The Food and Drug Administration (FDA) has requested that Genentech, Inc. add a boxed warning to the product label for omalizumab, marketed as Xolair.

The drug was approved in 2003 to treat adults and adolescents (12 years of age and above) with moderate to severe persistent asthma who have tested positive for a perennial allergen -- like pollen, grass or dust -- and whose symptoms are inadequately controlled with inhaled steroids.

The boxed warning emphasizes that Xolair, used to treat patients with asthma related to allergies, may cause anaphylaxis. Anaphylaxis may include trouble breathing, chest tightness, dizziness, fainting, itching and hives, and swelling of the mouth and throat.

In addition, FDA has asked Genentech to revise the Xolair label and provide a Medication Guide for patients to strengthen the existing warning for anaphylaxis.

Anaphylaxis was reported following administration of Xolair in clinical trials and was therefore, discussed in the initial product labeling. The cases were reported at a frequency of approximately one in a thousand patients (0.1%).

Due to the nature of continued reports in the post-marketing experience, including their life-threatening potential, frequency, and the possibility for the delayed onset of anaphylaxis, FDA has now requested that Genentech, Inc., add the boxed warning and strengthen the existing warning.

The strengthened warning includes the possibility of a patient developing anaphylaxis after any dose of Xolair, even if there was no reaction to the first dose. Also, anaphylaxis after administration of Xolair may be delayed up to 24 hours after the dose is given.

Health care providers should be prepared to manage life-threatening anaphylaxis following Xolair administration and observe patients for at least two hours after an injection. Following administration of Xolair, patients should also carry and know how to initiate emergency self-treatment for anaphylaxis.