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Dynamic Chiropractic – April 21, 2003, Vol. 21, Issue 09

Doctor Errors Cause 500,000 Preventable Drug Reactions Annually: Study

By Editorial Staff
The number of elderly Americans who take prescription medications is staggering: According to a recent national survey, more than 90 percent of people age 65 or older take at least one prescription medication weekly, and more than 40 percent take five or more different medications each week.1

When dealing with these kinds of numbers, a certain percentage of drug errors are bound to occur.

However, the prospect of that many people taking that many drugs raises questions about overall safety and the doctor-patient relationship: Just how many drug errors do occur; who is responsible for them; and how many are preventable?

A study published in the March 5, 2003, issue of the Journal of the American Medical Association provides startling answers to those questions,2 suggesting that more than one-quarter of all drug errors experienced by elderly patients are preventable, and that most are caused by doctors' own mistakes. A team of clinical researchers evaluated the records of more than 27,000 patients seen in a large, multispecialty group practice in New England between July 1, 1999, and June 30, 2000. All of the patients were 65 years of age or older and enrolled in the "Medicare+ Choice" plan. Reports from health care providers; reviews of hospital discharge, emergency department and clinic notes; computer-generated signals; and examination of administrative reports were used to document the frequency and severity of drug-related incidents.

The primary outcome of the study was the incidence of an "adverse drug event," characterized as any injury resulting from the use of a drug. Adverse events could have resulted from medication errors, such as errors in prescribing or dispensing medication, or from adverse drug reactions in which no error occurred. Events were categorized as significant, serious, life-threatening or fatal, depending on the severity of a patient's reaction to the drug; and characterized as preventable (if due to an error and preventable by any means) or not preventable.


A total of 1,523 adverse drug events were identified, primarily through review of clinic and emergency department notes. More than 27 percent of the events (421) were deemed preventable. While patients were responsible for 21.1 percent of the preventable adverse events, the majority of errors were the result of a doctor's action (or inaction), and occurred when drugs were first prescribed to patients, or while a patient was being monitored. Two hundred forty-six errors were noted in the prescribing stage; 256 errors were recorded during the monitoring stage of care.

Among the most common preventable prescribing-stage errors were choosing the wrong drug or therapy (114 incidents) and dosage errors (101 incidents). Inadequate patient education was cited 75 times, and prescribing a drug for which there was a known, relevant interaction with another drug was noted 56 times. Monitoring-stage errors consisted of delayed responses or failure to respond to evidence of drug toxicity. Failure to act properly on available information was the most common monitoring stage error (154 instances), followed closely by inadequate monitoring (152 instances).

The researchers also utilized a statistic called "person years" to determine the likelihood that a patient would suffer an adverse drug reaction. The rate of adverse drug events was 50.1 per 1,000 person-years, with a rate of 13.8 preventable events per 1,000 person-years. In other words, for every one thousand patients seen over a one-year period, 50 were likely to suffer an adverse drug event, and nearly 14 of those events were preventable.

In terms of severity, 578 events (37.9%) were considered serious, life-threatening or fatal; of those, 42.2 percent (244) were deemed preventable. Overall, more severe adverse drug events were more than twice as likely to be considered preventable, compared to drug events judged only "significant." Sixteen events resulted in permanent disability or death; seven of those, including five deaths, fell into the preventable category.

Notably, three classes of drugs - cardiovascular medications; antibiotics/anti-infectives; and diuretics - were responsible for more than 50 percent of all adverse reactions experienced by the elderly patients. Among the preventable events, cardiovascular drugs, diuretics and nonopiod analgesics were responsible for 24.5 percent, 22.1 percent and 15.4 percent of adverse reactions, respectively.

Gastrointestinal conditions such as nausea, vomiting, diarrhea, constipation, and abdominal pain were the most common types of adverse drug events experienced, followed by events related to electrolytes or renal function. The effects lasted one or more days in 70.3 percent of incidents. More than 65 percent of the preventable events had a duration of one day or longer.

As if these findings aren't alarming enough, the researchers also calculated what would happen if similar drug errors occurred nationwide. Projecting these figures to the total number of Medicare enrollees in the U.S. (approximately 38 million people), the researchers estimated that "more than 1.9 million adverse drug events - more than a quarter of which are preventable - occur each year" in the elderly population, adding that based on their estimates, "there are in excess of 180,000 life-threatening or fatal adverse drug events per year, of which more than 50% may be preventable" and that "For a number of reasons, these estimates are likely to be conservative."

The study authors offer several suggestions to reduce the number and severity of adverse drug reactions, and improve the quality of care in the elderly population:

  • Computerized monitoring and reporting systems. "Automated monitoring of some type may be practical as electronic medical record systems are more widely adopted."
  • Enhanced communication between physicians and pharmacists. "New approaches to enhance collaborations between those who prescribe drugs and those who know the most about the specific drugs, that is, clinical pharmacists, should be pursued in the ambulatory setting."
  • Getting elderly patients more involved. "The increased involvement of older persons in their pharmaceutical care also has the potential to be particularly beneficial in reducing medication errors."
  • Putting health care information online and making it more easily understood. "World Wide Web-based information could supplement verbal information provided by physicians and pharmacists. Personalized Web pages could provide information regarding a specific medication regimen and enhance patient adherence."

"In summary, adverse drug events are common and often preventable among older persons in the outpatient setting," the researchers conclude. "Our study provides additional evidence of the need to develop and evaluate new strategies to reduce the risk of drug-related injury in the ambulatory geriatric patient population."


  1. Kaufman DW, Kelly JP, Rosenberg L, et al. Recent patterns of medication use in the ambulatory adult population of the United States: the Slone survey. JAMA 2002;287:337-344.
  2. Gurwitz JH, Field TS, Harrold LS, et al. Incidence and preventability of adverse drug events among older persons in the ambulatory setting. JAMA 2003;289(9): 1107-1116.

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