Anaphylaxis with Xolair is a rare occurrence, approximately 0.2%. A recent study published in the Journal of Allergy and Clinical Immunology titled “Anaphylactic reactions associated with omalizumab administration: Analysis of a case-control study” looked to clarify the circumstances and risk factors associated with anaphylaxis to Xolair.
Xolair or omalizumab is indicated for moderate to severe persistent asthma and chronic idiopathic or chronic spontaneous urticaria. After Xolair was approved, the US Food and Drug Administration advised including it in an updated US package insert warning of anaphylaxis with Xolair, although the risk is small, it is possible.
In the study published, anaphylaxis with Xolair occurred most frequently within the first 3 doses and within 1 hour of dosing. In contrast, a previous analysis, a delay between the administration of Xolair (omalizumab) and the onset of anaphylaxis was observed. This delay prompted the suggestion of prolonged in office observation times. The reasons for this discrepancy between the two studies are not apparent.
What researchers can not figure out though, is the mechanism of action of anaphylaxis with Xolair (omalizumab). There was no IgE mediated event found underlying anaphylactic episodes due to the administration of Xolair. It has been hypothesized that they are due to a reaction to polysorbate, an excipient in the the preparation.
Although anaphylaxis with Xolair remains a rare event, when prescribing omalizumab, health care providers should consider these observations along with clinical benefits and should adhere to recommended clinical guidance regarding monitoring for anaphylaxis.
None of the anaphylactic episodes in the study resulted in disability or death. Although 40% of them were considered life-threatening and 20% required hospitalization. Treatment of the anaphylaxis included the use of antihistamines, epinephrine, systemic corticosteroids and inhaled Beta-agonists.
To read more about Xolair in our other blog posts, you can click below. If you have any questions if Xolair is the right medication for you, contact your local allergist or allergy doctor.