WASHINGTON Two U.S. health agencies will conduct the largest-ever study of potential heart risks from medicines used to treat attention deficit hyperactivity disorder (ADHD), officials said on Monday.
The U.S. Food and Drug Administration said it will collaborate with the Agency for Healthcare Research and Quality (AHRQ) to examine clinical data of about 500,000 children and adults who have taken ADHD drugs, which include Novartis AG's Ritalin and Shire Plc's Adderall.
The analysis, expected to take about two years, will include all drugs currently marketed for treating ADHD. Millions of people take the medicines.
Because the drugs can increase heart rate and blood pressure, there are concerns they may raise the risk of heart attacks, strokes or other cardiovascular problems.
"Case reports have described adverse cardiovascular events in adult and pediatric patients with certain underlying risk factors who receive drug treatment for ADHD, but it is unknown whether or not these events are causally related to treatment. The goal of this study is to develop better information on this question," said Dr. Gerald Dal Pan, director of the FDA's Office of Surveillance and Epidemiology, in a statement.
In recent years, the FDA has been criticized as being slow to respond to signs of serious side effects with prescription drugs after they reach the market, most notably Merck & Co Inc.'s withdrawn arthritis drug Vioxx.
Merck pulled Vioxx from the market in 2004 after research found it doubled heart attack and stroke risk.
In August 2006, the FDA asked ADHD drug manufacturers to add information about heart-related concerns to the prescribing instructions for the medicines. The agency also told the companies in February 2007 to develop patient-friendly guides that explain possible cardiovascular and psychiatric risks.
Shire said it supported the FDA and AHRQ study. Officials at other drug makers did not immediately respond to requests for comment.
About 3 percent to 5 percent of school-age children, and about 4 percent of adults, have ADHD, according to the National Institute of Mental Health.
The disorder can cause trouble with concentration as well as hyperactivity and impulsiveness. Patients may have trouble with school, work or personal relationships.
(Reporting by Lisa Richwine)