Which drugs are high-alert, and why are look-alike names dangerous?
PTCB topic: High-alert and look-alike/sound-alike drugs
- High-alert means an error causes serious harm, not that errors are common.
- Community list: insulin, opioids, warfarin, methotrexate for non-cancer use.
- Humulin R U-500 in a U-100 syringe can cause a 5-fold overdose.
- Methotrexate for rheumatoid arthritis is once weekly; daily is a red flag.
- LASA pairs like hydroxyzine and hydralazine have easily confused names.
Key facts
- ISMP defines high-alert medications by the harm an error causes, not by how often errors happen.
- ISMP's community list includes insulin, opioids, antithrombotics such as warfarin, oral chemotherapy, carbamazepine and methotrexate for non-cancer use.
- ISMP's acute-care list adds IV and concentrated products, such as potassium chloride for injection concentrate and insulin U-500 (special emphasis).
Show all 7 key factsShow fewer
- Humulin R U-500 has 5 times as much insulin per mL as U-100; measuring it in a U-100 syringe can cause a 5-fold overdose.
- Methotrexate for rheumatoid arthritis is dosed once weekly; taking the weekly dose every day has caused deaths.
- LASA pairs on ISMP's or FDA's lists include hydroxyzine/hydralazine, Celexa/Celebrex, HumaLOG/HumuLIN and metoprolol succinate/tartrate.
- Brintellix was renamed Trintellix in 2016 after confusion with Brilinta.
Quick check1 question · 2 more at the end
Which statement best describes a high-alert medication?
Correct answer: B.
ISMP defines high-alert medications by the harm an error can cause, not by how often errors happen: mistakes with them may or may not be more common, but the consequences are more severe. Examples on ISMP's lists include insulin, opioids, warfarin and oral methotrexate for non-cancer use. Pharmacies protect these drugs with extra safeguards such as auxiliary labels, automated alerts and double checks.
A ISMP says errors with high-alert drugs may or may not be more common, so error frequency is not the definition.
B Correct: a high-alert drug carries a heightened risk of significant patient harm when it is used in error.
C Prior authorization is an insurance billing step and has nothing to do with the high-alert label.
D Controlled-substance schedules reflect abuse potential; many high-alert drugs, such as insulin and warfarin, are not controlled.
Full lesson
Each part starts with its main idea. Open a part when you want the details.
The short answer: A high-alert medication is one that is more likely to cause serious harm when it is used in error, whether or not errors with it are more common. ISMP's lists include insulin, opioids, warfarin and other anticoagulants, and oral methotrexate for non-cancer use. Look-alike/sound-alike (LASA) drugs have names that are easily confused, such as hydroxyzine and hydralazine.
1 What makes a medication "high-alert"?A high-alert medication is one where a single mistake is likely to cause serious harm. 1 min
A high-alert medication is one where a single mistake is likely to cause serious harm. The Institute for Safe Medication Practices (ISMP) points out that errors with these drugs may or may not happen more often than with other drugs. What sets them apart is how bad the result is when an error does happen.
The 2026 PTCE outline lists high-alert/high-risk medications and look-alike/sound-alike (LASA) medications as one knowledge area. You need to recognize both groups and know why each one needs extra care.
2 Which drugs are on ISMP's high-alert lists?ISMP keeps separate high-alert lists for community and acute-care settings. 1 min
ISMP keeps separate high-alert lists for community and acute-care settings. A few drugs show up on both.
| Setting | Examples from ISMP's list |
|---|---|
| Community/ambulatory | Insulin (all forms, with U-500 singled out), opioids (all routes), oral sulfonylureas, chemotherapy, antithrombotics such as warfarin and heparin, carbamazepine, methotrexate for non-cancer use, pediatric liquids that need measuring |
| Acute care (hospital) | Insulin (subcutaneous and IV, with U-500 singled out), antithrombotics, opioids (all routes), IV sedation agents, potassium chloride for injection concentrate, hypertonic sodium chloride (above 0.9%), dextrose 20% or greater |
Pay attention to the exact wording. Sodium chloride counts only when it is hypertonic, and dextrose only at 20% or more. Plain 0.9% saline and dextrose 5% are not on the list.
3 Why are strength and schedule mix-ups so dangerous?The deadliest high-alert errors often involve the right drug given at a much higher dose. 1 min
The deadliest high-alert errors often involve the right drug given at a much higher dose. Three examples come up again and again:
- Concentrated insulin. Humulin R U-500 has 500 units per mL, 5 times as much as U-100. The label says to measure vial doses only with a U-500 syringe, because a U-100 syringe can give a 5-fold overdose.
- Weekly methotrexate. For rheumatoid arthritis, the label dose is once weekly. Patients who took the weekly dose every day have died, so directions that say "daily" are a red flag.
- Oral opioid concentrates. A concentrated solution holds more drug in each mL. If the wrong bottle is picked, the patient gets a much bigger dose from the same volume.
4 What are look-alike/sound-alike (LASA) drugs?LASA drugs have names that look or sound so much alike that people mix them up when reading, typing or hearing them. 1 min
LASA drugs have names that look or sound so much alike that people mix them up when reading, typing or hearing them. ISMP's List of Confused Drug Names and FDA's tall man list name pairs that have actually caused errors.
| Pair | Why it is risky |
|---|---|
| hydrOXYzine / hydrALAZINE | On FDA's tall man list; the names differ only in the middle |
| CeleXA / CeleBREX | Brand names that differ by only a few letters |
| glipiZIDE / glyBURIDE | Two sulfonylureas, both high-alert in hospitals |
| metoprolol succinate / tartrate | Same drug name, different salt and release form |
In rare cases a name gets changed. In 2016, Brintellix (vortioxetine) became Trintellix after reports of confusion with Brilinta (ticagrelor). The usual fixes are cheaper and work faster: tall man letters, storing the pair apart, and writing both names plus the purpose on the prescription.
5 What the technician doesThe technician's job is to notice the warning sign and stop the process before the error moves on. 1 min
The technician's job is to notice the warning sign and stop the process before the error moves on.
- Treat insulin, opioids, anticoagulants and methotrexate as drugs that always get a careful second look.
- Check the concentration and units on every high-alert product. Read the full label, and don't pick by bottle color or shelf spot.
- Hold the prescription for the pharmacist when a name could be read two ways or the directions don't fit the drug. Daily methotrexate is one example.
- Never rewrite directions or pick between two possible drugs yourself.
Common mistakes
The traps students fall into most. Read these before you practice.
Watch out: High-alert means high harm if an error occurs, not the most frequent errors.
Watch out: Same volume of a stronger concentration means a bigger dose, not the same dose.
Watch out: Methotrexate for rheumatoid arthritis is once weekly, not daily.
Watch out: An ambiguous drug name is clarified with the prescriber, not guessed from the patient's answer.
How to remember it
Two short phrases cover this whole topic, one for each drug group. For high-alert drugs, remember "harm, not how often." For LASA pairs, picture "two names, one bin, one wrong pick."
Self-check:
- In your own words, what makes a drug high-alert?
- Name three drugs on ISMP's community high-alert list.
- Explain why "methotrexate 2.5 mg, 4 tablets daily" for rheumatoid arthritis has to go to the pharmacist.