No products in the cart.
MODULE 37: LOOK-ALIKE / SOUND-ALIKE (LASA) & HIGH-ALERT DRUG SAFETY
Section 37.3: The “Tall-Man Lettering” System Explained
A deep dive into the science and application of one of the most effective visual safeguards. We’ll review the ISMP-recommended list and discuss how to apply it consistently in labeling and electronic systems.
SECTION 37.3
The “Tall-Man Lettering” System Explained
Using Typography as a Cognitive Safety Tool.
37.3.1 The “Why”: Hacking the Brain’s Autopilot
We have established that many Look-Alike/Sound-Alike errors are not knowledge deficits but are caused by cognitive shortcuts and automaticity. Our brains are wired for efficiency; they excel at pattern recognition, often filling in the blanks based on the first and last few letters of a word without meticulously reading the middle. Tall-Man Lettering is a simple, elegant, and evidence-based strategy designed to “hack” this cognitive autopilot. It is a form of typographical highlighting that uses a mix of lower- and upper-case letters to draw attention to the dissimilarities in confusing drug names.
By capitalizing the parts of the names that are different (e.g., hydr**ALAZINE** vs. hydr**OXY**zine), Tall-Man lettering acts as a visual “speed bump.” It breaks the brain’s automatic reading process, forcing a momentary pause and a more conscious, deliberate analysis of the word. This brief interruption is often all that is needed to break the spell of confirmation bias and prevent a practitioner from picking the wrong drug. The Institute for Safe Medication Practices (ISMP) and the FDA have studied and promoted this technique for years because it is a low-cost, high-impact intervention that directly targets the root cognitive cause of many LASA errors. As a pharmacist, mastering the application of Tall-Man lettering is a core competency in medication safety, transforming you from a passive verifier into an active designer of a safer visual environment.
Retail Analogy: The Highlighter in the Textbook
Think back to studying for a major exam in pharmacy school. You’re reading a dense chapter on diuretics, and the text mentions two drugs with similar names but opposite effects on potassium levels. To ensure you don’t mix them up on the exam, you take out a bright yellow highlighter. You don’t highlight the whole name of each drug; that would be useless. Instead, you strategically highlight only the part of the name or the specific potassium-sparing or potassium-wasting property. For example:
“Triamterene is a potassium-SPARING diuretic, whereas hydrochlorothiazide is a potassium-WASTING diuretic.”
That small act of highlighting transforms the text. Now, every time you scan the page, your eyes are immediately drawn to that critical point of differentiation. You’ve created a visual flag that forces your brain to pay attention to the single most important difference. Tall-Man lettering is the professional, standardized version of this exact study habit, applied across the entire health system to prevent life-threatening exam failures in the real world.
37.3.2 The Science of Why It Works: Pre-Attentive Processing
Tall-Man lettering is effective because it leverages a cognitive phenomenon known as pre-attentive processing. This is our brain’s ability to subconsciously and very rapidly process certain basic visual features in our environment—like color, shape, size, and contrast—before we even devote conscious attention to them. When you see a single red letter in a sea of black letters, you don’t have to consciously search for it; it simply “pops out.”
Standard drug names, like ‘hydralazine’ and ‘hydroxyzine’, are visually monotonous. They are strings of similar-looking lowercase letters. When a busy practitioner glances at them, their pre-attentive brain sees “starts with ‘hydra’, ends with ‘zine'” and signals a match. Tall-Man lettering disrupts this monotony. By introducing uppercase letters into the middle of the word, it creates a unique visual signature:
- hydrALAZINE
- hydrOXYzine
Now, the pre-attentive brain no longer sees two identical patterns. It sees two distinct visual shapes. The block of capital letters “pops out,” forcing the conscious brain to engage and ask, “Why is this different?” This engagement triggers a more careful, letter-by-letter reading of the word, which is the critical step in catching a LASA error. Studies have shown that the use of Tall-Man lettering can significantly reduce selection errors from lists of confusing drug names, proving it is a powerful tool rooted in cognitive science.
The Goldilocks Principle: Why Consistency is Key
The effectiveness of Tall-Man lettering depends on its consistent and judicious application. If we capitalize letters randomly, or if every drug name has capital letters, the system breaks down. It would be like highlighting every single word in a textbook—the highlighting becomes meaningless noise. This is why it is critical to adhere to the standardized list of LASA pairs developed by ISMP and the FDA. These pairs have been selected based on actual error reports and are proven to be sources of confusion. By using only the approved list, we ensure that Tall-Man lettering remains a strong, clear, and effective signal for the most dangerous risks.
37.3.3 Masterclass Table: ISMP’s Official List of Tall-Man Letter Pairs
This table details the official list of Look-Alike Drug Name Pairs with Recommended Tall-Man Letters, endorsed by both the ISMP and the FDA. As a hospital pharmacist, your goal is to ensure these are implemented consistently across all platforms in your institution.
| Recommended Tall-Man Name | Confused Name | Primary Risk of Mix-Up | Pharmacist’s Implementation Focus |
|---|---|---|---|
| acetaZOLAMIDE | acetoHEXAMIDE | Giving the diuretic for diabetes (or vice-versa) can lead to severe hypoglycemia or untreated glaucoma/edema. | Focus on ADC screens and pharmacy shelf labels where these oral solids might be stored. |
| buPROPion | busPIRone | Swapping the antidepressant for the anxiolytic can lead to worsening anxiety, untreated depression, and risk of seizures (especially with bupropion). | A classic oral medication pair. Critical for CPOE, e-prescribing picklists, and ADC display. |
| chlorproMAZINE | chlorproPAMIDE | Giving the antipsychotic instead of the oral hypoglycemic can result in severe, refractory hypoglycemia and neurological side effects. | Critical for labels in long-term care settings and hospital formularies. Check for both on admission med rec. |
| clomiPHENE | clomiPRAMINE | Giving the tricyclic antidepressant instead of the fertility drug can lead to anticholinergic toxicity and failure of fertility treatment. | Important for outpatient and specialty pharmacy systems, but can appear on hospital admission. |
| cycloSERINE | cycloSPORINE | Giving the potent immunosuppressant instead of the second-line tuberculosis agent can lead to life-threatening infections and renal toxicity. | Ensure segregation in the pharmacy. This is a high-risk, low-frequency error that systems must prevent. |
| DAUNOrubicin | DOXOrubicin | While both are anthracycline chemotherapy agents, they have different indications and cumulative cardiotoxicity limits. A swap can lead to improper treatment and overdose. | Absolute must for any oncology pharmacy information system, CPOE, and chemo prep software. |
| DOBUTamine | DOPamine | Giving dopamine (a potent pressor with variable effects) instead of dobutamine (primarily an inotrope) can cause excessive vasoconstriction and arrhythmias. | Critical for all smart pump libraries, ADC screens in the ICU/ED, and pre-printed code blue forms. |
| glipiZIDE | glyBURIDE | While both are sulfonylureas, glyburide has a much longer half-life and carries a higher risk of prolonged hypoglycemia, especially in the elderly and renally impaired. | Key for admission medication reconciliation and CPOE to guide prescribers to the safer, formulary agent (often glipizide). |
| hydrALAZINE | hydrOXYzine | Giving the antihistamine/anxiolytic (hydroxyzine) for a hypertensive crisis will have no effect on blood pressure, leading to end-organ damage. Giving the vasodilator (hydralazine) for anxiety can cause severe hypotension. | This is a foundational LASA pair. Must be applied everywhere: ADCs, pharmacy shelves, CPOE, MARs. |
| HYDROmorphone | Morphine | Hydromorphone is 5-7 times more potent. A mg-for-mg swap is a potentially fatal overdose causing respiratory arrest. | Top priority for all systems. Must have Tall-Man lettering, High-Alert labels, and physical segregation in all ADCs and pharmacy storage areas. |
| medroxyPROGESTERone | methylPREDNISolone methylTESTOSTERone | Swapping the hormone (progesterone) for the steroid or testosterone can lead to complete failure of therapy and significant hormonal side effects. | Check CPOE and pharmacy labels. Pay close attention to Depo-Provera vs. Depo-Medrol vs. Depo-Testosterone. |
| mitoXANTRONE | DAUNOrubicin DOXOrubicin | All are chemo agents, but mitoxantrone has a distinct mechanism and toxicity profile. A swap leads to ineffective cancer treatment and unexpected toxicities. | Essential for all oncology systems. Segregation in the chemo pharmacy is critical. |
| niCARdipine | NIFEdipine | While both are CCBs, nicardipine is a continuous IV infusion for hypertensive emergencies, while nifedipine is an oral agent. Swapping them is a major wrong-route/wrong-drug error. | Focus on CPOE to prevent ordering the wrong formulation. Separation in the pharmacy is key. |
| predniSONE | prednisoLONE | Prednisone is a prodrug that must be converted by the liver to the active prednisolone. In patients with severe liver failure, prednisone may be ineffective. | A clinical nuance. CPOE alerts can be built to flag prednisone use in patients with high LFTs and suggest switching to prednisolone. |
| SOLu-CORTEF | SOLu-MEDROL | Both are injectable steroids, but have different potencies. (Hydrocortisone vs. Methylprednisolone). A swap can lead to under- or over-dosing of steroid effect. | These look-alike boxes are a classic shelf error. Use Tall-Man shelf labels and separate them physically in the pharmacy and ADCs. |
| sulfaDIAZINE | sulfaSALAZINE | Sulfadiazine is an antibiotic, while sulfasalazine is used for inflammatory bowel disease. A swap leads to treatment failure. | Important for pharmacy shelf labeling and CPOE picklists. |
| TOLAZamide | TOLBUTamide | Both are first-generation sulfonylureas. Tolbutamide has a shorter duration of action. A mix-up could lead to unpredictable glycemic control. | Mostly a legacy issue, but important to check during med rec for older patients. |
| vinBLAStine | vinCRIStine | A classic chemo pair. Vinblastine is often dosed in tens of mg; vincristine is capped at 2 mg. An overdose of either is fatal. Vincristine given intrathecally is fatal. | Absolute top priority for all oncology systems, labeling, and storage. Must be segregated. Dispense vincristine in a minibag only. |
37.3.4 Implementation: From Policy to Practice
Recognizing the need for Tall-Man lettering is easy; implementing it consistently across a complex health system is a significant operational challenge that requires a pharmacist’s leadership. It must be applied in every location where a drug name appears to be effective.
Your Implementation Playbook
| System | Action Plan |
|---|---|
| 1. Pharmacy Information System & CPOE (e.g., Epic, Cerner) |
This is the source of truth. Work with the pharmacy informatics team to change the “display name” for all drugs on the ISMP list. This change will then cascade down to most other electronic systems, including the MAR and CPOE picklists. This is the highest-yield intervention. |
| 2. Automated Dispensing Cabinets (ADCs) (e.g., Pyxis, Omnicell) |
The ADC database is often separate from the main hospital EHR. You must work with the team that manages the ADC formulary to manually edit the drug names to reflect Tall-Man lettering on the ADC screen. This is a critical step, as the ADC screen is the point of selection for the nurse. |
| 3. Physical Pharmacy Labels | Ensure that your pharmacy’s label-printing software is configured to use Tall-Man lettering. This applies to shelf labels for inventory, labels for compounded products, and labels for patient-specific dispensed items. Consistency is paramount. |
| 4. Smart Pump Drug Libraries | Collaborate with the teams managing your smart infusion pump libraries. The drug name displayed on the pump screen should match the Tall-Man convention used in all other systems to provide a final confirmation before infusion begins. |
Critical Pitfall: Do Not Create Your Own Tall-Man Names!
While it may be tempting to apply Tall-Man lettering to other drug pairs you find confusing, this practice is strongly discouraged by ISMP. Creating non-standard names can introduce new and unforeseen error pathways. For example, if one hospital capitalizes “levoFLOXacin” and another capitalizes “levofloxACIN,” it creates confusion for traveling nurses or providers who work at multiple sites. Stick to the nationally standardized, evidence-based list. If you identify a new, dangerous LASA pair at your institution, your role is to report it to ISMP for consideration, not to create a local, non-standard solution.
A Piece of a Larger Puzzle
Tall-Man lettering is an elegant and effective tool, but it is not a panacea. It is one layer of defense in a comprehensive medication safety strategy. It should always be used in combination with the other strategies discussed in this module, including auxiliary warning labels, strategic segregation, and robust independent double-check procedures. When a pharmacist successfully champions the consistent implementation of Tall-Man lettering across all hospital systems, they have done more for patient safety than could ever be achieved by simply telling their colleagues to “be more careful.” They have changed the system itself to make it safer.
