Background: Medication errors commonly involve confusion between drugs with similar names. One possible method of reducing error is to emphasize differences between the names using ‘Tall Man’ (uppercase) letters (e.g. cef-TAZidime vs cefUROxime). Previous studies investigating this issue have been conducted mainly on university students, and results have been mixed.
Objective: To investigate the influence of Tall Man lettering on drug name confusion in other key participant groups.
Study Design: Two separate experiments were conducted. In Experiment 1 (conducted at the University of Glasgow, Scotland, between January 2008 and May 2008), younger and older adults performed a same/different judgement task. In Experiment 2 (conducted at various sites in England between December 2008 and February 2009), healthcare practitioners performed a task based on electronic prescribing.
Results: In Experiment 1, both younger and older adults made fewer name confusion errors when names contained Tall Man letters. Response times suggested that Tall Man lettering drew participants’ attention to those letters, but that readers did not solely rely on these letters in making their response. In Experiment 2, healthcare practitioners made fewer name confusion errors when the names contained Tall Man letters.
Conclusions: Overall, results showed that Tall Man lettering reduced drug name confusion errors in a series of laboratory-based tasks, in both younger and older adults, and healthcare practitioners. Thus, the current findings offer some support for the use of Tall Man letters as a possible systems change that could be made by both pharmacies and manufacturers in an effort to reduce error caused by drug name confusion.
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1Pilot data were collected from a small sample of older adults in order to determine a display time that would equate overall accuracy across age groups, so that patterns of performance could be compared on the same point of the performance scale (i.e. so that older adults were not simply performing at chance level).
2Because of high accuracy scores, in order to reduce the likelihood of a ceiling effect, additional analyses were carried out on a dataset where participants who had scored over 95% correct in all conditions had been removed, resulting in a reduced dataset of 75 participants. Findings were essentially the same as those for the full set of participants. In particular, there was still a significant interaction, F(1 ,74) = 6.99, p < 0.05, $ða_⤪ p^2$ = 0.09, indicating that when the target was absent from the list, participants were less likely to indicate that the target was present (i.e. to confuse a similar distractor for the target) when the name contained Tall Man lettering: F(1,74) = 14.06, p< 0.001, $ða_⤪ p^2$ = 0.16. In contrast, when the target was present, there was no difference between the two conditions: F < 1. This would suggest that significant effects were not simply due to the reduced variance associated with high accuracy scores.
Hoffman JM, Proulx SM. Medication errors caused by confusable drug names. Drug Saf 2003; 26: 445–52
Flynn AF, Barker KN, Carnaham BJ. National observational study of prescription dispensing accuracy and safety in 50 pharmacies. J Am Pharm Assoc 2003; 43: 191–200
NHS Business Services Authority. Update on growth in prescription volume and cost in the year to June 2009 [online]. Available from URL: http://www.nhsbsa.nhs.uk/PrescriptionServices/Documents/Volume_and_cost_year_to_June_2009.pdf [Accessed 2009 Oct 31]
National Pharmacy Association. Similar names [online]. Available from URL: http://www.npa.co.uk/ [Accessed 2009 Apr 20]
Lambert BL, Lin S-J, Tan HK. Designing safe drug names. Drug Saf 2005; 28: 495–512
Cohen MR, editor. Medication errors. Washington, DC: American Pharmaceutical Association, 1999
FDA. Name differentiation project [online]. Available from URL: http://www.fda.gov/Drugs/DrugSafety/MedicationErrors/ucm164587.htm [Accessed 2009 Jun 27]
ISMP. FDA and ISMP lists of look-alike drug name sets with recommended Tall Man letters [online]. Available from URL: http://www.ismp.org/tools/tallmanletters.pdf [Accessed 2009 Jun 27]
Filik R, Purdy KJ, Gale AG, et al. Drug name confusion: evaluating the effectiveness of capital (‘Tall Man’) letters using eye movement data. Soc Sci Med 2004; 59: 2597–601
Filik R, Purdy KJ, Gale AG, et al. Labelling of medicines and patient safety: evaluating methods of reducing drug name confusion. Hum Factors 2006; 48: 39–47
Schell KL. Using enhanced text to facilitate recognition of drug names: evidence from two experimental studies. Appl Ergon 2009; 40: 82–90
Gabriele S. The role of typography in differentiating lookalike/sound-alike drug names. Healthc Q 2006; 9 (Special Issue): 88–95
Ferrini A, Ferrini R. Health in the later tears. 3rd ed. Boston (MA): McGraw Hill, 2000
Wilson IB, Schoen C, Neuman P, et al. Physician-patient communication about prescription medication nonadherence: a 50-state study of America’s seniors. J Gen Intern Med 2007; 22: 6–12
Moisan J, Gaudet M, Grégoire J-P, et al. Non-compliance with drug treatment and reading difficulties with regard to prescription labelling among seniors. Gerontology 2002; 48: 44–51
Daneman M, Merikle PM. Working memory and language comprehension: a meta-analysis. Psychon Bull Rev 1996; 3: 422–33
Verhaegen P, Marcoen A, Goossens L. Facts and fiction about memory aging: a quantitative integration of research findings. J Gerontol 1993; 48: 157–71
Brebion G. Working memory, language comprehension, and aging: four experiments to understand the deficit. Exp Aging Res 2003; 29: 269–301
Just MA, Carpenter PA. A capacity theory of comprehension: individual differences in working memory. Psychol Rev 1992; 98: 122–49
Just MA, Varma S. A hybrid architecture for working memory [reply]. Psychol Rev 2002; 109: 55–65
King J, Just MA. Individual-differences in syntactic processing: the role of working memory. J Mem Lang 1991; 30: 580–602
MacDonald MC, Just MA, Carpenter PA. Working memory constraints on the processing of syntactic ambiguity. Cogn Psychol 1992; 24: 56–98
Price JM. The use of focus cues in healthy aging [dissertation]. Glasgow: the University of Glasgow, 2008
The British Psychological Society Code of Ethics and Conduct [online]. Available from URL: http://www.bps.org.uk/the-society/code-of-conduct/code-of-conduct_home.cfm [Accessed 2010 Jun 6]
Nelson H. National Adult Reading Test (NART). 2nd ed. Berkshire: NFER-Nelson, 1982
National Patient Safety Agency. Improving reporting and learning from medication incidents. London: National Patient Safety Agency, 2009 Sep
Bates DW, Cullen DJ, Laird N, et al. Incidence of adverse drug events and potential adverse drug events: implications for prevention. ADE Prevention Study Group. JAMA 1995; 274: 29–34
Berman A. Reducing medication errors through naming, labeling, and packaging. J Med Syst 2004; 28: 9–29
Léger L, Rouet J-F, Ros C, et al. Impact of the visual appearance of words on visual search within word lists [poster]. Presented at the 49th Annual Meeting of the Psychonomic Society; 2008 Nov 13–16; Chicago (IL)
Reilly S, Grasha AF, Schafer J. Workload, error detection, and experienced stress in a simulated pharmacy verification task. Percept Mot Skills 2002; 95: 27–46
Flynn EA, Barker KN, Gibson JT, et al. Relationships between ambient sounds and the accuracy of pharmacists’ prescription-filling performance. Hum Factors 1996; 38: 614–22
Buchanan TL, Barker KN, Gibson JT, et al. Illumination and errors in dispensing. Am J Hosp Pharm 1991; 48: 2137–45
Flynn EA, Barker KN, Gibson JT, et al. Impact of interruptions and distractions on dispensing errors in an ambulatory care pharmacy. Am J Health Syst Pharm 1999; 56: 1319–25
ISMP. Use of Tall Man letters is gaining wide acceptance [online]. Available from URL: http://www.ismp.org/newsletters/acutecare/articles/20080731.asp [Accessed 2009 Jun 27]
Gerrett D, Gale AG, Darker IT, et al. The use of Tall Man lettering to minimise selection errors of medicine names in computer prescribing and dispensing systems. Report to the UK National Health Service Connecting for Health Initiative. Leeds: National Health Service, 2009. Report no.: ER-07-0612
Day RS. Solving drug name confusions can create new problems [poster]. Presented at the 50th Annual Meeting of the Psychonomic Society; 2009 Nov 19–22; Boston (MA)
No funding was received for the conduct of Experiment 1. Experiment 2 was supported by funding from the UK NHS Connecting for Health initiative. The funding organization specified the issue to be investigated and advised on drug names that are often involved in error, but were otherwise not involved in the conduct of the study, interpretation of results or preparation of the manuscript. David Gerrett received consultancy remuneration to undertake specific tasks for this research. He continues to collaborate with the research team and is now working with the National Patient Safety Agency, which has an interest in furthering knowledge in this area. All other authors have no potential conflicts of interest to declare that are directly relevant to the content of this study.
Electronic supplementary material
Instructions for Producing CD3-Type Tall Man Drug Names
To apply the CD3 Tall Man rule, firstly collect drug names into groups of two or more names that are orthographically similar (in our case, groupings were determined in consultation with the NPSA and NHS Connecting for Health initiative). Then, on a letter-by-letter basis, start from either end of each drug name and work towards the middle; the first letters encountered at either end that differ across at least two drug names in the group, along with all letters occurring between them, are deemed to fall within a critical portion of each drug name and are candidates for capitalization. Capitalize a maximum of only three of these letters per drug name. Where more than three letters are present in the critical portion of the drug name, capitalize the centre most three. Where this would result in letters that are common amongst all the drug names of the group in those positions being capitalized, then capitalize the next most peripheral letters that differ across at least two drug names. The initial letters of proprietary drug names are always capitalized. In order to prevent confusion with a lowercase letter ‘l’ and the capital letter ‘I’, the lowercase letter ‘i’ is not capitalized unless it was the initial letter of a proprietary drug name. Using the CD3 rule, cefixime, cefotaxime, ceftazidime, and cefuroxime would become cefiXime and cefOTAxime, cefTAZidime, cefUROxime.
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Filik, R., Price, J., Darker, I. et al. The Influence of Tall Man Lettering on Drug Name Confusion. Drug-Safety 33, 677–687 (2010). https://doi.org/10.2165/11532360-000000000-00000
- National Health Service
- Simple Main Effect
- Healthcare Practitioner
- Natural Case