Even so, the study authors and other specialists agreed that the 700,000 estimate was conservative because bad drug reactions are probably often misdiagnosed.
The study found that a small group of pharmaceutical warhorses were most commonly implicated, including insulin for diabetes; warfarin for clotting problems; and amoxicillin, a penicillin-like antibiotic used for all kinds of infections.
``These are old drugs which are known to be extremely effective. We could not and would not want to live without them," said Lambert, who was not involved in the research. ``But you've got to get the dose exactly right. Variations, especially on the high side, are really dangerous."
Those 65 and older faced more than double the risk of requiring emergency room treatment and were nearly seven times more likely to be admitted to the hospital than younger patients.
The results, from 2004 to 2005, represent the first two years of data from a national surveillance project on outpatient drug safety. The project was developed by the federal Centers for Disease Control and Prevention, the Food and Drug Administration, and the US Consumer Product Safety Commission. The study was published in today's Journal of the American Medical Association.
The database included 63 nationally representative hospitals that reported 21,298 bad drug reactions among US adults and children treated in emergency rooms during the two-year period. The tally is based on what emergency room doctors said were complications from using prescription drugs, over-the-counter medicines, dietary supplements, or herbal treatments.
The researchers said it translates to 701,547 complications nationwide each year.
``Experts had thought that severe outpatient drug events were common, but no one really had good numbers" until now, said lead author Dr. Daniel Budnitz, a CDC researcher.
