December 18, 2005, Cancer Letters presented evidence of an increased frequency of three types of chromosomal damage in peripheral lymphocytes in 12 children after they had taken methylphenidate for three months. These types of chromosomal damage indicate DNA damage and structural changes to chromosomes and are associated with an increased risk of cancer.

Since this alarming finding, several smaller human, in vitro, and animal studies were published that failed to replicate the stimulant-associated chromosomal damage seen in the original study.

The new study was conducted with a methodology similar to the original study, but expanded the number of subjects and included mixed amphetamine salts (MAS) in addition to methylphenidate. Sixty-three children aged 6 to 12 with a DSM-IV diagnosis of ADHD were randomly assigned to open-label treatment with either methylphenidate or MAS for three months. None of them had taken stimulants before.

The researchers found no significant increase from baseline to the end of the three-month treatment in any of the types of chromosomal damage reported in the previous study in either patients who took methylphenidate (n=25) or those who took MAS (n=22). In addition to these 47 subjects, 14 discontinued study participation prematurely for various reasons, and two were switched to different medications by their physicians and completed three months of treatment. No significant association between treatment and chromosomal damage was found in these individuals.

The researchers examined the participants' blood samples, taken before and after the three months of stimulant treatment, for any chromosomal damage in lymphocytes. The percentages of cells with the damage at both time points as well as between the methylphenidate and the MAS groups were compared. No significant difference was seen between the two groups.

The study was conducted at the Duke University Medical Center by Kristine Witt, M.S., and colleagues affiliated with the National Institute of Child Health and Human Development (NICHD) and the National Toxicology Program of the National Institute of Environmental Health Sciences (NIEHS). NICHD and NIEHS, both divisions of the National Institutes of Health, provided funding for the study.

“These results add to the accumulating evidence that therapeutic levels of methylphenidate do not induce cytogenetic damage in humans,... and amphetamine-based products do not pose a risk for cytogenetic damage in children,” the authors concluded.

An abstract of “Methylphenidate and Amphetamine Do Not Induce Cytogenetic Damage in Lymphocytes of Children With ADHD” is posted at<www.jaacap.com/pt/re/jaacap/abstract.00004583-200812000-00006.htm>.▪