CHICAGO -- Largely because of doctors' errors, older non-hospitalized Americans suffer about a half-million preventable drug side effects each year, ranging from nausea to life-threatening kidney failure, a study suggests.
About 20 percent of the side effects are caused by patients' mistakes, said the researchers, who studied about 30,000 people on Medicare in New England. But most of the preventable drug reactions result from doctors' errors.
"It's obvious that it's a major issue, a major problem," said Dr. Jerry Gurwitz, the lead researcher and a professor at the University of Massachusetts Medical School.
The findings appear in Wednesday's Journal of the American Medical Association.
Previous studies have found similar results in hospitalized patients, but there is little data on non-hospitalized patients, the researchers said.
With nearly 40 million Americans on Medicare, the government's health program for people over 65, the results suggest that more than 1.9 million drug side effects - about one-fourth of them preventable - happen each year in non-hospitalized elderly people.
About 180,000 of the bad reactions are life-threatening or fatal, and more than 40 percent of these may be preventable, the researchers said.
Citing data showing that more than 90 percent of adults age 65 and older take at least one drug per week, and about 40 percent use five or more weekly, they said their figures probably underestimate the problem.
A JAMA editorial said the study helps "provide a clearer view of the illusion of medication safety."
"Medications still pose a significant risk to patients ... despite decades of research and advances in drug therapy," said editorial author Dr. David Classen of the University of Utah.
Better communication among doctors could help prevent some bad reactions, Gurwitz said.
Educating patients could also help, said co-author Dr. David Bates of Boston's Brigham and Women's Hospital.
"Making sure they understand what they are taking, why they are taking it, and when they should take it remains a key component in preventing adverse drug events in the outpatient setting," Bates said.
Non-preventable reactions included skin rashes in patients with a previously unknown penicillin allergy. Preventable ones included bleeding in patients on blood thinners, blamed on inadequate patient monitoring or interactions with other drugs.
Heart drugs, diuretics and pain relievers were among the most commonly implicated drugs.
Some of the problems resulted from drug interactions and occurred because patients had several prescriptions from more than one doctor. A computerized system of the sort used in some hospitals could alert doctors to outpatients who should avoid a certain drug, Gurwitz said.
Patients could also help by bringing all their prescriptions to all doctors' visits, he said.
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