LASA Drugs: List, Examples & Safe Handling (2026 Guide)

Last reviewed: 21 October 2026

What are LASA drugs?

LASA stands for Look-Alike Sound-Alike. LASA drugs are medicines whose names are spelled or pronounced similarly, or whose packaging, labels or tablets look alike. That similarity makes them easy to confuse at every step, from writing a prescription to giving a dose.

Two simple examples:

• Sound-alike names: hydrALAZINE (for blood pressure) and hydrOXYzine (an antihistamine)
• Look-alike packs: two strengths of the same injection in near-identical vials

LASA mix-ups are one of the most common causes of medication errors worldwide. That is why the World Health Organization made them a focus of its Medication Without Harm challenge and published dedicated guidance in October 2023. The risk keeps growing as new brands and generics enter the market, many with names that differ by only a letter or two.

This guide explains why LASA errors happen, lists common LASA pairs, and sets out practical safeguards for hospitals, pharmacies and manufacturers.

Common Risk Factors

LASA errors rarely have a single cause. They happen when a similar name or pack meets a busy, distracted or incomplete process. The most common contributing factors are:

• Handwritten or abbreviated orders. Poor handwriting and abbreviations turn two different drugs into the same scribble.
• Verbal and telephone orders. Names such as clonazePAM and cloNIDine sound almost identical on a noisy ward.
• Unfamiliarity. New staff, locum cover, and newly launched brands or generics.
• Identical packaging. The same manufacturer’s “house style” applied to different products or strengths.
• Overlapping strengths, dosage forms and frequencies. Both drugs come as 10 mg tablets taken once daily, so nothing looks wrong.
• Similar clinical use. Both drugs are used on the same ward, so the error doesn’t stand out.
• Storage side by side. Alphabetical shelving places LASA pairs next to each other.
• Computer pick lists. Typing the first three letters in an e-prescribing or pharmacy system brings up both drugs.

LASA drugs list: common examples

The table below lists well-documented LASA pairs, shown in Tall Man lettering where ISMP or the FDA recommends it. Pairs marked High-alert involve at least one drug on ISMP’s high-alert list, where a mix-up is most likely to cause serious harm.

Free download: LASA Drugs Toolkit (PDF)

24 LASA pairs with Tall Man spellings, 24 printable warning labels and a hospital LASA list template.

Brand names matter too. In 2016 the FDA approved renaming the antidepressant Brintellix to Trintellix after it was repeatedly confused with the antiplatelet Brilinta. Every country also has its own local brand pairs, so a hospital’s LASA list should always include the brands it actually stocks.

For the full list, see the ISMP List of Confused Drug Names, updated in 2023 with more than 80 new pairs.

Look-alike packaging and strengths

Not all LASA errors involve names. Some of the most dangerous involve products that look the same:

• Different strengths of one drug in similar packs. Classic examples are heparin vials of different concentrations, and insulin pens with different strengths.
• Concentrated electrolytes beside ordinary infusions. Potassium chloride concentrate looks like other small vials but can be fatal if injected undiluted.
• One manufacturer’s house style. Different products get the same colours, layout and font, so only the small print differs.
• Similar ampoules and vials. Clear glass, white labels and tiny text make injections in emergency trolleys especially easy to mix up.
• Same-coloured tablets. Once taken out of the strip, many white round tablets look identical.

Packaging confusion is where hospitals and manufacturers must work together. Pharmacies should report look-alike packs to the supplier and to the national regulator. Manufacturers should treat such reports as quality complaints and act on them, as explained in the manufacturer’s section below.

Strategies To Avoid Errors

No single safeguard stops LASA errors. The safest systems add a check at every stage a medicine passes through, from purchase to the patient.

1. Procurement

• Keep the formulary lean. Stock as few strengths and brands of each drug as clinical needs allow.
• Before approving a new product or supplier, place the pack next to existing stock and look for confusion risks.
• When two suppliers’ packs look alike, choose the one that is easier to tell apart, even if it isn’t the cheapest.
• Ask the pharmacy and therapeutics committee to review the LASA list before every formulary change.

2. Storage

• Separate LASA pairs physically. Never shelve them side by side, even when alphabetical order would put them together.
• Use Tall Man lettering on shelf labels, bins and automated dispensing cabinet screens.
• Add a standard “LASA – check name and strength” warning sticker (a shelf talker) in the same style everywhere in the facility.
• Keep concentrated electrolytes and high-alert LASA drugs out of ward stock wherever possible.
• Review emergency trolleys and anaesthesia trays, where similar ampoules sit close together under time pressure. our guide to common antidotes lists the ones pharmacists most often need.

3. Prescribing

• Use electronic prescribing where available, with Tall Man lettering in drug pick lists.
• Write the generic name, strength, dosage form, dose, route and frequency, and avoid abbreviations.
• Include the indication (for example “for hypertension”). It is one of the simplest ways for a pharmacist or nurse to spot a LASA mix-up.
• Keep verbal and telephone orders for urgent situations. The receiver should write the order down, read it back and spell the drug name.

4. Dispensing

• Select medicines by reading the label, never by remembering where something sits on the shelf or what the pack looks like.
• Check the prescription, the product and the dispensing label against each other (a three-way check).
• Scan the barcode where the system allows it.
• Ask a second person to check independently for high-alert LASA drugs.
• When counselling, show the patient the medicine and confirm what it is for.

5. Administration

• Apply the “rights” of medication administration, especially right drug, right dose and right route, and read the label at the bedside.
• Use barcode scanning at the bedside where available.
• If a patient says a medicine looks different from usual, stop and check before giving it.

6. Patient Education

• Teach patients the generic and brand names of their medicines, and what each one is for.
• Tell them when a refill comes from a different manufacturer and will look different.
• Encourage patients and carers to speak up if a medicine looks, sounds or is named differently from what they expect.
• Give them an up-to-date written medication list.

7. Technology

• Barcode scanning at dispensing and administration catches errors that people miss.
• E-prescribing alerts can warn when a known LASA drug is chosen, or ask for the indication.
• Pick lists that require more letters before showing results reduce wrong-drug selection.
• Technology supports people’s checks; it doesn’t replace them.

8. Reporting and Learning

• Report every LASA error and near miss through your incident system, and make near misses as easy to report as actual errors. If an error reaches and harms a patient, report it to your national pharmacovigilance centre as well. Our guide to adverse drug reactions covers the basics.
• Review reports regularly, add new pairs to the LASA list, and share lessons with staff.
• Treat repeated LASA errors as a system problem, with a root-cause analysis and a CAPA, rather than blaming individuals. See our guide to CAPA with examples.

Layers of defence against LASA errors

LASA layers of defence · 6 stages from purchase to patient

Tall Man lettering explained

Tall Man lettering writes the part of a drug name that tells it apart from a similar name in CAPITALS, for example metFORMIN and metroNIDAZOLE, or hydrALAZINE and hydrOXYzine. It draws the eye to the letters that matter.

• Who sets it: the US FDA publishes a list of established names with Tall Man letters, and ISMP publishes an additional list. Many countries and hospitals adopt these lists and add their own local pairs.
• Where to use it: shelf and bin labels, automated dispensing cabinets, e-prescribing and pharmacy systems, dispensing labels, and LASA warning stickers.
• Be consistent: use the same spelling everywhere in the facility, because mixed styles create confusion of their own.
• Know its limits: research shows Tall Man lettering has only a modest effect on its own. Use it as one layer among several, alongside separate storage, barcode scanning and indication-based prescribing, not as the whole solution.

How to build and maintain a hospital LASA list

Accreditation bodies such as The Joint Commission and JCI expect hospitals to know their own LASA risks and act on them. A practical process looks like this:

1. Assign ownership. The pharmacy and therapeutics (or medication safety) committee owns the list, and a named pharmacist keeps it up to date.
2. Start from published lists. Use the ISMP List of Confused Drug Names and the FDA and ISMP Tall Man lists, then keep only the drugs your hospital actually stocks.
3. Add local evidence. Include pairs from your own incident and near-miss reports, local brand names, and look-alike packs from your current suppliers.
4. Decide the controls for each pair. For example: separate storage, a shelf warning, Tall Man spelling in the system, a barcode check, or a double check for high-alert drugs.
5. Communicate it. Display the list in the pharmacy and on wards, include it in staff induction, and build it into the e-prescribing and pharmacy systems.
6. Review it regularly. At least once a year, and whenever a new product, brand or supplier is added.

The role of regulators and safety organisations

• FDA: reviews proposed brand names before approval to screen out confusing names, can ask manufacturers to change labels or names (as with Brintellix and Trintellix), and publishes the Tall Man list.
• ISMP: collects error reports, publishes the List of Confused Drug Names and its Tall Man list, and issues safety alerts.
• WHO: published Medication safety for look-alike, sound-alike medicines in 2023 as part of its Medication Without Harm challenge, giving strategies for both organisations and healthcare workers.
• National regulators: in Pakistan this is DRAP. National regulators approve product names and labels, and receive reports of medication errors and product problems through their pharmacovigilance systems.

Challenges that remain

• Thousands of brands and generics, with new names launched every year.
• Unclear handwriting and verbal orders still common in many settings.
• Limited access to barcode scanning and e-prescribing in smaller hospitals and pharmacies.
• Under-reporting of near misses, which hides the pairs that matter most.

A manufacturer’s view: preventing look-alike packs at source

Most LASA guidance is written for hospitals. Many look-alike problems, though, start much earlier: at the manufacturer. From a pharmaceutical quality perspective, these controls prevent confusion before a product ever reaches a pharmacy shelf:

• Artwork design review. New or changed labels and cartons should be checked against the company’s other products and against competitors’ products in the same therapeutic area. Use different colours, layouts and type sizes for different strengths, and make the drug name and strength the most prominent elements.
• Change control. Any change to artwork, pack colour or the packaging supplier goes through formal change control, with a documented LASA risk assessment.
• Line clearance. Before packaging begins, the line is cleared of all previous product, labels and printed materials. This prevents mixed packs, a direct cause of wrong-drug errors.
• Printed packaging material control. Store and issue printed materials securely, reconcile them carefully, and use code readers or vision systems on the line to verify each pack.
• Complaint handling and CAPA. When a hospital or pharmacy reports two packs as confusing, treat it as a quality complaint. Investigate it, assess the risk, and correct the artwork where needed.

A LASA safety culture works best when pharmacists in hospitals and quality professionals in industry share what they see.

Medication safety is a core topic in pharmacist licensing exams. If you are preparing for one, see our FPGEE guide and our tips on passing the NAPLEX first time.

Frequently asked questions

References

• WHO – Medication safety for look-alike, sound-alike medicines (2023)
• ISMP – List of Confused Drug Names
• ISMP – Updated List of Confused Drug Names (July 2023)
• Ministry of Health Malaysia – Guide on Handling Look Alike, Sound Alike Medications (2012)
• The Joint Commission – Look-alike/sound-alike medications resources

This guide is for educational purposes. Always follow your hospital’s policies and current national guidance.