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FDA Public Health Advisory
January 2006
Consumers Filling U.S. Prescriptions Abroad May Get the Wrong Active Ingredient Because of Confusing Drug Names

The U.S Food and Drug Administration (FDA) is advising healthcare professionals and consumers that filling U.S. prescriptions abroad may give patients the wrong active ingredient for treating their health condition. Some FDA-approved products have the same brand names as drug products that are marketed outside the U.S. but contain completely different active ingredients. In addition, 105 U.S. brand names are so similar to foreign brand names used for products with different active ingredients that patients who fill prescriptions abroad may inadvertently get the wrong drugs. Using the wrong drugs creates avoidable risks of adverse drug reactions with no health improvements. Consumers who fill U.S. prescriptions abroad, either when traveling or when shopping at foreign internet pharmacies, need to take caution because foreign drugs may use identical or potentially confusing brand names for products with different active ingredients.

Identical or very similar brand names, if associated with different active ingredients, may cause preventable pharmacy errors because approximately three quarters of all U.S. prescriptions are written using brand names rather than the scientific (or so-called "generic") names of the active ingredients.¹ To minimize confusion within the U.S., FDA has procedures in place to review brand names for use in the U.S. proposed by the manufacturer, relative to U.S. marketed product names. No international regulatory system exists, however, to ensure that new brand names are sufficiently different from existing ones elsewhere in the world to prevent undue confusion by pharmacists who are filling prescriptions from outside their country.

The FDA found 18 foreign drug products that use the same brand name as an FDA-approved medication but contain a different active ingredient. Table 1 lists the 18 foreign brand names, along with the active ingredients used in the U.S. and abroad, and the foreign country where the other active ingredient is marketed. The list excludes drug products available only in a hospital setting and drugs regulated as controlled substances in the U.S. This list focuses on prescription-only products, although similar and identical names exist among over-the-counter remedies.² While some of the identical brand names have different active ingredients appropriate for the same health condition, these products should not be substituted without the guidance of a healthcare professional due to different doses, side effects, allergies, and interactions with other drugs.

FDA cautions that this list of identical brand names used for different drugs in other countries is probably not comprehensive and is subject to change. To develop this list, FDA used Chemindex(TM), a proprietary database from a data vendor named IMS Health to compare brand names for single-ingredient products marketed in the U.S. and 28 other industrialized countries in 2003.³ FDA also used Martindale Product Index, an online drug reference database to identify some foreign drug names and indications.

Earlier reports confirm the risks described here. In a January 13, 2005 newsletter, the Institute for Safe Medication Practices (ISMP) described a serious adverse event resulting from drug marketed abroad that had the same name as a product marketed in the U.S. but contained an active ingredient different from the product in the U.S. ISMP described a patient who traveled to Serbia and ran out of Dilacor XR (diltiazem extended release), marketed by Watson Labs in the U.S., and used to treat high blood pressure. A Serbian pharmacist filled the prescription with digoxin 0.25 mg because in Serbia, Dilacor, marketed by a local company, is a brand name for digoxin. Digoxin is used to treat heart failure as well as abnormal heart rhythms, and requires blood testing for close monitoring of the amount of the drug in the body to avoid serious adverse events. The patient, who continued taking the medication without realizing it was digoxin and not diltiazem, was hospitalized with life-threatening drug toxicity after his return to the U.S. An article in the Wall Street Journal on August 16, 2005 noted the risks inherent in identical brand names being used for products with different active ingredients and listed six such brand names for drugs sold in the both U.S. and in Europe. ⁴

FDA has also found 105 U.S. brand names for which there are foreign brand names that look or sound so much alike that consumers who fill prescriptions abroad may receive the wrong active ingredient as the result of pharmacy errors.⁵ For example, Ambyen is a brand name for amiodarone, used to treat abnormal heart rhythms, in the United Kingdom. A supply of Amyben in place of Ambien (zolpidem tartrate), a sleeping medicine marketed in the U.S., could have a serious adverse outcome. These very similar sounding brand names and the associated active ingredients are listed in Table 2 below, though this list is likely incomplete.

The similarities between the U.S. and foreign names listed in Table 2 may contribute to potentially harmful pharmacy errors. Using a computer algorithm, FDA compared the degree of similarity of drug names listed in Table 2 with the degree of similarity of drug names that ISMP reported were actually confused by pharmacists and doctors in the U.S.⁶ The drug name pairs in Table 2 are much more similar than those for which ISMP has reported that a patient received the wrong drug because of drug name confusion. This advisory complements the ISMP study data findings. FDA plans to update this advisory, as appropriate, after it collects more information.

*These products have different dosage forms, so that use of the wrong drug seems relatively unlikely, although the difference in active ingredients should be noted.
**Naqua was identified based on the Wall Street Journal story on August 6, 2005.

Footnotes:

1 Verispan LLC, Vector One (TM) National, Years Q3/2005, Data Extracted 11-2005. FDA believes that use of brand names in writing prescription is higher for drugs for which no generic is available and lower for drugs commonly sold as generic products.

2 One example is the insomnia treatment Sominex, an over-the-counter medication, which has diphenhydramine as the active ingredient in the U.S. and promethazine as the active ingredient in the U.K.

3 IMS Health, IMS Chemindex(TM) 2003 For additional information see http://www.imshealth.com/web/product/0,3155,64576068_63872702_70297674_71263626.00.html

4 One drug from the list published in the Wall Street Journal, Sominex, was not included because it is available over-the-counter in the U.S.

5 To compile this list of look-alike or sound-alike names, FDA used IMS' Chemindex and a phonetic-coding algorithm to rank pairs of drug names by their similarity. FDA then refined the list by removing any potentially confusing foreign products that also had an identical U.S. counterpart (same brand name, same active ingredient). FDA also deleted any products that FDA pharmacists determined were invalid or inappropriate (e.g., brand names like "Pain Reliever" or "Decongestant" and some dietary supplements).  FDA then identified those products for which the brand names were so similar that FDA would have asked for more information about the foreign name before approving it for use in the U.S.

6 See http://www.ismp.org/Tools/confuseddrugnames.pdf

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