Systematic derivation of an Australian standard for Tall Man lettering to distinguish similar drug names

J Eval Clin Pract. 2015 Feb;21(1):85-90. doi: 10.1111/jep.12247. Epub 2014 Oct 19.


Rationale, aims and objectives: Confusion between similar drug names can cause harmful medication errors. Similar drug names can be visually differentiated using a typographical technique known as Tall Man lettering. While international conventions exist to derive Tall Man representation for drug names, there has been no national standard developed in Australia. This paper describes the derivation of a risk-based, standardized approach for use of Tall Man lettering in Australia, and known as National Tall Man Lettering.

Method: A three-stage approach was applied. An Australian list of similar drug names was systematically compiled from the literature and clinical error reports. Secondly, drug name pairs were prioritized using a risk matrix based on the likelihood of name confusion (a four-component score) vs. consensus ratings of the potential severity of the confusion by 31 expert reviewers. The mid-type Tall Man convention was then applied to derive the typography for the highest priority drug pair names.

Results: Of 250 pairs of confusable Australian drug names, comprising 341 discrete names, 35 pairs were identified by the matrix as an 'extreme' risk if confused. The mid-type Tall Man convention was successfully applied to the majority of the prioritized drugs; some adaption of the convention was required.

Conclusion: This systematic process for identification of confusable drug names and associated risk, followed by application of a convention for Tall Man lettering, has produced a standard now endorsed for use in clinical settings in Australia. Periodic updating is recommended to accommodate new drug names and error reports.

Keywords: Tall Man; confusion; drug; errors; look-alike sound-alike; standard.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Australia
  • Humans
  • Medication Errors / prevention & control*
  • Prescription Drugs*
  • Terminology as Topic*


  • Prescription Drugs