The FDA issued the alert after reviewing 48 cases of anaphylaxis -- life-threatening allergic reactions -- submitted to the agency from June 2003, when Xolair was approved, through December 2005.
Nearly 15% of the patients required hospitalization. No deaths were reported.
The drug, which is injected, is also known by the generic name omalizumab.
It is approved for use in asthma patients aged 12 and older who have moderate to severe persistent asthma, and who have tested positive for a perennial aerial allergen -- such as pollen, grass, or dust.
The drug is a secondary treatment, recommended for those whose symptoms have not been adequately controlled with inhaled steroids.
Delayed Reaction Possible
The FDA alert warns that patients can have a delayed reaction from two to 24 hours -- or longer -- after injection.
It adds that patients who have not reacted in the past can still develop anaphylaxis following a later dose.
In about 39,500 patients who took Xolair, the FDA says anaphylaxis occurred in at least 0.1% of those treated.
The drug is currently injected in a medical setting once every two or four weeks, depending on the patient, according to an email response from the FDA.
Now, the FDA is asking health care professionals who administer Xolair to observe patients for at least two hours after giving the injection and to be prepared to manage life-threatening anaphylaxis if it occurs.
Also, patients who take Xolair should be told of the possibility of a delayed reaction and be able to recognize the signs and symptoms of anaphylaxis, the FDA says in its alert.
Patients using Xolair should carry medical contact information and an epinephrine auto-injector (EpiPen). They should also be prepared to begin treatment on themselves while they seek immediate medical attention should anaphylaxis occur.
Xolair was the first biologic, or biotechnology product, developed to treat such allergy-related asthma when it was brought to the market in 2003.
At the time of the FDA review, Xolair's maker, Genentech, Inc., reported three cases of anaphylaxis among the 3,507 subjects given the drug in premarketing clinical trials. Two additional cases were not called anaphylaxis at that time, but meet the criteria now being used for the postmarketing cases, the FDA says.
The FDA said in its announcement today that its action is due to the nature of anaphylaxis reports after the drug reached market, including their life-threatening potential, their frequency, and the possibility of delayed onset.
In addition to the boxed warning -- the most serious type -- the FDA is asking Genentech to revise the Xolair label and provide a medication guide for patients to strengthen the existing warning for anaphylaxis. Genentech is a WebMD sponsor.