Hospital drug distribution systems in the UK and Germany ‐ a study of medication errors

The aim of this study was to compare the incidence of medication errors and the stages of the drug distribution system at which they occur in a United Kingdom (UK) hospital using the ward pharmacy system, a German hospital using the unit dose system

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  that error rates had decreased in each country [67].Since that time, research into medication errors hascontinued to develop, and observation of medicationpreparation and administration has become acceptedas the most reliable method of identifying medicationerrors [8].Little medication error research has been carriedout elsewhere in Europe. A small number of studieshave been published, but the standard observation-based method was not used and the results are there- fore difficult to interpret [9-12]. For example, the firstGerman medication error study included errors in therecording of verbal orders, other documentationerrors and administration errors, and the results donot distinguish between them [13]. This study had lit-tle impact as the error rate of 4.6% was not consid-ered high and only minor changes to the traditionaldrug distribution system were suggested. Other stud-ies have since been carried out in German hospitals,[14-16] but none have used the standard observa-tion-based method. Recently, some hospitals in Germany have begunto implement unit dose systems [1718]. Reasons for themove to unit dose drug distribution include short-ages of nursing staff and desire to reduce risk, reducecosts and increase pharmacists’ involvement withdrug therapy [19]. However, although the unit dosesystem was shown to decrease medication errors inthe USA in the 1960s, it cannot be assumed that thiswill also apply to other health care cultures in the1990s. It is not known how the medication error ratesof the traditional and unit dose systems in Germanycompare with each other or with other drug distribu-tion systems such as the ward pharmacy system. We therefore decided to measure the medicationerror rate in a UK hospital using the ward pharmacysystem, a German hospital using the traditionalsystem and a German hospital using the unit dosesystem. In previous studies, medication errors havegenerally been classified according to type (wrongdrug, wrong dose, etc.) [8]. However, this taxonomyis not helpful in identifying the causes of errors or how they can be prevented. We therefore decided todetermine the stages of each system in which medi-cation errors srcinated, in order to identify the mostvulnerable stages and suggest strategies to reduceerrors. Previous medication error studies have beencriticised for failing to consider the importance of theerrors identified [20]; we therefore included a meas-ure of clinical severity. Methods Definitions Definitions were based on those of Allan and Barker [8]. A medication error was defined as a dose of medi-cation administered to a patient that deviated fromthe doctor’s prescription. Wrong time errors and pre- Arti  c l e s Introduction In any hospital, a drug distribution system is requiredto supply the medication prescribed for each inpa-tient. The drug distribution system includes all theprocesses that occur between the prescription of adrug and the administration of that drug to thepatient. There are many varieties of drug distributionsystem in use throughout the world, but all have thesame goal: to ensure that each dose of medicationadministered to each patient is exactly that which wasintended by the prescriber. A measure of the qualityof any drug distribution system is the incidence of medication errors, where a medication error is anydiscrepancy between the medication prescribed andthat administered.The first studies of medication errors were carriedout in the United States of America (USA) [1] and theUnited Kingdom (UK) [23] in the 1960s. Very highrates of errors were identified, prompting the devel-opment of different drug distribution systems in eachcountry. UK hospitals adopted the ward pharmacysystem [4] and in the USA, the unit dose system wasintroduced [5]. Subsequent research demonstrated V  ol   um e 2 1 Nr  .1 1  9  9  9  P  h  a  r  m a  c  y W o  r  l   d  & S  c  i   e  n c  e  25 Hospital drug distribution systems in the UK and Germany - a study of medication errors •Katja Taxis, Bryony Dean and Nick Barber  Pharm World Sci 1999;21(1): 25-31. ©1999 Kluwer Academic Publishers. Printed in the Netherlands. Katja Taxis (correspondence) , Bryony Dean and Nick Barber: Centre for Pharmacy Practice, The School of Pharmacy, 29-39 Brunswick Square, London, WC1N 1AX, UK.Email: Keywords Drug distribution systemMedication errorsTraditional drug distribution systemUnit dose system Ward pharmacy system  Abstract The aim of this study was to compare the incidence of medication errors and the stages of the drug distributionsystem at which they occur in a United Kingdom (UK)hospital using the ward pharmacy system, a German hospitalusing the unit dose system and a German hospital using their traditional system. Medication errors were identified byobserving the preparation and administration of regularlyscheduled solid oral medication.In the UK hospital using the ward pharmacy system, themedication error rate was 8.0% (95% confidence interval6.2-9.8%). The majority of these errors occurred at the stageof medication administration. In the hospital using the traditional German system, the error rate was 5.1% (4.4-5.8%). With the German unit dose system, the error rate was 2.4% (2.0-2.8%). In both German systems theerrors were mainly attributable to the stage of transcription. It was noted that patient turnover was much higher in thewards using the ward pharmacy system and therefore thestudy sites may not be comparable. However,recommendations can be made in order to reduce the error rate associated with each system. Errors associated with theward pharmacy system may be reduced if medication isstored in individual patient medicine cabinets and patients’own drugs used. Errors occurring with the traditional systemand the unit dose system may be reduced if the srcinalprescription is used for medication administration. Accepted March 1998  scribing errors were not included, however prescrip-tions that were illegible or ambiguous were includedas a source of error.The denominator used to calculate the medicationerror rate  was the total number of opportunities for error (OE). An opportunity for error  was defined as anydose administered or any dose prescribed but omit-ted. Doses were only included as OE if the researcher had observed their preparation and could determinewhether or not a medication error had occurred.Doses of medication placed at patients’ bedsideswere included as OE even if their consumption by thepatient was not observed. Study sites The study was carried out between May and July1997 at an 850 bed UK hospital using the ward phar-macy system, a 600 bed German hospital using thetraditional drug distribution system and an 880 bedGerman hospital using the unit dose system. At the UK hospital, doctors prescribed medicationdirectly onto patients’ drug charts [21]. About 80% of the drugs needed on each ward were kept as wardstock; the remainder were dispensed for individualpatients. Each ward was visited by a designated phar-macist twice daily from Monday to Friday and onceon Saturdays, who initiated the supply of any non-stock drugs required. Each day, the pharmacist alsochecked that all prescriptions were legal, unambigu-ous and clinically appropriate. The pharmacy wasopen Monday to Friday 8:30 am until 5:30 pm andon Saturday and Sunday mornings. A resident phar-macist was available at all other times. Nurses admin-istered medication using a drug trolley which waswheeled from bed to bed during each of the four daily drug administration rounds. The drug chart,kept at the end of each bed, was used to determinethe drugs to be administered and to record their administration.In the hospital using the traditional Germansystem, each ward kept a large floor stock of formu-lary drugs which were ordered from the pharmacydepartment twice a week by nursing staff. The phar-macy was open Monday to Friday 7:30 am until 4pm; an on-call pharmacist was available at all other times. Pharmacists visited each ward twice a year.Doctors prescribed medication in a section of thepatient’s medical notes that was also used to giveother instructions to the nurses. The doctor set acoloured marker on the patient’s notes to indicate tothe nursing staff the presence of a new prescription.Nursing staff then transcribed the prescriptions ontodrug administration charts in the patient’s notes.Prescriptions for regularly administered oral medica-tion were transcribed at the same time onto a drugadministration card for each patient. Each patient’sdrug administration card was placed under the plasticcover of their section of a drug administration tray,and was used by nurses to prepare medication in thedrug preparation room for each of the four daily drugrounds. The administration of medication was notrecorded.The second German hospital studied had started toimplement a unit dose system three years previously. Wards using the unit dose system were visited by apharmacist twice a day. The pharmacy was open 7am until 7 pm on weekdays and 8 am until 3 pm onSaturdays. At other times, an on-call pharmacist wasavailable. On admission, medication was prescribedon patients’ admission sheets. Subsequent changeswere written on sheets filed in the patient’s notes, asin the traditional system. Either a nurse or a pharma-cist could enter prescriptions into the computer system although all entries had to be verified by apharmacist before they could be dispensed. Patientmedication profiles were printed after each changeand filed in patients’ notes. Medication was dis-pensed every 24 hours in the pharmacy departmentusing a Baxter ATC 212 automated tablet counter.Unit dose packages were automatically labelled withpatient name and room number, drug details andtime of administration, before being placed by tech-nicians into individual patient drawers in a drug trol-ley. A pharmacist then checked the dispensed medi-cation before its delivery to the ward. A range of drugs was kept as ward stock and could be used toadminister urgent medication. Four drug roundswere carried out each day; administration of medica-tion was not documented. Data collection Information on patient numbers was obtained at eachsite, so that the characteristics of the wards studiedcould be compared.Medication errors were identified using an observa-tion-based method [1] on two adult wards at eachsite. On each ward, a researcher (BD or KT in the UK;KT in both German hospitals) attended every drugadministration round scheduled for the weekdays of one week and observed the preparation and adminis-tration of regularly scheduled solid oral doses of med-ication. It was anticipated that this data collectionschedule would allow the observation of 1000 OE ateach site, a sample size calculated to be sufficient toconclude that a difference in error rates of 3% wasstatistically significant ( a = 0.05; b = 0.2) within therange of error rates expected [22]. The researcher recorded details of each dose that was administeredand compared these with the srcinal prescription toidentify any discrepancies. This comparison tookplace concurrently in the UK hospital where the srci-nal prescription was used for medication administra-tion, and retrospectively in both German hospitalswhere srcinal prescriptions were not used for admin-istration. Since errors were identified concurrently inthe UK hospital, for ethical reasons the researcher intervened to prevent the occurrence of any error that was considered harmful; such incidents wereincluded as medication errors. However if the nurse or patient prevented an error from occurring this wasnot counted as a medication error. Nursing staff ateach site were informed that the aim of the study wasto identify the advantages and disadvantages of dif- ferent drug distribution systems. Approval for thestudy was obtained from hospital management ateach site.In the hospital using the traditional Germansystem, the administration of medication to individualpatients could not be observed because three or morenurses administered medication at once. However thepreparation of each dose was observed; it wasassumed that no changes to the medication occurredafter the nurses left the drug preparation room. P  h  a  r  m a  c  y W o  r  l   d  & S  c  i   e  n c  e  V  ol   um e 2 1 Nr  .1 1  9  9  9  26  Data analysis The percentage incidence of medication errors wascalculated for each site, and for each researcher at theUK hospital. Ninety-five percent confidence intervalswere calculated for error rates and their differences[23]. If the 95% confidence interval (CI) for the differ-ence between two error rates does not include zerothen the difference is statistically significant. Themedication errors identified were classified accordingto mutually exclusive categories of type (Appendix 1)and the stage of the system in which they occurred(Appendix 2). The number of failures in each drugdistribution system was also calculated. One failureincluded all medication errors that had the same ori-gin and occurred to the same patient. For example,the incorrect transcription of a prescription can beconsidered to be one failure in the drug distributionsystem, regardless of how many medication errorsresult. The potential significance of each system fail-ure was assessed using a severity scale developed atthe London School of Pharmacy [24]. This is an objec-tive scale which takes into account the legal classifica-tion and the therapeutic index of the drug con-cerned, the number of errors resulting from each fail-ure in the system, whether the error resulted in thedrug being used outside its product license and thelikelihood of any serious adverse effect. Each of these factors is scored, and then added to produce an over-all score. Scores range from 0 to 100; a score of lessthan 50 is considered to be of minor severity. Twopharmacists each carried out the scoring indepen-dently. Results Characteristics of the wards studied are shown inTable 1. Error rates identified at each site are summar-ised in Table 2. In the UK hospital, all scheduled drugrounds were observed during the study period, how-ever on one ward two nurses sometimes administeredmedication at the same time using two drug trolleys;in such cases medication preparation and administra-tion for only half of the patients could be observed. Inthe hospital using the traditional system 30 out of 40scheduled drug rounds were observed; it was notpossible to include the night time drug rounds asnurses prepared medication while carrying out other duties. However, only about 8% of the daily medica-tion was administered during this round. In the hospi-tal using the unit dose system 36 out of 40 scheduleddrug rounds were observed. The observer missed the first drug rounds on each ward due to a delay in intro-ducing the study to ward staff.The error rates for the three systems were found tobe significantly different to each other. The 95% CI for the difference between the error rates of the ward pharmacy system and the traditionalsystem was 0.6% to 5.2%. The 95% CI for the differ-ence between the ward pharmacy system and theunit dose system was 3.6% to 7.6%. The 95% CI for the difference between the two German hospitals was1.1% to 4.3%. Figures 1 and 2 show the errors ana-lysed according to type and the stage of the system inwhich they srcinated.Table 3 shows the numbers of OE and errors identi- fied by each observer in the UK hospital. The differ-ence in the error rates identified by each researcher isnot significant (95% CI for the difference -0.7% to6.7%).The medication errors identified resulted from 50 failures in the drug distribution system in the UK hos-pital, 23 in the German hospital using the traditionalsystem and 20 in the German hospital using the unitdose system. The severity scores for these are shownin Figure 3; the two researchers agreed on the scoresin 100% of cases. Discussion Rates and types of errors Significantly different medication error rates wereidentified in the three hospitals studied. The unit dosesystem was associated with the lowest error rate andthe ward pharmacy system with the highest. As wellas having different overall error rates, the threesystems were associated with different types of error that occurred in different stages of the drug distribu-tion system.The predominant type of error associated with the V  ol   um e 2 1 Nr  .1 1  9  9  9  P  h  a  r  m a  c  y W o  r  l   d  & S  c  i   e  n c  e  27 Table 1 Comparison of wards during the study period  Ward pharmacy system Traditional system Unit dose systemWard General General General Rehabilitation Respiratory Urology medical medical surgical  Beds282032303037Mean LOS a bed occupancy90%94%53%88%86%96% Admissions1621431310Discharges16218278Nursing staff morning653-463-44-5afternoon4-553633evening341111Solid oral doses389454256717778540Doses/patient day6.24.835.44.93.75 a LOS = length of stay in days.  ward pharmacy system was omission. At the orderingstage these were mainly due to unavailability of non-stock drugs; at the administration stage these weremainly due to nurses missing doses on the drug chartand not being able to locate medication in the drugtrolley. In particular, nurses had problems findingstock drugs that were prescribed by generic name butwere supplied in manufacturer’s srcinal packs withbrand names, such as doxazosin (supplied asCardura ® ) and enalapril (supplied as Innovace ® ).Other errors also occurred at the administration stagewhere nurses selected the incorrect preparation.Such errors suggest training needs amongst nursingstaff. For example, on several occasions thiamine tab-lets were selected instead of vitamin B compoundstrong, and plain carbamazepine tablets were select-ed where modified release tablets were prescribed.On other occasions, modified release carbamazepinetablets were crushed prior to administration, againsuggesting training needs.In the German hospital using the traditionalsystem, the main types of errors were omission errors,wrong dose errors and extra dose errors. About half of the omissions were due to unavailability of non-for-mulary medication. Other omission errors and extradose errors were due to incorrect or delayed tran-scription. For example, in one case a patient was pre-scribed co-beneldopa but did not receive any duringthe study period as the prescription was not tran-scribed onto the patient’s drug administration card.In other cases doses were apparently not noticed onthe drug administration cards. The majority of thewrong dose errors that occurred with the traditionalsystem were due to the transcription of prescriptions for 15 millilitres of paracetamol suspension (750 mg)as a 500 mg tablet.The most common type of error that occurred inthe unit dose system was omission. These mainly src-inated in the transcription stage, where transcriptionwas either delayed or did not occur. Errors in the tran-scription stage also resulted in some wrong drug andwrong dose errors. The remaining omission errorsoccurred in the administration stage, where doseswere sometimes left in patients’ drawers in the drugtrolley. P  h  a  r  m a  c  y W o  r  l   d  & S  c  i   e  n c  e  V  ol   um e 2 1 Nr  .1 1  9  9  9  28The severity scores were similar for the system fail-ures that occurred at each site, and suggest that themajority were relatively minor in nature.The error rate in the UK hospital was surprisinglyhigh. Error rates of between 2.8% and 5.7% [21 25-29] have previously been reported for UK hospitalsusing the ward pharmacy system. Furthermore, oneof the previous studies cited [21] was carried out atthe same hospital as the present study using identicalmethods and identical medication error definitions;the two general medical wards studied had an overallmedication error rate of 2.0%. In the four year periodbetween the two studies, patient turnover hasincreased considerably and this is one factor that mayhave contributed to the increase in error rates. Ho etal. [28] found that medication error rates were higher in the first 48 hours after prescribing and the first 48hours after patient admission. Wards with a higher patient turnover will have a higher proportion of patients in these higher risk categories. Limitations to the study  We were not able to include intravenous, ‘asrequired’, liquid, inhaled or controlled drugs in thestudy. This was because these drugs were adminis-tered separately to the main drug rounds in one or more of the hospitals studied. The error rate associat-ed with these types of medication is therefore notknown. We also excluded weekends. Ho et al. [28] found that the error rate on a care of the elderly wardwas significantly lower during weekends than week-days. However it is not known whether this finding isgeneralisable to other wards and other drug distribu-tion systems. Future studies should therefore includeweekends.The method used in this study has an inherent limi-tation: the effect of the observer on the observednurse. Although any such effect would be difficult tomeasure, the same method was used in each of thethree hospitals and any effect should be equal ineach. Alternative methods of identifying medicationerrors have been shown to be unreliable [1 30] andobservation therefore remains the method of choice.There were wide variations between wards in meanlength of stay, percentage bed occupancy and num- Table 2 Opportunities for error and medication errors observed at each site  Opportunities for errorMedication errorsError rate (95% CI  a   )  Ward pharmacy system842678.0% (6.2% - 9.8%)Traditional system973505.1% (4.4% - 5.8 %)Unit dose system1318322.4% (2.0% - 2.8%) a CI = confidence interval. Table 3 Opportunities for error and medication errors identified by each observer in the hospital using the ward pharmacy system ResearcherOpportunities for errorMedication errorsError rate (95% CI  a   ) BD411399.5% (6.7% - 12.3%)KT431286.5% (4.2% - 8.8%) a CI = confidence interval.  V  ol   um e 2 1 Nr  .1 1  9  9  9  P  h  a  r  m a  c  y W o  r  l   d  & S  c  i   e  n c  e  29 Figure 1 Medication errors analysed according to type. Figure 2 Medication errors analysed according to the stage of the system in which they occurred. Figure 3 Severity scores for the failures in each drug distribution system.
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