Nearly 1.4 million Americans sought treatment in hospital emergency rooms (ERs) for adverse drug events (ADEs) in 2004 and 2005. The nation's elderly face the greatest risk of health problems due to drug reactions.

The new findings were published recently in the Journal of the American Medical Association, which reported that 1 in every 6 drug-related ER visits resulted in hospitalization, transfer to another health care facility, or admission to the ER for observation.

The study's findings were culled from information on the National Electronic Injury Surveillance System-Cooperative Adverse Drug Events Surveillance database. They indicate that unintentional drug overdoses were responsible for one third of the ER visits and half of the ADE-related hospitalizations.

The majority of the drug-related ER admissions involved women, and elderly patients accounted for nearly half of the ADE-related hospitalizations. According to the researchers, the ADEs resulting in hospitalization most commonly involved anticoagulants, insulin, opioid-containing analgesics, oral hypoglycemic agents, and antineoplastic agents.