Glossary
tall man lettering
Tall man lettering puts capital letters into a drug name — glipiZIDE, glyBURIDE — so two look-alike names stop looking alike. FDA and ISMP each publish a list, and they are not the same list.
Tall man lettering (TML) uses uppercase letters to make two similar drug names look different: glipiZIDE against glyBURIDE, vinBLAStine against vinCRIStine, hydrOXYzine against hydrALAZINE. The technique starts at the left of the name and capitalizes the dissimilar block, because a reader skimming a shelf label reaches the middle and the tail last — the part where look-alike names usually differ.
Two organizations publish lists, and the difference between them is the fact most often tested. FDA started its Name Differentiation Project in 2001 to review reports of name-pair confusion, and when it decides TML is the right fix it asks the manufacturer to revise the label and updates its list — so the FDA list is short, and every entry on it is a name FDA has acted on. ISMP publishes its own, longer list (Look-Alike Drug Names with Recommended Tall Man Letters) which it states is not an official list approved by FDA, and ISMP's list also carries brand names, because a brand can collide with another brand just as easily as a generic can. ISMP's methodology is the CD3 rule — capitalize to the right once two or more dissimilar letters have been met.
TML is one answer to the LASA problem (look-alike/sound-alike names), not the whole answer. Separating the stock on the shelf, changing the order of the letters on a screen, and reading back a verbal order are the other ones, and a question that asks for "a strategy" will accept any of them as long as it actually separates the pair.
Taught in
Related terms
- high-alert medication — A high-alert medication is one that bears a heightened risk of significant harm when it is used in error — insulin, heparin, opioids, concentrated electrolytes. The risk is the harm, not a higher error rate.
- NCC MERP — NCC MERP publishes the Index for Categorizing Medication Errors, which sorts errors into categories A to I by outcome: A is a circumstance that could cause an error, B a near miss, and E to I harm.
Source: PTCB — PTCE Content Outline, effective January 6, 2026 (the KA 1.2 statement "Therapeutic duplications", the KA 2.2 and 2.3 statements on controlled substances and prescription requirements, the KA 4.3 and 4.4 statements on NDC, lot, expiration and returns, and the KA 3.1/3.2 error-prevention statements, quoted verbatim); FDA label and NDC data read through openFDA and DailyMed; ISMP (the high-alert medication definition and the error-prone abbreviation list); USP <795> and <797>; the DEA Pharmacist's Manual (outline accessed 2026-10-03, verbatim; every fact below restates this course's own guides, which carry the per-source citations on their own pages (FDA, ISMP, USP and DEA each publish on its own schedule))