Objective To determine the rate and the primary types of medication dispensing errors detected by pharmacists during implementation of a unit dose drug dispensing system. Setting The central pharmacy at the Percy French military hospital (France). Method The check of the unit dose medication cassettes was performed by pharmacists to identify dispensing errors before delivering to the care units. From April 2006 to December 2006, detected errors were corrected and recorded into seven categories: unauthorized drug, wrong dosage-form, improper dose, omission, wrong time, deteriorated drug, and wrong patient errors. Main outcome measure Dispensing error rate, calculated by dividing the total of detected errors by the total of filled and omitted doses; classification of recorded dispensing errors. Results During the study, 9,719 unit dose medication cassettes were filled by pharmacy technicians. Pharmacists detected 706 errors for a total of 88,609 filled and omitted unit doses. An overall error rate of 0.80% was found. There were approximately 0.07 detected dispensing errors per medication cassette. The most common error types were improper dose errors (n = 265, 37.5%) and omission errors (n = 186, 26.3%). Many causes may probably explain the occurrence of dispensing errors, including communication failures, problems related to drug labeling or packaging, distractions, interruptions, heavy workload, and difficulties in reading handwriting prescriptions. Conclusion The results showed that a wide range of errors occurred during the dispensing process. A check performed after the initial medication selection is also necessary to detect and correct dispensing errors. In order to decrease the occurrence of dispensing errors, some practical measures have been implemented in the central pharmacy. But because some dispensing errors may remain undetected, there is a requirement to develop other strategies that reduce or eliminate these errors. The pharmacy staff is widely involved in this duty.
Impact of findings on practice
The specific position of pharmacists and pharmacy technicians makes them fundamental actors in success of the unit dose drug dispensing system.
Because error is human, medication cassettes need to be checked, in order to detect and correct medication dispensing errors, before delivery to the wards.
The Institute of Medicine report on the quality of care found that over one million injuries and at least 44,000 deaths occurred annually in the USA as a result of medical errors . Therefore, medication errors cause over 7,000 deaths per year in the USA and result in adverse effects in 2% of in-hospital patients. Medication errors are also a major cause of medical errors which can do harm to patients and induce adverse drug events (ADEs) [2, 3]. It represents an important clinical problem possibly occurring at every stage of the drug delivery process, i.e., prescribing, transcribing, dispensing, and administering.
Pharmacy dispensing errors are usually associated with poor safety and inefficient dispensing systems. A review of just a few case reports demonstrates the damaging effect of dispensing errors on patients [4–7]. The hospital pharmacy’s medication dispensing process is also recognized as a source of medication errors and potential ADEs. An appropriate dispensing system is an important tool for the prevention and reduction of medication errors by minimizing dispensing error opportunities in a pharmacy. In 1960, North-American hospital pharmacists developed the unit dose system, aiming to reduce medication error rates, drug costs, losses and thefts, and to improve the productivity of health professionals and the quality of health care [8–10].
French hospitals typically use one of the numerous types of ward stock distribution system. In France unit dose drug dispensing system experiments are generally limited to some wards or some hospitals [11, 12]. Therefore, unlike the typical French situation and in order to achieve the highest possible safety level, we implemented a unit dose drug dispensing system at Percy military hospital in April 2006. Even if it’s recognized that efficiency of a unit dose drug dispensing system is achieved by using pharmacy technicians to fill medication cassettes and pharmacists to check them, it is essential to admit that technicians can make errors during the dispensing process. Previous studies have also reported rates of pharmacy dispensing errors ranging from 0.84% to 2.9% [13–16]. At Percy hospital, because implementing a unit dose drug dispensing system was a novel activity, it was essential to assess the number and types of dispensing errors committed by pharmacy technicians.
Aim of the study
The aim of this 9-month study was to measure the rate of dispensing errors caused by pharmacy technicians and to identify the primary types of medication errors in this setting.
The study was conducted at the 354-bed Percy military hospital in Clamart (France) during a 9-month period (April 2006–December 2006). After the acquisition of specific equipments, a unit dose drug dispensing system was first implemented in April 2006 in the haematology department (19 beds) and then was progressively extended to seven other departments. At the end of the study in December 2006, 178 of the 354 beds (50.3%) benefited from this dispensing system. At the beginning of the study a single pharmacy technician was in charge of filling cassettes. In December 2006, five technicians were involved in this activity. Throughout the study, each technician was attached to one or two wards. The study was performed during pharmacy dispensing time between 8 am to 6 pm from Monday to Friday. The hospital pharmacy routinely delivered daily supply of medicines for inpatients, except on Friday, when the pharmacy delivered 72-h supply of medicines. Every day, medical staffs of the care units brought photocopies of all written physician prescriptions to the central pharmacy. Prescriptions were clinically reviewed, modified if necessary after a contact with the physician or in accordance with pharmacy policy, and then approved by pharmacists. After pharmacists’ approval, a pharmacy technician was in charge of filling cassettes by using the original or modified approved prescription. Drugs were dispensed for 24 h per patient in a unit dose medication cassette made up of four compartments: morning, mid-day, evening and night compartments. Filled medication cassettes were checked by trained pharmacists. In this study, only oral pharmaceutical forms filled in medication cassettes were checked. Two pharmacists were daily involved in the check without being specifically to some wards. Dispensing errors were corrected by pharmacists during the final check, before delivering the cassettes to the care units.
The prescription errors detected by pharmacist during the clinical review were systematically corrected before the filling cassettes process and were not recorded in this study.
For the purpose of this study, a dispensing error was defined as any discrepancy between the original or modified approved written prescription, and the contents of the medication cassette. Thus, if a pharmacist discovered an error during the verification, this error was defined as a dispensing error. Each dose with error was recorded as a dispensing error.
Dispensing errors detected by pharmacists during the final check were classified into seven categories according to the types of errors defined by the American Society of Hospital Pharmacists : unauthorized drug error, wrong dosage-form error, improper dose error, omission error, wrong time error, deteriorated drug error, and wrong patient error.
Data collection and data analysis
During the study, the number of prepared medication cassettes and filled doses were daily recorded by pharmacists. Furthermore, the number and types of dispensing errors detected by pharmacists were directly recorded during the check. A pharmacist coordinator was in charge of data analysis. Each month, the coordinator calculated the medication dispensing error by dividing the total number of erroneous doses by the total of filled and omitted doses. In this setting filled doses were defined as doses placed in medication cassettes by technicians. Omitted doses were defined as doses which should have been filled in medication cassettes but were missing. Besides the coordinator monthly evaluated the types of dispensing errors detected by pharmacists.
Scope of the study
For pharmacists and technicians who took part in this study, it was the first experience of a unit dose drug dispensing system. Pharmacy technicians were aware of the check performed by pharmacists but were not informed of the study and its purpose. During the study, the names of the persons who committed the errors were not documented. In addition, the potential clinical significance of dispensing errors and the type of medications associated with drug errors were not evaluated. Moreover, at the time of this study, the focus was the detection and measurement of errors rather than how they could be prevented.
During the study, 9,719 unit dose medication cassettes were filled by pharmacy technicians and checked by pharmacists. Pharmacists detected 706 errors for a total of 88,609 filled and omitted doses. Technicians’ medication filling accuracy was 99.2% (87,903 out of 88,609 doses filled correctly). An overall error rate of 0.80% was calculated. There were approximately 0.07 detected dispensing errors per medication cassettes. Table 1 provides the dispensing error rate for the period from April 2006 to December 2006. The highest rate was found in June 2006 (0.98%) and the lowest in May and August 2006 (0.61%).
Table 2 provides the types of medication dispensing errors detected by pharmacists. Of the 706 dispensing errors registered, the most common types of errors were improper dose errors (n = 265, 37.5%) and omission errors (n = 186, 26.3%). Wrong dosage-form errors and deteriorated drug errors were the least common errors accounting for 24 (3.4%) of the 706 errors.
Examples of improper dose errors included furosemid 20 mg filled as furosemid 40 mg, levothyroxine 0.025 mg filled as levothyroxine 0.05 mg, and acetaminophen 500 mg filled as acetaminophen 1,000 mg. The main reason for omission errors appeared to be the technicians simply reading the prescription too quickly and omitting an order. Wrong time errors (n = 119, 16.9%) included for example alfuzosine [XATRAL LP®] filled in the morning compartment of the medication cassette instead of the evening compartment as prescribed. Most of the unauthorized drug selections (n = 75, 10.6%) involved sound-alike and look-alike names such as confusion between colimycine [COLIMYCINE®] and colchicine [COLCHICINE®] or between molsidomine [CORVASAL®] and perindopril [COVERSYL®]. All of the deteriorated drug errors (n = 14, 2.0%) were due to filling of expired medication doses. Wrong dosage-form errors (n = 10, 1.4%) included for example dispensing of a non controlled-release formulation of verapamil instead of a controlled-release formulation of verapamil.
With a total of 706 detected errors, the results of this study showed that a wide range of errors occurred during filling of medication cassettes. During the study period, the unit dose drug dispensing system kept expanding but it seems that the increasing in beds and departments did not affect the incidence of the dispensing error rate. Our results are also consistent with those in the literature, although there may be some differences on the study durations or the employed methods. Therefore, Hassal and Daniels, while examining three control chart methods used to detect errors in a unit dose dispensing system, reported a mean technician error rate of 2.1% . Taylor and Gaucher found the overall error rate to be 1.7 errors for every 100 orders filled . In their study, the percentage error rate did not increase significantly during the busier times of the day. However, rates varied between the wards, ranging from 0.4% to 4.5%. In our study, no attempt was made to assess these criteria. Klein et al. compared error rates for a manual dispensing system and an automated one and found error rates of 0.84% and 0.65%, respectively . During a 2-week study of dispensing errors identified at the pharmacy’s final check stage, Beso et al. found a 2.7% error rate . In a study by Cina et al., 5,075 pharmacy errors were made out of a total of 140,755 doses filled by pharmacy technicians corresponding to an overall pharmacy dispensing error rate of 3.6% . This overall error rate could be broken down into 2.9% due to technicians’ errors when filling prescriptions, which were detected during the pharmacist verification step, and 0.7% due to errors intercepted after the pharmacist verification step.
In our study, the most common error types were improper dose and omission errors. These findings are in line with previous studies indicating that improper dose and omission errors are among the most frequent error types occurring at the dispensing stage [14, 19]. One possible explanation is that technicians perform an incomplete or rushed reading of the prescription during the filling process. Even though they represented only 10.6% of the total, unauthorized drug errors must be regarded with a particular attention owing to their potential clinical significance . Several studies have reported that many factors may easily explain the presence of errors in the dispensing process such as such as communication failures, working environment or distractions [18, 21]. Furthermore, most preventable injuries are not due to just one system failure but result from breakdown at several points in the dispensing system.
Incontestably, our results showed that a check performed after the initial medication selection is necessary. It provides ongoing benefits by reducing the occurrence of all dispensing-related potential ADEs. Therefore, detection of medication errors must be a component of the pharmacy’s routine quality improvement process and strategies to reduce the occurrence of dispensing errors should target both stages of the drug delivery process. In our unit dose drug dispensing system, it was relatively easy to determine the dispensing error rate. In consequence, the evaluation and the monitoring of this rate may become a relevant quality indicator.
Compared with other studies, the 0.80% error rate calculated in our study may be regarded as an acceptable error rate. Even though it seems realistic to maintain an error rate above 2%, a zero error rate must be the ideal goal of the Percy pharmacy department. In order to near this ambitious target, the central pharmacy at Percy hospital now implements some of the recommendations of the National Coordinating Council for Medication Error Reporting and Prevention . For example, the noise level is reduced, and the check of the medication cassettes is performed in a different area from the filling.
In addition, the results of our study and the major factors contributing to the occurrence of dispensing errors have been presented to the pharmacy technicians. Trainings of pharmacy technicians about medication errors and drug iatrogenic disease represent a very interesting tool to improve the quality of the dispensing process. In order to reduce unauthorized drug errors, incorrect dosage-form errors and deteriorated drug errors, technicians are reminded to perform an attentive reading of dosing instructions. In addition, technicians and pharmacists share now information about errors detected after the filling process in order to prevent future errors.
Even though medication cassettes are checked by pharmacists and a second time by nurses before drug administering, undetected dispensing errors may threaten patients . In order to decrease the number of neglected dispensing errors, adding a second pharmacist verification step could be an option. But this proposition may delay the delivery of medication cassettes to the clinical units.
Another strategy is the delegation of the check to the pharmacy technicians. Several studies have shown that pharmacy technicians are able to verify medications in a unit dose drug dispensing system without compromising the dispensing accuracy [24–28]. At Percy hospital, pharmacists spend at least one hour per day for the check. Delegating this task to technicians should allow the pharmacists to spend additional time for clinical activities and should undeniably represent an economic benefit. Therefore, clinical pharmacists have the opportunity to better control medication errors and to enhance the quality and the safety of therapy prescribed and dispensed to hospitalized patients .
Reducing dispensing errors depends also on research into their causes. The identification of failures in the unit dose drug dispensing system and a systematic analysis of factors contributing to dispensing errors should allow us to improve the dispensing process. The underlying causes of dispensing errors would also represent an interesting area for future studies.
Although causes of dispensing errors were beyond the scope of our study, it seems likely that poor handwriting prescription might have been a major source of error. Ambiguous, incomplete or confusing prescriptions may lead to poor understanding of fundamental information for correct drug delivery. At Percy hospital, the next implementation of a computerized prescribing and dispensing system would improve the reading and understanding of medical prescriptions. Even though Weant et al. observed an increase in the number of medication errors during the initial period following the implementation of a computerized prescribing system, several studies have shown a decreasing error rate in a computerized physician order entry context [30–33]. A computerized prescribing and dispensing system will represent an interesting and promising challenge to reduce the number of dispensing errors.
Finally, it is advisable to indicate that automated medication dispensing systems and bar-code technology may reduce pharmacy dispensing error rates [15, 34–36]. But these solutions are not yet priorities at Percy hospital.
Even if direct observation is recognized as an efficient method in detecting medication errors, our study results should be interpreted with some limitations . It relied in particular on human checkers, who might have failed to detect some dispensing errors. Cina et al. found that pharmacists could only intercept approximately 80% of the errors committed by pharmacy technicians . In a 4-month study, Facchinetti et al. reported that pharmacists failed to detect 12.3% of the 812 artificially errors introduced into the drug distribution system . In consequence, the number of total errors in our study is probably not known with certainty. Furthermore, our study was limited to the oral pharmaceutical forms filled in medication cassettes. Dispensing errors due to other drug forms such as intravenous dosage forms, eye drops or creams were not evaluated. These limitations would tend to underestimate the real rate of dispensing errors.
This 9-month study of dispensing errors detected by pharmacists during the check of medication cassettes found an overall error rate of 0.80%. Despite some differences on the employed methods, this result was similar to previous studies indicating that a wide range of errors occurred during filling of medication cassettes. Improper dose errors and omission errors were the most frequent error types occurring at the dispensing stage. The results of this study prove that the check performed by pharmacists is incontestably necessary aiming to increase the drug safety.
In practice, at Percy hospital, this work has had several impacts. Pharmacy technicians were also made aware of the existence of dispensing errors and their potential consequences. In order to decrease the occurrence of dispensing errors, some practical measures have been implemented in the central pharmacy.
But because it has been shown that pharmacists and nurses failed to detect many dispensing errors that potentially reach the patients, the unit dose drug dispensing system at Percy hospital requires further improvements to minimize or even eliminate medication dispensing errors. Therefore, the delegation of the check to trained pharmacy technicians will allow pharmacists to provide more medication safety initiatives and the next implementation of a computerized prescribing and dispensing process may be considered as a promising challenge. Further studies should also assess the efficiency of these measures.
Kohn LT, Corrigan JM, Donaldson MS. To err is human: building a safer health system. Washington, DC: Committee on Quality of Health Care in America, Institute of Medicine, National Academy Press; 2000.
Phillips DP, Christenfeld N, Glynn LM. Increase in US medication-error deaths between 1983 and 1993. Lancet. 1998;351:643–4. doi:10.1016/S0140-6736(98)24009-8.
Ferner RE, Aronson JK. Medication errors, worse than a crime. Lancet. 2000;355:947–8. doi:10.1016/S0140-6736(00)99025-1.
Scala-Barnett DM, Donoghue ER. Dispensing error causing fatal chlorpropamide intoxication in a nondiabetic. J Forensic Sci. 1986;31:293–5.
Henderson J, Anderson WD, Jawad A. Potassium permanganate burn due to a dispensing error. Burns. 2003;29:401–2. doi:10.1016/S0305-4179(02)00279-6.
Carriere B, Bailey B, Chabot G, Lebel D. Dispensing error leading to alendronate ingestion. Ann Pharmacother. 2003;37:87–9. doi:10.1345/aph.1C217.
Mein E, Sii F, Shah P. An ocular medication dispensing error. Br J Clin Pharmacol. 2006;62:715–6. doi:10.1111/j.1365-2125.2006.02646.x.
Parker PF. Drug distribution in hospitals. Unit-dose systems reduce error, increase efficiency. Hospitals. 1968;42:65–72.
McConnell WE, Barker KN, Garrity LF. Dispensing: report of a study. Am J Hosp Pharm. 1961;18:531–41.
Lepinski PW, Thielke TS, Collins DM, Hanson A. Cost comparison of unit dose and traditional drug distribution in a long-term-care facility. Am J Hosp Pharm. 1986;43:2771–9.
Fontan JE, Maneglier V, Nguyen VX, Loirat C, Brion F. Medication errors in hospitals: computerized unit dose drug dispensing system versus ward stock distribution system. Pharm World Sci. 2003;25:112–7. doi:10.1023/A:1024053514359.
Arnaud L, Coyral D, Dufauret C, Fernandez B, Vergne-Salle P, Bonnet C, et al. A propos d’une expérience d’organisation de dispensation journalière individuelle nominative (DJIN). Actualités pharmaceutiques hospitalières. 2005;1:37–44.
Hassal TH, Daniels CE. Evaluation of three types of control chart methods in unit dose error monitoring. Am J Hosp Pharm. 1983;40:970–5.
Taylor J, Gaucher M. Medication selection errors made by pharmacy technicians in filling unit dose orders. Can J Hosp Pharm. 1986;39:9–12.
Klein EG, Santora JA, Pascale PM, Kitrenos JG. Medication cart-filling time accuracy, and cost with an automated dispensing system. Am J Hosp Pharm. 1994;51:1193–6.
Cina JL, Gandhi TK, Churchill W, Fanikos J, McCrea M, Mitton P, et al. How many hospital pharmacy medication dispensing errors go undetected? Jt Comm J Qual Patient Saf. 2006;32:73–80.
American society of hospital pharmacists. ASHP guidelines on preventing medication errors in hospitals. Am J Hosp Pharm. 1993;50:305–14.
Beso A, Franklin BD, Barber N. The frequency and potential causes of dispensing errors in a hospital pharmacy. Pharm World Sci. 2005;27:182–90. doi:10.1007/s11096-004-2270-8.
Anacleto TA, Perini E, Rosa MB, Cesar CC. Drug-dispensing errors in the hospital pharmacy. Clinics. 2007;62:243–50. doi:10.1590/S1807-59322007000300007.
Rolland P. Occurrence of dispensing errors and efforts to reduce medication errors at the Central Arkansas Veteran’s Healthcare System. Drug Saf. 2004;27:271–82. doi:10.2165/00002018-200427040-00004.
Anacleto TA, Perini E, Rosa MB, Cesar CC. Medication errors and drug-dispensing systems in a hospital pharmacy. Clinics. 2005;60:325–32. doi:10.1590/S1807-59322005000400011.
National Coordinating Council for Medication Error Reporting and Prevention. Recommendations to enhance accuracy of dispensing medications. 1999, 2005. Available from http://www.nccmerp.org/council/council1999-03-19.html.
Leape LL, Bates DW, Cullen DJ, Cooper J, Demonaco HJ, Gallivan T, et al. Systems analysis of adverse drug events. JAMA. 1995;274:35–43. doi:10.1001/jama.274.1.35.
Becker MD, Johnson MH, Longe RL. Errors remaining in unit dose carts after checking by pharmacists versus pharmacy technicians. Am J Hosp Pharm. 1978;35:432–4.
Woller TW, Stuart J, Vrabel R, Senst B. Checking of unit dose cassettes by pharmacy technicians at three Minnesota hospitals. Am J Hosp Pharm. 1991;48:1952–6.
Ness JE, Sullivan SD, Stergachis A. Accuracy of technicians and pharmacists in identifying dispensing errors. Am J Hosp Pharm. 1994;51:354–7.
Spooner SH, Emerson PK. Using hospital pharmacy technicians to check unit dose carts. Hosp Pharm. 1994;29:433–7.
Ambrose PJ, Saya FG, Lovett LT, Tan S, Adams DW, Shane R. Evaluating the accuracy of technicians and pharmacists in checking unit dose medication cassettes. Am J Health Syst Pharm. 2002;59:1183–8.
Scarsi KK, Fotis MA, Noskin GA. Pharmacist participation in medical rounds reduces medication errors. Am J Health Syst Pharm. 2002;59:2089–92.
Weant KA, Cook AM, Armitstead JA. Medication-error reporting and pharmacy resident experience during implementation of computerized prescriber order entry. Am J Health Syst Pharm. 2007;64:526–30. doi:10.2146/ajhp060001.
Bobb A, Gleason K, Husch M, Fienglass J, Yarnold PR, Noskin GA. The epidemiology of prescribing errors: the potential impact of computerized prescriber order entry. Arch Intern Med. 2004;164:785–92. doi:10.1001/archinte.164.7.785.
Mirco A, Campos L, Falcao F, Nunes JS, Aleixo A. Medication errors in an internal medicine department. Evaluation of a computerized prescription system. Pharm World Sci. 2005;27:351–2. doi:10.1007/s11096-005-2452-z.
Van Gijssel-Wiersma DG, Van den Bemt PM, Walenbergh-Van Veen MC. Influence of computerised medication charts on medication errors in hospital. Drug Saf. 2005;28:1119–29. doi:10.2165/00002018-200528120-00006.
Kratz K, Thygesen C. A comparison of the accuracy of unit dose cart fill with the Baxter ATC-212 computerized system and manual filling. Hosp Pharm. 1992;27:19–20.
Scott O, Caldwell R. Dispensing error rate after implementation of an automated pharmacy carousel system. Am J Health Syst Pharm. 2007;64:1427–31. doi:10.2146/ajhp060636.
Poon EG, Cina JL, Churchill W, Patel N, Featherstone E, Rothschild JM, et al. Medication dispensing errors and potential adverse drug events before and after implementing bar code technology in the pharmacy. Ann Intern Med. 2006;145:426–34.
Flynn EA, Barker KN, Pepper GA, Bates DW, Mikeal RL. Comparison of methods for detecting medication errors in 36 hospitals and skilled-nursing facilities. Am J Health Syst Pharm. 2002;59:436–46.
Facchinetti NJ, Campbell GM, Jones DP. Evaluating dispensing error detection rate in a hospital pharmacy. Med Care. 1999;37:39–43. doi:10.1097/00005650-199901000-00007.
The authors wish to acknowledge all the pharmacy technicians who took part in this study.
No financial support was received.
Conflict of interests
No conflict of interests to declare.
About this article
Cite this article
Bohand, X., Aupée, O., Le Garlantezec, P. et al. Medication dispensing errors in a French military hospital pharmacy. Pharm World Sci 31, 432–438 (2009). https://doi.org/10.1007/s11096-009-9290-3
- Dispensing error
- Hospital pharmacy
- Medication error
- Military hospital
- Unit dose dispensing