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Mixup Beyond the Medication Label

Helen Pervanas, PharmD, RPh, and David VanValkenburgh | August 1, 2018
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The Case

An 80-year-old man was admitted to a hospital for recurrent hypoglycemia. He had been seen at another hospital 2 weeks earlier for a similar episode, with a glucose level of 26 mg/dL. He was treated and released without a diagnosis at that time. Despite extensive diagnostic workup during the current admission, physicians could not identify the cause of hypoglycemia. Once his glucose level normalized, he was discharged home.

Approximately 2 weeks after the second discharge, the patient experienced another severe hypoglycemic episode and was admitted to a different hospital. At this time, his glucose level was 36 mg/dL; concurrent insulin level was 36.7 mIU/L (normal fasting level

However, the consulting endocrinologist recommended the family bring in all of the patient's medication bottles. The family returned with 12 different medications, none of which were labeled as an oral hypoglycemic agent. The resident used the codes on each pill to identify them and discovered that one bottle labeled as "doxazosin (Cardura)" actually contained the sulfonylurea, glimepiride (Amaryl) 4 mg. The patient had no history of diabetes, which likely suggested a pharmacy filling error. He had no further hypoglycemic episodes once this error was identified and corrected.

The Commentary

Commentary by Helen Pervanas, PharmD, RPh, and David VanValkenburgh

Most patients fill their prescriptions at community pharmacies. When dispensing medications, best practices in the community pharmacy involve accurate data entry, drug utilization review, product verification, and patient counseling. Performing a visual inspection of the contents of the prescription vial prior to dispensing may also identify medication errors before they reach the patient and cause harm.

In this case, the wrong medication was dispensed, which resulted in multiple hypoglycemic episodes and hospitalizations. In the United States, medication errors resulting in patient harm are estimated at 1.5 million annually with costs of approximately $3.5 billion.(1) Medication dispensing errors in community pharmacy settings have been reported at a rate between 1.7%–24%.(2-4) Extrapolating that number to the approximate rate of 3.9 billion prescriptions filled annually translates to between 66 million and 936 million possible dispensing errors per year.(5) In categorizing the types of errors, most errors involve incorrect medications or incorrect dosing or strength of a medication.(6,7)

Special populations such as older adults are at greater risk of harm as a result of adverse drug events (ADEs), which lead to increased emergency department visits and hospitalizations (8), as in this case. High-risk medications prone to ADEs include antidiabetic medications such as sulfonylureas (including glimepiride) as they can cause hypoglycemia and result in falls and even deaths in elderly patients.(9) Medication review may help prevent these types of events, and they are crucial to perform in this special population due to typically increased number of medications.(10) Furthermore, it is important to analyze adverse effects and adverse events and ensure they have a reasonable explanation. This patient had no medical or medication-related reason for extreme hypoglycemia, which should have been a red flag that prompted his providers to perform an in-depth review after the first occurrence. After repeated events such as seen in this case, providers should always perform a visual inspection of patients' medications. This check revealed the only clue to the dispensing error committed by the community pharmacy.

There is a direct correlation between increased workload in community pharmacies and the number of medication errors.(10) Other risk factors include high prescription volume, inadequate staffing, and problematic technology.(6,7) With many community pharmacies now being part of major retail chains, there is a growing focus on greater production and efficiency, which may in turn hinder safe medication practices and increase the potential for medication errors.(11) Of course, such pharmacies may also have advantages of greater resources and scale that may allow them to implement proceses and technologies to improve safety. At this point, there is no research comparing the error rates in large chain versus smaller local pharmacies.

Whether in a large or small pharmacy, several technologies and strategies can mitigate the potential for medication errors in community pharmacy settings. Implementation of barcode scanning in the final verification process has been shown to reduce medication errors and is a safe alternative to a pharmacist's visual check.(12) Combining barcoding technology with correct tablet imaging can further reduce the potential for errors.(4,10,13) This process involves scanning the barcode on the patient label and then scanning the barcode of the product being dispensed to ensure correct product selection. Additionally, during the barcode scanning process, an image of the scanned product can be viewed to verify correct product selection. In one study, the probability of dispensing the wrong medication increased from 9.43 per 1 billion prescriptions to 4.2 per 100,000 prescriptions when these two processes were omitted.(10)

Other strategies to reduce medication errors include addressing workload stressors for pharmacists, separating sound-alike or look-alike medications, always providing patient counseling, and performing comprehensive medication reviews, particularly for higher risk patients (i.e., older adults and patients on multiple medications).(11,14,15) The importance of patient counseling and visual inspection of the contents at the point of sale should be emphasized, as these actions can identify errors before they reach the patient. Performing medication reviews with the patient allows the pharmacist to check for drug interactions, assess appropriate medication use, monitor efficacy and safety, promote adherence, evaluate adverse or unexpected adverse effects, and perform a visual inspection of the medication in the prescription vial. These activities may reveal medication-related concerns and prevent adverse events.

Take-Home Points

  • Conduct a second data verification including a visual inspection of the medication in the vial prior to dispensing.
  • Provide patient counseling including visual inspection of the contents of the vial with the patient.
  • Perform medication reviews for patients who are older adults, taking multiple medications, and/or experiencing unexplained adverse effects.
  • Combining barcode technology with correct tablet imaging can reduce risk of errors.

Helen Pervanas, PharmD, RPh
Associate Professor of Pharmacy Practice
MCPHS University
Manchester, NH

David VanValkenburgh
MCPHS University
Manchester, NH


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5. Washington, DC: The Henry J. Kaiser Family Foundation; May 2010. Prescription Drug Trends. [Available at]

6. James KL, Barlow D, McArtney R, Hiom S, Roberts D, Whittlesea C. Incidence, type and causes of dispensing errors: a review of the literature. Int J Pharm Pract. 2009;17:9-30. [go to PubMed]

7. Ashcroft DM, Quinlan P, Blenkinsopp A. Prospective study of the incidence, nature and causes of dispensing errors in community pharmacies. Pharmacoepidemiol Drug Safety. 2005;14:327-332. [go to PubMed]

8. National Action Plan for Adverse Drug Event Prevention. Washington, DC: Office of Disease Prevention and Health Promotion, United States Department of Health and Human Services; September 2014. [Available at]

9. ISMP List of High-Alert Medications in Community/Ambulatory Healthcare. Institute for Safe Medication Practices. 2011. [Available at]

10. Cohen MR, Smetzer JL, Westphal JE, Comden SC, Horn DM. Risk models to improve safety of dispensing high-alert medications in community pharmacies. J Am Pharm Assoc. 2012;52:584-602. [go to PubMed]

11. Hassell K, Seston EM, Schafheutle EI, Wagner A, Eden M. Workload in community pharmacies in the UK and its impact on patient safety and pharmacists' well-being: a review of the evidence. Health Soc Care Community. 2011;19:561-575. [go to PubMed]

12. Wang BN, Brummond P, Stevenson JG. Comparison of barcode scanning by pharmacy technicians and pharmacists' visual checks for final product verification. Am J Health Syst Pharm. 2016;73:69-75. [go to PubMed]

13. Szeinback S, Seoane-Vazquez E, Parekh A, Herderick M. Dispensing errors in community pharmacy: perceived influence of sociotechnical factors. Int J Qual Health Care. 2007;19:203-209. [go to PubMed]

14. Cheung K, Bouvy ML, De Smet PAGM. Medication errors: the importance of safe dispensing. Br J Clin Pharmcol. 2009;67:676-680. [go to PubMed]

15. Teichert M, Luijben SN, Wereldsma A, et al. Implementation of medication reviews in community pharmacies and their effect on potentially inappropriate drug use in elderly patients. Int J Clin Pharm. 2013;35:719-726. [go to PubMed]

This project was funded under contract number 75Q80119C00004 from the Agency for Healthcare Research and Quality (AHRQ), U.S. Department of Health and Human Services. The authors are solely responsible for this report’s contents, findings, and conclusions, which do not necessarily represent the views of AHRQ. Readers should not interpret any statement in this report as an official position of AHRQ or of the U.S. Department of Health and Human Services. None of the authors has any affiliation or financial involvement that conflicts with the material presented in this report. View AHRQ Disclaimers
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