If these findings, which appear in the March 5 issue of the Journal of the American Medical Association, are extended to the total Medicare population of about 38 million people, that would mean more than 1.9 million adverse drug events are occurring each year, including 180,000 that are life-threatening or fatal.
"It's not surprising when you look at the amount of medications that are prescribed [to senior citizens]," says Zane Robinson Wolf, dean and professor of nursing at LaSalle University in Philadelphia.
A recent national survey found that more than 90 percent of people 65 years and older take at least one medication per week, more than 40 percent take five or more each week, and 12 percent take 10 or more. And this was among people who were not living in nursing homes or other institutions, who presumably would be taking even more.
Most of the studies looking at "adverse drug events" have focused on medication problems in general and within in-patient settings. The current study is one of a few that looks specifically at the elderly and, more specifically, at the elderly in an outpatient setting.
"The outpatient pharmacy and outpatient setting itself are as prone to errors as anywhere else," Wolf says.
This research team looked at 27,617 Medicare enrollees who received care at a group practice in a New England-based health maintenance organization over the course of one year. The researchers dug through hospital discharge summaries, emergency department notes, electronic clinic notes and reports from health-care professionals to find drug-related incidents.
An "adverse event" in this study referred to medication errors involving prescribing, dispensing, patient adherence or monitoring, or an adverse reaction not involving an error.
In all, the researchers pinpointed 1,523 adverse drug events, of which 27.6 percent were considered preventable. Of the total, 38 percent were categorized as serious, life-threatening or fatal. More of the severe events (42.2 percent) were considered preventable, compared with 18.7 percent of the least bothersome category, called "significant" adverse drug events.
The preventable errors occurred most often at the time of prescribing (58.4 percent) and monitoring (60.8 percent).
Medication categories most often associated with preventable mistakes included cardiovascular medications (24.5 percent), diuretics (22.1 percent), nonopioid analgesics (15.4 percent), hypoglycemics (10.9 percent) and anticoagulants (10.2 percent).
Errors with patient adherence, which is much less of a problem in hospital settings, here represented 21.1 percent of preventable errors.
"Health-care systems don't totally recognize how much responsibility there is for patients to take their medications correctly," says study author Dr. Jerry H. Gurwitz, executive director of Meyers Primary Care Institute and a professor of medicine at the University of Massachusetts Medical School. "The population is definitely more vulnerable and the intensity of medication use is so great compared to younger people. To be able to manage 10 medications would be overwhelming to any person."
Gurwitz found that patients sometimes took the wrong dose despite having been told what the right dose was, continued taking medication even though a health-care professional had told them to stop, took another person's medication, and continued taking medication when they knew there were side effects or interactions with other drugs they were taking.
How can the preventable errors be fixed?
Start with patient-doctor communication and patient education, Gurwitz says. "The most pragmatic things immediately are for patients and physicians to communicate with one another about medications that are being prescribed and used," he says. "Patients are often seeing multiple physicians and the physicians that they're seeing don't always know what medications the other is giving, so there's a real communication issue right there."
Dr. William Baird, an internist with the Ochsner Clinic Foundation in New Orleans, says he always has to keep in mind that his patients may have several other doctors in addition to him. "The cardiologist may have made a change or I may have made a change and the patient doesn't remember to tell us," he says.
Over the longer term, Gurwitz suggests that outpatient practices consider implementing computerized physician ordering systems similar to those found in hospitals.
"It would provide access to information about all medications the patient was taking and be able to warn a physician at the time the drug is prescribed about potential drug interactions," he says. "There's also the need for increased intensified monitoring of certain patients. A large proportion of errors that led to adverse drug events occurred at the prescribing and monitoring stages of drug therapy. That's where these systems are potentially most useful."
And it's a problem that is only likely to get worse in a system where, as Baird puts it, "it feels like it takes two to three drugs to treat any single problem."
A sore throat is no longer simply a sore throat, when you consider that prescribing antibiotics could interact with other pills the patient is taking. "We just keep adding more pills into the mix. It's a reasonable thing that we need to be very concerned about," Baird says. "Medicine has just become more and more complex, and with that complexity we have to come up with new means of 'first do no harm.'"