FDA Warns of Name Confusion Risks with Kadcyla and Herceptin

Confusion between the names of two popular breast cancer drugs may cause serious medical errors, according to a warning issued by federal health officials.   

The FDA issued a safety warning for Kadcyla and Herceptin yesterday, urging caution when referring to the drugs for reference and prescription purposes.

Officials indicate that many third party health record systems and prescription pharmacy processing systems are mixing up the drugs when health care systems refer to Herceptin and Kadcyla by their non-brand names, which are respectively trastuzumab and ado-trastuzumab emtansine.

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The Roche breast cancer drug Kadcyla, was recently approved by the FDA on February 22, 2013. Kadcyla is known by its nonproprietary name as ado-trastuzumab emtansine, and is used to treat HER2-positive breast cancer that has spread to other parts of the body among patients who have already received treatment with Herceptin and a taxane chemotherapy.

Herceptin is known generically as trastuzumab, and is also used to treat HER2-positive breast cancer tumors.

The similarity between the two non-proprietary names is causing some confusion and in some cases, medical errors. During clinical trials, researchers discovered four patients were given doses of Herceptin instead of Kadcyla, a mistake which can cause severe medical side effects.

The recommended dose for Kadcyla is 3.6 mg, with strong warnings against higher doses. Patients involved in the clinical trials were supposed to receive a 6 mg dose of Herceptin and in some cases received a 6 mg dose of Kadcyla instead.

The FDA also found many internet sites were incorrectly referring to Kadcyla by its United States Adopted Name (USAN), trastuzumab emtansine. This reference omitted the “ado” prefix and hyphen, resulting in further confusion between the two drugs.

The mix up, along with the confusion in other electronic health and prescription systems prompted the FDA to issue a strong advisory about the risks associated with confusing the names of the two drugs. As part of the warning, the FDA recommends the full non-proprietary names be used along with the brand names as well. Using both names to reference the correct drug will prevent medical errors and ensure adverse events are reported for the correct drug.

Since the confusion was discovered, Roche developed new packaging for Kadcyla to help differentiate it from Herceptin and reduce any further errors.

Breast cancer remains one of the most common types of cancer in the United States. More than 200,000 new diagnoses were reported in 2011. The Roche drug Herceptin continues to be the leading treatment for HER2-positive breast cancer.


  • NancyJune 25, 2022 at 6:47 pm

    I had chemo and double mastectomy and then started treatments with kadcyla prior to my 4th treatment I developed nuerapathy and now I can not walk very good and I have constant pain and burning in my feet we have tried everything and nobody can tell me whether this is temporary or permanent please help me

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