Medication Dispensing Errors and Potential Adverse Drug Events before and after Implementing Bar Code Technology in the Pharmacy

Context Bar code technology could help reduce medication dispensing errors in the pharmacy. Contribution The authors observed hospital pharmacy technicians as they dispensed medications before and after the installation of a storage and retrieval system that used bar code technology to label medications. After implementation of the bar codebased system, dispensing errors were much less frequent if the system required scanning of all dispensed doses. Some errors actually increased if the system did not require scanning every dose. Cautions Bar code technology was only one part of an entirely redesigned medication storage and dispensing system. Implications Properly implemented, medication storage and dispensing systems that use bar code technology may help to reduce medication dispensing errors. The Editors Medication errors in hospitals are common (1, 2), and dispensing errors made in the pharmacy contribute considerably to these errors (3). Overall, dispensing error rates are relatively low, but because of the high volume of medications dispensed, more than 100 undetected dispensing errors may occur in a busy hospital pharmacy every day (4). Because only about one third of these dispensing errors are intercepted by nurses before medication administration (3), many errors reach hospitalized patients (5). Therefore, dispensing errors are an important target for patient safety interventions. Bar code technology has been touted as a promising strategy to prevent medication errors (6, 7). In industries outside of health care, bar code technology has been widely adopted because of its ease of use and high degree of reliability. In the context of pharmacy dispensing, if all medications in the pharmacy had a bar code that is scanned to ensure that the correct medication in its correct dose and formulation is being dispensed, dispensing errors may be substantially reduced. On the basis of the theoretical benefits for patient safety, the U.S. Food and Drug Administration (FDA) has mandated bar codes for all medications used in hospitals by April 2006 (8), and many institutions are beginning to adopt this technology to increase the accuracy of the dispensing and administration processes. Despite enthusiasm for this technology, few published studies have evaluated the effect of bar code technology on dispensing errors (9, 10). Previous work has also demonstrated that the implementation of health information technology (HIT) may result in unintended consequences and new types of errors (1113). Therefore, the decision to adopt this technology must be informed by a careful evaluation of its efficacy and limitations. To that end, we evaluated a recent implementation of bar code technology in a large hospital pharmacy to measure the changes in the rates of dispensing errors (see Glossary) and potential adverse drug events (ADEs) (see Glossary). Methods Study Site and Study Period We performed a before-and-after evaluation study over a 20-month period in a 735-bed tertiary care academic medical center, where approximately 5.9 million doses of medications were dispensed per year from the central inpatient pharmacy. Between February and August 2003 (prebar code implementation period), we measured the baseline rates of dispensing errors and potential ADEs. In November and December 2003, the hospital pharmacy converted to a bar codeassisted dispensing process. After the conversion, we remeasured the rates of dispensing errors and potential ADEs between May and September 2004 (postbar code implementation period). Observations in both periods were conducted on weekdays during the day shift, when most medications are dispensed. Dispensing Processes during Pre and PostBar Code Implementation Periods The Figure depicts an overview of the medication use process during the 2 observation periods. In both observation periods, the dispensing process involves 3 major steps that are commonly used in approximately 76% of U.S. hospitals (14) (Table 1 and Figure). In the first step, medications delivered to the pharmacy are stocked in the pharmacy inventory. The second step, known as filling, requires a pharmacy technician to retrieve the appropriate medications from the pharmacy inventory. The third step, known as verification, requires a staff pharmacist to verify the accuracy of the medications filled by the technician before delivery to patient care areas. If the staff pharmacist detects a dispensing error, the medication is returned for refilling. While the stocking and filling steps changed extensively with bar code technology implementation, the pharmacist's visual inspection step remained functionally unchanged in the postbar code implementation period. In both periods, medications dispensed from the pharmacy would be delivered to either patient-specific medication drawers or semi-automated medication cabinets (Sure-Med, Omnicell, Mountain View, California) on the patient care units. Figure. Overview of the pharmacy dispensing process. *Sure-Med, Omnicell, Mountain View, California. CPOE = computerized physician order entry; MD = physician. Table 1. Description of the Dispensing Processes Studied in the PreBar Code and PostBar Code Implementation Periods In the prebar code implementation period, we studied 3 major dispensing processes: 1) Sure-Med fill, 2) first-dose fill, and 3) cart fill. Each medication dose (see Glossary) was dispensed by only 1 of these processes (Table 1). In the prebar code period, medications were stocked manually onto shelves and the filling step for all 3 processes was performed manually, with the pharmacy technician relying solely on visual inspection to pick the appropriate medication from the several storage areas in the pharmacy inventory. During the bar code conversion process, the study pharmacy built a dedicated repackaging center, which affixed a bar code onto every dose of medication (for example, each individual pill, vial, or ampoule) if the manufacturer had not applied a bar code. In the postbar code period, the prebar code dispensing processes were reorganized into 3 new dispensing processes: 1) carousel fill, 2) alternate zone fill, and 3) 2-day fill (Table 1). Each medication dose was dispensed by only 1 of these processes. For the 3 new dispensing processes, the pharmacy used a different configuration of bar codescanning technology to leverage a combination of internally developed and vendor-supplied software and hardware. Carousel Fill Process The carousel fill process dispensed the compact and nonrefrigeration-requiring forms of commonly used medications for the semi-automated medication cabinets (Sure-Med). These cabinets stored frequently used medications in medication-specific drawers, from which nurses dispensed doses for all patients on a particular unit. The Sure-Med fill process previously dispensed these medications. The new carousel fill process was so named because it used a newly purchased, bar codebased, high-volume storage and retrieval system called the carousel, which also monitored the supply levels in the Sure-Med cabinets to ensure an adequate supply of frequently used medications on each unit. When medications were stocked into the carousel, pharmacy staff scanned 1 dose per batch to ensure that the correct medications were placed in the appropriate compartment. When a pharmacy technician retrieved medications during the filling step, the machine directed the technician to the appropriate storage compartment within the carousel. The technician visually inspected the retrieved medication and scanned the bar code on it to ensure that he or she had retrieved the correct medication. In most cases, the carousel machine would instruct the technician to retrieve several doses of the same medication (a medication batch [see Glossary]) at a time to replenish the supplies for a particular cabinet. In these cases, only 1 dose was scanned. We will use Stock&Retrieve(+) Scan(+) as shorthand to characterize this process (see Glossary). Alternate Zone Process The alternate zone process dispensed commonly used medications that could not be accommodated in the carousel machine because of their size or need for refrigeration. Medications for this process were stocked onto shelves manually. When pharmacy technicians filled medications for this process, they manually retrieved the medications from the shelves, visually inspected them, and scanned their bar codes. Similar to the carousel fill process, if several doses of the same medication were being dispensed, only 1 dose was scanned. We will use Stock&Retrieve() Scan(+) as shorthand to characterize this process (see Glossary). Two-Day Fill Process The 2-day fill process handled less commonly used medications that the first-dose fill and cart fill processes previously dispensed to the patient-specific drawers on patient care units. Medications were stocked manually onto shelves and were retrieved by hand during the filling step. The technician in this process would typically retrieve several doses of the same medication at a time so that the patient-specific drawer in the patient care area would carry a 2-day supply. However, unlike the procedure in the carousel or alternate zone fill process, all doses retrieved in the 2-day fill process had to be scanned. We will use Stock&Retrieve() Scan(++) as shorthand to characterize this process (see Glossary). We excluded one dispensing process, controlled substance fill, which accounted for approximately 16% of daytime, weekday dispensing in the pharmacy, from the study because of limited research personnel and its lower baseline dispensing error rate (4). Measurement of Dispensing Error and Potential ADE Rates The primary outcomes of our study were the rates of target dispensing errors (see Glossary) and target potential ADEs (see Glossary). We used identical methods that were approved by the institutional review board at the study institution to measure the rates of dispensing errors in the prebar