A new study has found that an all-day, extended-release stimulant for treating attention-deficit hyperactivity disorder (ADHD) remains effective for up to two years without significant side effects.
In the October issue of the Journal of the American Association of Child & Adolescent Psychiatry, a multi-institutional research team reports finding that treatment with Concerta, a once-daily form of the drug methylphenidate, successfully controlled ADHD symptoms in more than 200 children with ADHD. The study was supported by McNeil Pharmaceuticals, which manufactures Concerta.
"Although ADHD is recognized as a chronic disease, we've known very little about the effects of chronic treatment," says Timothy Wilens, MD, of the Massachusetts General Hospital (MGH) Pediatric Psychopharmacology Unit, lead author of the JAACAP report. "There have been concerns about whether the stimulant medications that are a mainstay of treatment continue to be effective, whether patients build up tolerance, or whether the drugs might have adverse effects on cardiovascular health or growth. This investigation sheds some important light on those questions."
The study initially enrolled more than 400 children, ages 6 to 13, who previously had participated in short-term, placebo-controlled trials of Concerta. In the new trial, all participants received the active medication at one of three dose levels. Dosage could be adjusted to improve effectiveness or reduce side effects. Participants' height and weight, blood pressure, heart rate and other clinical measures were taken at regular intervals during the study period. The children's parents and teachers were surveyed periodically regarding whether they believed treatment was effective in controlling ADHD symptoms
The entire, two-year study was completed by 229 participants, with others dropping out for a variety of reasons. Throughout the study period, measures of treatment effectiveness were consistent, with around 85 percent of parents and teachers reporting treatment results to be good or excellent. However, it was necessary to increase the children's dose by about 25 percent during the study, with most increases happening during the first year. All the children grew at rates considered normal for their age, and they gained only slightly less weight than would have been expected. In general, there were no clinically significant effects on blood pressure, heart rate, or other cardiac measures.
"We found these medications do continue to be effective in the long-term. While some particicipants did need to increase dosage beyond what could be attributed to their growth, any tolerance that developed seemed to be slight and limited to the first year," says Wilens. "We haven't seen any clinically meaningful problems with height and weight or any cardiovascular difficulties in this study, which also is the first to evaluate this kind of daylong treatment in a large group of children."
Wilens is an associate professor of Psychiatry at Harvard Medical School. The study's co-authors are Keith McBurnett, PhD, University of California at San Francisco; Mark Stein, PhD, University of Chicago; Marc Lerner, MD, University of California at Irvine; Thomas Spencer, MD, MGH; and Mark Wolraich, MD, University of Oklahoma.