A study released by the Centers for Disease Control (CDC) finds that patients taking stimulants for attention deficit hyperactivity disorder (ADHD) are making frequent trips to the emergency room amid a growing debate over the drugs' labeling.

The study, published in The New England Journal of Medicine, studied emergency room data from the National Electronic Injury Surveillance System-Cooperative Adverse Drug Event Surveillance (NEISS-CADES) project and estimated that 3,075 people visited emergency rooms in 2004 for adverse events caused by ADHD drugs.

"We found that visits to an emergency department for adverse drug events due to stimulant medications are not uncommon," the study concludes, adding that "the NEISS-CADES project probably underestimates the number of adverse drug events that are rare, previously unreported or difficult to diagnose" in an emergency room.

This study comes at a time when the content of ADHD drug labels is being hotly debated. While the FDA already plans to require the labels to carry additional warnings on use in children with cardiac conditions and other factors, some are calling for a black box warning for the drugs.

Steven Nissen, interim chairman of the Cleveland Clinic's Department of Cardiovascular Medicine and a consultant to the Drug Safety and Risk Management Advisory Committee that reviewed ADHD drugs, urges that approach, writing in the same edition of NEJM that it is a "fundamental fact that increasing heart rate and blood pressure by the administration of powerful cardiac stimulants is inherently risky." Several closely related compounds, ephedra and phenylpropanolamine, are so dangerous the FDA has banned them altogether, he wrote.