Building and Maintaining a Look-Alike/Sound-Alike (LASA) Medication List

A look-alike/sound-alike (LASA) medication list is a risk-management tool, not a typography convention. Tall man lettering is one item on it — a way of formatting a small number of the names on the list so they read differently on a screen or label. The list itself is broader: it is the institution’s own inventory of which drug name pairs in its own formulary are confusable enough to warrant a safeguard, and it exists whether or not any single pair on it ever gets tall man letters applied. Building and maintaining that list, and matching each entry to a real mitigation, is a separate job from the lettering rule, and it is the job this page covers.

This page is written for the people who own that list at a hospital: patient-safety officers, quality directors, risk managers, and the pharmacy/medication-safety staff who maintain it day to day. It covers where the ISMP list that most programs start from actually comes from, how to turn it into a list of the pairs your institution actually stocks, and the mitigation strategies specific to LASA risk — storage separation, order-entry safeguards, and independent double-checks — that do the load-bearing work once a pair is on the list. Where tall man lettering fits, it fits as one of several tools, covered here only by reference; the CD3 capitalization rule, the per-surface rendering failures, and the mixed experimental evidence on lettering specifically are covered in full in Tall Man Lettering: Two Different Lists, the CD3 Rule, and Making It Hold Across Every Screen, and this page does not repeat them.

Where the list comes from, and what it actually contains

The document most US programs start from is the ISMP List of Confused Drug Names, published by the Institute for Safe Medication Practices (ISMP), now hosted through ISMP’s parent organization ECRI. It is a name-pair list drawn from ISMP’s own medication-error reporting programs and from FDA guidance, and it is broader in kind than the tall man lettering list specifically: it includes generic-generic pairs, brand-generic pairs, and brand-brand pairs, and it flags which entries already carry an FDA-approved or ISMP-recommended tall man rendering and which do not. A meaningful share of the pairs on it have no tall man treatment at all — the confusability comes from how the names sound when spoken as a verbal order, how they look in handwriting or a truncated display field, or how similar their packaging and dosing context are, not from letter shape.

Two things about the source document matter operationally. First, it is a gated download — obtaining it requires registration through ECRI’s ISMP resources site, and legacy ismp.org links to it now redirect there. Get it from ISMP/ECRI directly rather than relying on a third-party reproduction, and check the version date each time, since it is revised periodically. Second, it is explicitly not the same document as the ISMP List of High-Alert Medications. High-alert status is about the severity of harm if an error occurs with a drug at all — insulin, opioids, anticoagulants, concentrated electrolytes — regardless of whether that drug’s name resembles another one. LASA status is about name confusability specifically. The two lists overlap in places (insulin products are both high-alert and heavily represented on the LASA list, since NovoLIN/NovoLOG and HumaLOG/HumuLIN are exactly the kind of one-character-different pairs that drive both harm severity and selection error), but a drug can sit on one list and not the other, and a policy that conflates them ends up either over-scoping the double-check burden or under-scoping the storage-separation requirement.

Turning ISMP’s list into your own list

The published LASA list is a menu, not a policy. Three steps turn it into something your organization can actually operate against.

1. Cross-reference against what you actually stock. A meaningful fraction of any published confused-names list will not be on your formulary at all. Adopting the full list unfiltered means maintaining storage-separation and double-check rules for drug pairs your pharmacy never dispenses — real administrative weight with no corresponding risk reduction. Run the list against your formulary and keep only the pairs where both members (or a plausible local substitute) are actually stocked.

2. Add pairs from your own event data. ISMP’s list is necessarily generic — it reflects error reports and name-pair analysis aggregated across many institutions, not your dispensing patterns, your ADC configuration, or your local brand contracts. Near-miss reports, medication-error reports, and ADC override logs are where local pairs surface that a national list would never catch: two look-alike products from the same manufacturer added to formulary in the same quarter, a compounded or repackaged product whose label resembles an unrelated stock item, or a pair that only collides because of how your specific shelving or bin layout places them next to each other. Medication use evaluation data and adverse event review are both legitimate feed sources for this, alongside a dedicated LASA-specific reporting channel if your event-reporting system supports tagging by contributing factor.

3. Review and reissue the list at a fixed cadence, not just when an event forces it. Formulary changes (new drugs, discontinued products, generic-to-brand or brand-to-generic switches, a wholesaler substitution during a shortage) all change which pairs are actually live risks. An annual review, timed to your P&T committee’s formulary review cycle so LASA status is checked as part of every addition rather than as a separate parallel process, keeps the list from drifting out of sync with what is actually on the shelf. Retire pairs where one member is discontinued or no longer stocked — carrying dead entries dilutes attention on the ones that still matter, the same failure the tall man lettering page documents for the FDA list’s discontinued names.

Storage and labeling separation

Once a pair is confirmed live on your list, the first mitigation to apply is physical, not technological: keep the two products from sitting next to each other anywhere a person picks one by hand.

Where the pair could collide	Separation strategy
Pharmacy shelving	Break strict alphabetical order for confirmed LASA pairs; shelve one member in a different aisle or section rather than adjacent
Automated dispensing cabinet (ADC) pockets	Assign non-adjacent pocket locations; where the ADC supports it, require an override or secondary confirmation to pull either member
Unit-dose and bin storage on the nursing unit	Physically separate bins, not just separate labels within the same bin; add an auxiliary LASA warning label distinct from the standard label
Compounding and repackaging areas	Stage one product at a time; do not pull both members of a pair to the workspace simultaneously
Refrigerated storage	Apply the same non-adjacent rule inside the fridge/freezer, which is easy to overlook because it is usually a smaller, denser space

Storage separation is worth doing first because it is cheap, does not depend on any system vendor’s configuration options, and closes off the failure mode where a person reaches for the wrong item without ever consulting a screen or label at all — a selection error that happens purely by spatial habit, which no amount of on-screen tall man lettering or CPOE alerting will catch.

Order-entry and technology safeguards

The second layer sits in the systems between the order and the hand that administers it. None of these is sufficient alone; each closes a different point in the chain.

• Require the indication on the order. Stating the purpose of the medication on the prescription or order — a practice ISMP recommends specifically for confusable names — gives every downstream reader a second signal beyond the drug name itself. A LASA pair rarely shares an indication, so “for hypertension” versus “for seizure prophylaxis” resolves an ambiguous name pair a human reading quickly might otherwise miss.
• Prevent consecutive listing on selection screens. Where the EHR or ADC software supports it, configure order sets and pick lists so that known LASA pairs do not appear next to each other alphabetically in a dropdown — the same adjacency risk as physical shelving, reproduced digitally.
• Enforce a minimum search-string length. A three- or four-character search on a shared prefix returns exactly the ambiguous set a LASA control exists to prevent; ISMP recommends configuring product search to require a minimum of the first five letters of a drug name.
• Barcode scanning at dispensing and administration. A barcode match against the active order is a positive-identification check that does not depend on a human correctly reading a name under time pressure — it catches a wrong-product selection regardless of whether the name was formatted, labeled, or double-checked correctly upstream.
• Smart infusion pump drug libraries. For LASA pairs that are also high-alert infusions, confirm the pump library entry itself is unambiguous (full name, no truncation, correct concentration default) rather than assuming the EHR order and the pump library were built from the same source data.

Test these controls the way you would test tall man lettering rendering: on the live screen or a real printed sample, not against a specification document. A pick-list adjacency rule that was configured correctly at go-live can silently stop working after a vendor content update rebuilds the order-set list from source data.

Independent double-checks: the strategy most often applied wrong

An independent double-check is not a second person glancing at what the first person already prepared. To function as intended, each checker has to arrive at their own conclusion from the original order before comparing notes — checker two verifies the patient, drug, dose, and route against the order independently, without seeing checker one’s calculation, selection, or stated result first. A check performed by looking over someone’s shoulder at what they already drew up, or by asking “does this look right to you,” is a confirmation-seeking exercise, not an independent check, and it inherits the first person’s error at roughly the same rate a single check would.

Two practical failure modes recur:

• Social pressure collapses independence. When the same two people check each other routinely, or when one is senior to the other, the second check tends toward confirming rather than genuinely re-deriving — especially under time pressure. The workflow has to structurally separate the two checks (each checker working from the original order, not from the other checker’s output) for the safeguard to do what it claims.
• Over-application degrades vigilance. Requiring an independent double-check on every medication, or on every LASA-listed pair regardless of actual risk, produces the same fatigue dynamic as an alarm sounding too often: checkers learn to move quickly through a check that is rarely where the real error turns up, and vigilance drops exactly where a genuinely high-risk pair needs it most. Reserve the independent double-check for the subset of your LASA list that is also high-alert, or where local event data shows a real near-miss history — not the full list uniformly.

Independent double-checks and barcode scanning are complementary, not redundant: a barcode scan verifies that the physical product in hand matches the order, but it cannot catch an error already built into the order itself (wrong drug prescribed for the intended indication, wrong dose calculated). A double-check on the order, done independently, is what catches that class of error. Neither substitutes for the other on a genuinely high-risk pair.

Where tall man lettering fits in the stack

Tall man lettering is the layer that acts at the moment of visual selection — a pharmacy or prescriber screen, a shelf label, a pump library entry — by making two similar names look less alike to a reader who already knows the convention. It is cheap, endorsed by ISMP, FDA, and The Joint Commission, and worth applying to every pair on your list that has a published tall man form. It is also, on its own, the weakest-evidenced layer in this stack: the experimental literature on whether it measurably reduces real clinical errors is mixed, and it depends entirely on every downstream system rendering it correctly, which multiple surveyed institutions report their own systems fail to do. Treat it as one input among the storage, order-entry, and double-check strategies above, not as the LASA program. Full detail — the FDA and ISMP list structures, the CD3 capitalization rule, per-surface verification, and the evidence review — is in the dedicated tall man lettering guide.

Accreditation expectations

US hospital accreditors treat LASA risk as a standing requirement, distinct from any single named safety goal: an accredited organization is expected to identify, from its own dispensing and event data, the look-alike/sound-alike medications it actually stocks, and to implement risk-reduction strategies for each pair on that list, reviewed on a recurring basis. The specific standard and element-of-performance numbering this sits under is accreditor-specific and gets renumbered periodically as standards manuals are revised — confirm the current citation against your accreditor’s published manual before referencing a fixed code in an internal policy document, rather than treating any single number as permanent. See National Patient Safety Goals for how the broader Goals program is structured and where a specific typographic tactic like tall man lettering is recommended rather than mandated.

Building the policy

A LASA program that survives a survey and a formulary change names five things:

1. The source list and version. The ISMP List of Confused Drug Names, with the retrieval date, since it is revised periodically.
2. Local filtering and additions. Which published pairs were removed because they are not stocked, and which local pairs were added from event data, with the rationale and date for each addition.
3. The mitigation assigned per pair. Not every pair needs every strategy — record which of storage separation, order-entry controls, tall man lettering, and independent double-check applies to each entry, and why.
4. The review cadence. Tied to the P&T committee’s formulary review cycle, with a defined annual full-list review regardless of whether any single change has triggered it.
5. The event-to-list feedback loop. How a near-miss or ADE involving a name-pair confusion gets routed back into a candidate addition to the list, not just closed as an isolated incident.

When a LASA selection error does reach a patient, the resulting review runs through the same machinery as any other adverse event: classification of individual versus system contribution via a just culture algorithm, escalation under sentinel event definitions where the harm threshold is met, and protection of the analysis itself under patient safety organization work-product privilege. A finding that a known LASA pair was stored adjacently, or that an independent double-check was performed as a shoulder-glance rather than an independent verification, is a system finding and belongs in the system column, not the individual one. For the broader improvement-cycle mechanics of running this kind of review, see the PDSA cycle and Model for Improvement and how a PIP write-up is assembled; practitioners formalizing this work often pursue CPPS certification. For the broader programme this sits inside, see the patient safety hub.

Frequently asked questions

Is the LASA list the same as the high-alert medications list?

No. High-alert status is about the severity of harm if an error occurs with a drug, independent of its name — insulin, opioids, anticoagulants, and concentrated electrolytes are the classic examples. LASA status is about name confusability specifically. The two lists overlap in places, since some high-alert drugs also have confusable names, but a drug can appear on one list and not the other, and a program should keep them as separate documents with separate criteria rather than merging them.

Where do we get the actual ISMP LASA list?

Directly from ISMP through ECRI’s ISMP resources site, which now hosts the ISMP List of Confused Drug Names (legacy ismp.org links redirect there). It requires registration to download. Do not rely on a third-party reproduction, and check the version date each time you pull it, since ISMP revises the list periodically.

How is a LASA list different from adopting tall man lettering?

Tall man lettering is one specific mitigation — a typographic convention applied to a subset of name pairs that have a published mixed-case form. The LASA list is broader: it is every confusable name pair your institution has identified as a real local risk, most of which need storage separation, order-entry controls, or an independent double-check regardless of whether a tall man form exists for that pair at all.

Which LASA pairs need an independent double-check, versus just storage separation?

Reserve the independent double-check for pairs that are also high-alert, or that carry a documented local near-miss or event history — applying it uniformly across every LASA-listed pair tends to degrade vigilance rather than improve it. Storage separation and order-entry controls are lower-cost and reasonable to apply across the full list.

How often should the list be reviewed?

At least annually, and structurally tied to your P&T committee’s formulary review cycle so that every new formulary addition is checked for LASA risk as part of the same process, rather than as a separate review that can drift out of sync with what is actually on the shelf.

Primary sources

• Institute for Safe Medication Practices, ISMP List of Confused Drug Names (LASA list), hosted by ECRI.
• US Food and Drug Administration, FDA Name Differentiation Project.
• Institute for Safe Medication Practices, FDA and ISMP Lists of Look-Alike Drug Names with Recommended Tall Man (Mixed Case) Letters.