Healthcare practitioners have been notified about medication dispensing and prescribing errors that are occurring between olanzapine (Zyprexa), an atypical antipsychotic, and cetirizine (Zyrtec), an antihistamine. These reports include cases where olanzapine was incorrectly dispensed for cetirizine and vice versa, which could lead to adverse events or potential relapse in patients suffering from schizophrenia or bipolar disorder. Olanzapine is a product of Eli Lilly; cetirizine is a product of Pfizer.

Olanzapine is indicated for short-term management of schizophrenia and acute mixed or manic episodes associated with bipolar I disorder as well as for maintenance treatment of schizophrenia and bipolar disorder. Cetirizine is an antihistamine indicated for the treatment of allergic rhinitis and chronic urticaria.

The FDA notes that substitutions may be due to similarities in brand name that can lead to storage near each other and to similarities in available dosage strengths (5 mg and 10 mg tablets) and dosing interval (once daily).

To prevent future errors, Eli Lilly has changed the packaging label on bottles of olanzapine 10 mg from ZYPREXA to ZyPREXA, and has initiated an awareness campaign to draw attention to the potential problem.

Prescribers are urged to include brand and generic names in print to clearly communicate written prescriptions.