Practitioners' Reporting News

Tips for Using USP's Similar Names List

Issued August 31, 2004

In April 2004, USP released its updated resource of similar drug names. In addition to meeting the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) National Patient Safety Goals, this resource can also be used by healthcare settings other than hospitals to meet patient safety efforts. At first glance, this extensive list might appear daunting and one might question how best to use this resource in their practice. For this reason, USP's Center for the Advancement of Patient Safety (CAPS) has developed some tips to help practitioners use this resource efficiently:

  • Evaluate your facility's existing formulary and identify which products appear on USP's similar names list. Perhaps a good place to start is to review your most severe errors and the drugs involved in those errors.
  • If you are considering adding a product to your formulary, use USP's list to determine if there could be a potential look-alike/sound-alike problem with that product and others on your formulary.
  • Use the list to determine if products with similar names are stocked next to one another in the pharmacy and any area where medications are stored. If so, physically separate these products or employ some other method to distinguish them from one another (i.e., use colored dividers to separate the products on the shelves; apply brightly colored stickers alerting staff to the potential for similarity, etc.).
  • Track medication errors caused by look-alike/sound-alike drug names and identify the products most frequently involved. Create ways to alert staff to the mix up's, such as posting the information in a newsletter.
  • Utilize Tall Man letters to distinguish the product's appearance. This technique works especially well on the manufacturer's packaging, but can also be implemented in pharmacy software and labeling. Prescribers might consider this technique when writing orders or prescriptions.
  • Implement policies that prohibit verbal orders for products that sound alike, especially those already mixed up at your facility.
  • Perform a Failure Modes and Effects Analysis, especially for mix up's that can result in harmful or fatal outcomes.

To further assist in this effort, USP has reviewed reports submitted to its two medication error reporting databases—MEDMARX® and the USP Medication Errors Reporting Program—and has identified those products which have been reported as being associated with harm. Data was queried from MEDMARX for calendar year's 2000-2003 and from MER from inception through April 2004. In addition, USP identified which of those similar drug name pairs also had similar labeling/packaging reported as a problem. These findings are displayed below.

Table displays the most frequent drug name pairs for Categories* F, G, H, and I, with the most severe Category noted.

Most Frequent Similar Drug Name Pairs for Categories* F, G, H, and I Pair Appears in Both MER & MEDMARX Similar Labeling/Packaging also Reported as a Cause of Error Most Severe Category* Reported
Amiodarone vs. Amrinone (Former nomenclature for Inamrinone)†     I
Amphotericin B vs. Amphotericin B, Lipid Complex X   I
Amaryl vs. Reminyl X   H
Chlorpromazine vs. Chlorpropamide X   G
Clozaril vs. Colazal     F
Diazepam vs. Lorazepam X   H
Doxorubicin vs. Doxorubicin, Liposomal   X I
Fentanyl vs. Sufentanil     H
Lamictal vs. Lamisil     H
Navane vs. Norvasc     F
Opium, Camphorated vs. Opium Tincture, Deodorized     I
Pitocin vs. Pitressin X X I
Prednisone vs. Primidone     F
Quinidine vs. Quinine     H
Seroquel vs. Serzone     F
* The National Coordinating Council for Medication Error Reporting and Prevention's Error Category Index may be found at http://www.nccmerp.org/medErrorCatIndex.

† Amrinone's name was changed to Inamrinone.

The list below displays drug name pairs where a single report was submitted and resulted in a fatal outcome.

  • Bretylium vs. Brevibloc
  • Diflucan vs. Diprivan
  • Isordil vs. Plendil
  • Primacor vs. Primaxin
  • Taxol vs. Taxotere

In addition, JCAHO has released a list of similar names which institutions must select from.

Similar drug name issues should be reported to USP's medication error reporting programs so that this valuable resource can be updated and used by healthcare professionals. For information on how to report errors, visit http://www.usp.org/hqi/patientSafety, email , or call
1-800-23-ERROR (1-800-233-7767).


Readers are advised that official USP cautions and warnings for drugs appear in the USP–NF or USP DI. Unless otherwise indicated, any advice or opinions expressed herein reflect solely the judgment of USP staff. Such statements are intended for further consideration and evaluation and may or may not be applicable to a particular practice. The USP Medication Errors Reporting Program is presented in cooperation with the Institute for Safe Medication Practices.