Medicare patients suffer nearly two million drug error injuries yearly

Medicare patients treated in the outpatient setting 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 medical researchers sponsored by the federal Agency for Healthcare Research and Quality (AHRQ) and the National Institute on Aging. About 180,000 of these injuries are life-threatening or fatal, and more than half are preventable, say the researchers, who based the estimates on a study of more than 30,000 Medicare enrollees followed during 1999-2000.

"This is one of the first systematic examinations of the scope and causes of drug-related injuries to older patients in outpatient care," said AHRQ's director, Carolyn M. Clancy, M.D. "The findings from this important study can help reduce their risks of drug-related injuries by providing information needed for the development and testing of prevention strategies using system-based approaches."

The researchers identified 1,523 drug-related injuries or "adverse drug events." Nearly 38% of the adverse drug events were characterized as serious, life-threatening, or fatal. About 28% of all the drug injuries were considered preventable by a panel of physician reviewers, as were 42% of the serious, life-threatening or fatal injuries. Examples of more severe adverse drug events included falls with associated fractures, bleeding 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% involved errors made when prescribing 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% of preventable adverse drug events involved mistakes made in monitoring medications, such as inadequate laboratory monitoring or a delayed response to symptoms of drug toxicity in the patient. The failure of patients to adhere to medication instructions contributed to only 20% 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, or to warn the prescriber to intensify monitoring of the patient. Efforts to enhance patients’ knowledge about their medication regimens are also essential to reducing the risks of drug-related injuries."

SOURCE:  "Incidence and Preventability of Adverse Drug Events among Older Persons in the Ambulatory Setting,"  Journal of the American Medical Association, March 5, 2003 .