Eli Lilly and Co. has changed the labelling on its antipsychotic Zyprexa to avoid confusion with Pfizer Inc.'s allergy medicine Zyrtec after some patients were given the wrong drug.
Lilly said in a letter to psychiatrists and pharmacists that it had received 79 reports of such mix-ups since Zyprexa, which is used to treat schizophrenia and bipolar disorder, was introduced in 1996. The letter, dated January 26, was posted February 8, 2005, on the US Food and Drug Administration (FDA)'s Medwatch Web site.
Patients with psychological disorders who take Zyrtec instead of their regular Zyprexa could be at risk of relapse, but Lilly spokeswoman Heather Lusk said February 9, 2005, that the company had not received reports of such cases.
Four patients required hospitalization because of the confusion, she said. Those cases involved cardiac arrhythmia, blood pressure changes or changes in the central nervous system, though she was unable to provide details.
The most frequently reported effect from the switched medication was excessive sleepiness, which is listed as a potential side effect for both drugs, Lusk said.
People who received Zyprexa instead of Zyrtec might notice sleepiness, dry mouth or dizziness but were unlikely to experience any changes in mood, she said.
Lilly consulted the FDA about the labelling change in 2003 because of the volume of reports and comments from the Institute for Safe Medication Practices, a nonprofit group that monitors drug safety, Lusk said.
The mix-ups might have occurred because of similarities in the drugs' names and dosage guidelines and because they generally are stored close to each other on pharmacy shelves, Indianapolis-based Lilly said in the letter.
Lilly changed the labelling on Zyprexa from all capital letters to ZyPREXA and highlighted the lettering in yellow to reduce confusion. The company also said it has started direct mail and trade journal advertising and other measures to make pharmacists aware of the errors.
Zyprexa is Lilly's top seller, with sales of over $1 billion last year. Pfizer's Zyrtec is the most prescribed antihistamine in the United States.