Omalizumab-associated anaphylactic reactions reported between January 2007 and June 2008

Anaphylaxis associated with omalizumab treatment is a growing concern. The broader context in which omalizumab-associated allergic reactions occur has not been well described.

To identify and characterize recently reported anaphylactic reactions associated with omalizumab administration.

The US Food and Drug Administration Adverse Event Reporting System reports between January 1, 2007, and June 30, 2008, were queried for new reactions primarily suspected to be due to omalizumab. Reaction characteristics were analyzed for a reaction descriptor of anaphylactic or anaphylactoid shock or reaction and for dermal, respiratory, cardiovascular, and gastrointestinal reaction descriptor terms that in combination could be interpreted as constituting anaphylaxis. Associated narratives for these reports were obtained and were examined further.

There were 85 cases with an anaphylaxis descriptor and 33 cases without a descriptor of anaphylaxis but with multisystem allergic reactions (mostly respiratory and skin or mucosal) that were consistent with anaphylaxis. Of these 118 cases, 32 were after the first dose and 14 were after the second dose of omalizumab. Seventy-seven of the 118 cases were categorized as requiring hospital admission or prolongation, had life-threatening reactions, underwent treatment with epinephrine or corticosteroids, or had omalizumab treatment withheld or discontinued. Nineteen of the 118 reactions were described as occurring within 1 hour of omalizumab injection.

Allergic reactions to omalizumab continue to be reported. Some patients not labeled as having anaphylaxis have multisystem allergic reactions consistent with anaphylaxis, raising questions about the adequacy of the Food and Drug Administration categorizations. The characteristics of these patient reports point toward a spectrum of systemic allergic reactions associated with omalizumab use.