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Medication Errors: What Is Their Impact?

  • David W. Bates
    Correspondence
    Correspondence: Address to David W. Bates, MD, MSc, The Center for Patient Safety Research and Practice, Division of General Internal Medicine, Brigham and Women’s Hospital, 1620 Tremont Street, 3rd Fl, Boston, MA 02120.
    Affiliations
    Department of Medicine, Brigham and Women’s Hospital, Boston, MA
    Harvard Medical School, Boston, MA
    Department of Health Policy and Management, Harvard School of Public Health, Boston, MA
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  • Sarah P. Slight
    Affiliations
    Department of Medicine, Brigham and Women’s Hospital, Boston, MA
    Division of Pharmacy, School of Medicine, Pharmacy, and Health, Durham University, Durham, UK
    Search for articles by this author
      The loss of a loved one can be devastating. The knowledge that their death could have been prevented makes it harder still. Medication errors can result in severe patient injury or death, and they are preventable. Although most errors are minor, there is a huge spectrum—and some are fatal. On January 4, 2001, Englishman Wayne Jowett was injected with a dose of the cytotoxic drug vincristine intrathecally rather than intravenously, a mistake that should never occur.
      • Dyer C.
      Government to introduce safer administration of cancer drugs after fatal error.
      He experienced leg paralysis and respiratory failure, and he was transferred to an intensive care unit. After he failed to recover, his mechanical ventilator was switched off a month later. At the inquest into the 18-year-old’s death, the coroner was told that 14 other patients had died or been left paralyzed as a result of the same mistake in the previous 15 years in the United Kingdom alone.
      • Dyer C.
      Government to introduce safer administration of cancer drugs after fatal error.
      Had specific prevention strategies been in place, eg, bar coding or a forcing function that would not allow vincristine to be injected through an intrathecal catheter, this would likely not have occurred. Fortunately, most medication errors are not this catastrophic. But how big a problem are they, and how can they best be prevented?
      In this issue of Mayo Clinic Proceedings, 2 articles address this domain. Wittich et al
      • Wittich C.M.
      • Burkle C.M.
      • Lanier W.L.
      Medication errors: an overview for clinicians.
      discuss some of the questions that providers may have about medication errors, reviewing the evidence about them, and Mixon et al
      • Mixon A.S.
      • Myers A.P.
      • Leak C.L.
      • et al.
      Characteristics associated with postdischarge medication errors.
      present a study of the frequency of medication errors after hospital discharge, clearly a vulnerable time.
      As Wittich et al
      • Wittich C.M.
      • Burkle C.M.
      • Lanier W.L.
      Medication errors: an overview for clinicians.
      note, medication errors are common, and their type and frequency vary substantially by setting; they are much more frequent in intensive care units, for example, where patients receive an average of 25 medications per day,
      • Cullen D.J.
      • Sweitzer B.J.
      • Bates D.W.
      • Burdick E.
      • Edmondson A.
      • Leape L.L.
      Preventable adverse drug events in hospitalized patients: a comparative study of intensive care and general care units.
      and much less of a problem in areas such as obstetrics, where medications are generally avoided. When medication errors result in harm, this is called an adverse drug event (ADE), and ADEs associated with medication errors are preventable. Previous studies of hospitalized patients have reported medication error rates of 4.8% and 5.3%.
      • Jimenez Munioz A.B.
      • Muino Miguez A.
      • Rodriguez Perez M.P.
      • Escribano M.D.
      • Duran Garcia M.E.
      • Sanjurjo Saez M.
      Medication error prevalence.
      • Bates D.W.
      • Boyle D.L.
      • Vander Vliet M.B.
      • Schneider J.
      • Leape L.
      Relationship between medication errors and adverse drug events.
      These errors can occur at any stage of the medication use process, eg, ordering, dispensing, administering, and monitoring. Although most medication errors do not result in patient injury, those that do are more likely to occur at the prescribing (56%) and administering (34%) stages in the hospital setting and are more commonly intercepted at the former stage (48%) than at the latter (0%). With respect to administration errors, there is typically no one between the nurse (or other person administering the drug) and the patient to detect or predict the error.
      • Bates D.W.
      • Cullen D.J.
      • Laird N.
      • et al.
      ADE Prevention Study Group
      Incidence of adverse drug events and potential adverse drug events: implications for prevention.
      Although there are many more studies of hospitalized patients than of outpatients, it is clear that medication errors are a problem in both groups, and many more medications are consumed outside the hospital than in it. In one study, Gurwitz et al
      • Gurwitz J.H.
      • Field T.S.
      • Harrold L.R.
      • et al.
      Incidence and preventability of adverse drug events among older persons in the ambulatory setting.
      assessed the incidence and preventability of ADEs in older patients in the ambulatory care setting and found that most errors occurred at the prescribing (n=246; 58.4%) and monitoring (n=256; 60.8%) stages. Prescribing-stage errors included “wrong drug/wrong therapeutic choice” (n=114; 27.1%) and “wrong dose” (n=101; 24.0%), whereas the 2 most common errors that occurred at the monitoring stage were “failure to act on available information relating to laboratory results” (n=154; 36.6%) and “inadequate laboratory monitoring of drug therapies” (n=152; 36.1%). Many preventable ADEs were related to errors in patient adherence (n=89; 21.1%), including “continuing to take a medication despite recognized adverse effects or drug interactions known to the patient” and “taking another person’s medication.”
      In contrast to the hospital setting, responsibilities for medication administration and monitoring outside the hospital are usually extended to the patient or a family member so that there are many more degrees of freedom for introducing an error in this setting. Just after a hospital discharge is another very vulnerable time for introducing medication errors. In a study of medical patients discharged from the hospital, Forster et al
      • Forster A.J.
      • Murff H.J.
      • Peterson J.F.
      • Gandhi T.K.
      • Bates D.W.
      The incidence and severity of adverse events affecting patients after discharge from the hospital.
      found that 19% had ADEs in the immediate postdischarge period and that 6% experienced a serious ADE. The article by Mixon et al
      • Mixon A.S.
      • Myers A.P.
      • Leak C.L.
      • et al.
      Characteristics associated with postdischarge medication errors.
      published in this issue of Mayo Clinic Proceedings examines this area in more detail; ie, they assess the frequency of medication errors and the association of patient- and medication-related factors with postdischarge medication errors, with a particular focus on patient literacy and numeracy. This study was conducted in patients with cardiovascular disorders, and this group often has many medications changed during hospital admission, especially after an incident event. The authors compared the preadmission medication lists of patients recently hospitalized for cardiovascular disease with their discharge medication lists and classified discordant medication as either an error of omission (the patient was not taking a medication that was on the discharge list) or an error of commission (the patient was taking a medication that was not on the discharge list). More than half of the hospitalized patients studied had at least 1 unintentional discrepancy between the 2 lists, and there were more in patients with lower numeracy or health literacy. High levels of depression were also associated with high odds of errors of commission. Although this study did not assess clinical outcomes such as ADEs, other studies have found exposure of inpatients to antidepressant drugs (odds ratio [OR], 3.3) and cardiovascular drugs (OR, 2.4) to be independent correlates of preventable and severe ADEs, respectively.
      • Bates D.W.
      • Miller E.B.
      • Cullen D.J.
      • et al.
      ADE Prevention Study Group
      Patient risk factors for adverse drug events in hospitalized patients.
      In the ambulatory care setting, cardiovascular drugs were among the most frequently used prescription drug classes in the study population and the most frequently implicated agents in preventable ADEs (n=103; 24.5%). In contrast, antidepressant and sedative/hypnotic drugs, which were used by more than 10% of the study population, were implicated in far fewer of the preventable ADEs (n=15; 3.6% and n=6; 1.4%, respectively). Thus, the prevalence of use of these medicines in the source population may reflect the frequency of ADEs in most, but not all, cases.
      Perhaps the most interesting findings from the study by Mixon et al
      • Mixon A.S.
      • Myers A.P.
      • Leak C.L.
      • et al.
      Characteristics associated with postdischarge medication errors.
      were from the explorations of literacy and numeracy. Lower numeracy was not associated with misunderstandings regarding dose or frequency but was associated with having a discordant medication and a misunderstanding in indication. In general, health care systems could do better at understanding the health care literacy and numeracy of their patients and at implementing interventions tailored to the specific needs of their patients.
      Health care provider factors can also contribute to medication errors. We examined the underlying causes of prescribing and monitoring errors in primary care practices and found a variety of health care provider factors that may have contributed to these errors,
      • Slight S.P.
      • Howard R.
      • Ghaleb M.
      • Barber N.
      • Franklin B.D.
      • Avery A.J.
      The causes of prescribing errors in English general practices: a qualitative study.
      including prescribers’ therapeutic training, drug knowledge and experience, knowledge of the patient, and perception of risk. High workloads, time pressures, and interruptions in the day-to-day activities of physicians and nurses are also known patient safety concerns, particularly regarding medication administration errors. Westbrook et al
      • Westbrook J.I.
      • Woods A.
      • Rob M.I.
      • Dunsmuir W.T.
      • Day R.O.
      Association of interruptions with an increased risk and severity of medication administration errors.
      observed interruptions occurring in more than 50% of nurses’ medication administrations; each interruption was associated with a 12.1% increase in procedural failures and a 12.7% increase in clinical errors.
      With respect to prevention, the most effective strategies depend on the clinical setting. In hospitalized patients, implementation of computerized physician order entry (CPOE) linked with clinical decision support has been the single most effective error-prevention strategy by providing physicians with dosing suggestions, assisting them with calculations and monitoring, and checking for harmful drug-allergy, drug-drug, and drug-disease interactions.
      • Bates D.W.
      • Gawande A.A.
      Patient safety: improving safety with information technology.
      • Bates D.W.
      • Leape L.L.
      • Cullen D.J.
      • et al.
      Effect of computerized physician order entry and a team intervention on prevention of serious medication errors.
      • Slight S.P.
      • Seger D.L.
      • Nanji K.C.
      • et al.
      Are we heeding the warning signs? examining providers' overrides of computerized drug-drug interaction alerts in primary care.
      If appropriately implemented, CPOE systems can help improve the communication among health care professionals and patients. Shamliyan et al
      • Shamliyan T.A.
      • Duval S.
      • Du J.
      • Kane R.L.
      Just what the doctor ordered: review of the evidence of the impact of computerized physician order entry system on medication errors.
      found that the use of CPOE systems was associated with a 66% reduction in medication errors in adults (OR, 0.34), with a similar effect found in children. These CPOE systems also contributed to a statistically significant (P≤.05) reduction in the number of ADEs in 5 studies.
      • Wolfstadt J.I.
      • Gurwitz J.H.
      • Field T.S.
      • et al.
      The effect of computerized physician order entry with clinical decision support on the rates of adverse drug events: a systematic review.
      Bar coding also has a large effect on inpatient medication safety.
      • Poon E.G.
      • Keohane C.A.
      • Yoon C.S.
      • et al.
      Effect of bar-code technology on the safety of medication administration.
      In the ambulatory care setting, it is less clear which strategies will be most important for improving safety, although computerized prescribing will undoubtedly be one of them. It is clear, though, that the immediate postdischarge period is particularly hazardous for preventable patient harm. One simple approach is to have pharmacists call patients after hospital discharge, which has been reported to decrease ADE rates.
      • Schnipper J.L.
      • Kirwin J.L.
      • Cotugno M.C.
      • et al.
      Role of pharmacist counseling in preventing adverse drug events after hospitalization.
      Other tools to prevent postdischarge harm are still being developed and are not yet in routine use in most organizations. One example is the Partners PostDischarge Medication Reconciliation Tool,
      • Schnipper J.L.
      • Liang C.L.
      • Hamann C.
      • et al.
      Development of a tool within the electronic medical record to facilitate medication reconciliation after hospital discharge.
      which was designed to make it easier for primary care providers to compare and contrast preadmission and postdischarge medication regimens by displaying identical medications next to each other and highlighting any changes that were made. Primary care providers are presented with an active reminder for all discharged patients whose medications have not been reconciled in full. Approaches that are tailored to meet patients’ specific needs, including issues such as literacy, numeracy, and elevated risk of specific issues, are likely to be helpful in the future.
      Medications are beneficial in the aggregate, but they can also cause substantial harm. Many ADE-prevention strategies have already been developed, although these are more maturely applied in the inpatient setting than in outpatients. Providers need to understand how to leverage these prevention approaches to make the medication-related care they deliver safer in each setting, but this will achieve optimal benefit only if we take advantage of these lessons and avoid repeating the mistakes of the past, such as what happened to Wayne Jowett and those who preceded him.

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      Linked Article

      • Medication Errors: An Overview for Clinicians
        Mayo Clinic ProceedingsVol. 89Issue 8
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          Medication error is an important cause of patient morbidity and mortality, yet it can be a confusing and underappreciated concept. This article provides a review for practicing physicians that focuses on medication error (1) terminology and definitions, (2) incidence, (3) risk factors, (4) avoidance strategies, and (5) disclosure and legal consequences. A medication error is any error that occurs at any point in the medication use process. It has been estimated by the Institute of Medicine that medication errors cause 1 of 131 outpatient and 1 of 854 inpatient deaths.
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      • Characteristics Associated With Postdischarge Medication Errors
        Mayo Clinic ProceedingsVol. 89Issue 8
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          To examine the association of patient- and medication-related factors with postdischarge medication errors.
        • Full-Text
        • PDF