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Outpatient prescription drug-related injuries are common in older patients, but many can be prevented

Medicare patients treated in outpatient settings may suffer as many as 1.9 million drug-related injuries a year because of medical errors or adverse drug reactions not caused by errors, according to a recent study that was cosponsored by the Agency for Healthcare Research and Quality and the National Institute on Aging (AG15979). About 180,000 of these injuries are life-threatening or fatal, and more than half are preventable, according to the researchers. They based their estimates on a study of over 30,000 Medicare enrollees followed during 1999-2000.

The researchers identified 1,523 drug-related injuries or "adverse drug events." Nearly 38 percent of the adverse drug events were characterized as serious, life-threatening, or fatal. About 28 percent of all the drug injuries were considered preventable by a panel of physician reviewers, as were 42 percent of the serious, life-threatening or fatal injuries. Examples of more severe adverse drug events included falls with associated fractures, bleeds requiring transfusion, hypoglycemia, and deterioration of kidney function. Cardiovascular drugs, followed by diuretics, analgesics, hypoglycemic agents, and anticoagulants were the most common medication categories associated with preventable adverse drug events.

When the researchers analyzed why the preventable adverse drug events occurred, they found that 58 percent involved errors made in the prescribing of medications, such as ordering the wrong drug or dose, not educating the patient adequately about the medicine, or prescribing a medication for which there was a known interaction with another drug the patient was already taking. The investigators also found 61 percent of preventable adverse drug events involved mistakes made in monitoring medications, such as inadequate monitoring or a delayed response to symptoms of drug toxicity in the patient. However, the failure of patients to adhere to medication instructions contributed to over 20 percent of the preventable drug-related injuries.

The study was led by Jerry H. Gurwitz, M.D., executive director of the Meyers Primary Care Institute, a joint endeavor of the Fallon Foundation and the University of Massachusetts Medical School. According to Dr. Gurwitz, computerized prescribing of medications in the office setting may provide the potential to prevent the prescribing of drugs with known interactions, as well as an opportunity to warn the prescriber to intensify monitoring of the patient. Efforts to enhance patient knowledge about their medication regimens are also essential to reducing the risks of drug-related injuries.

Details are in "Incidence and preventability of adverse drug events among older persons in the ambulatory setting," by Dr. Gurwitz, Terry S. Field, D.Sc., Leslie R. Harrold, M.D., M.P.H., and others, in the March 5, 2003, Journal of the American Medical Association 289(9), pp. 1107-1116.

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