Characterization of an anaphylactoid reaction to omalizumab.

BACKGROUND: The novel humanized murine monoclonal antibody omalizumab prevents binding of human IgE to its high-affinity receptor. A contraindication to therapy with omalizumab is allergy to the medication or previous immediate-type hypersensitivity or anaphylaxis to omalizumab or similar medications.

OBJECTIVE: To determine whether a 32-year-old woman with asthma, allergic rhinitis, and idiopathic chronic urticaria and angioedema with anaphylactoid reactions to omalizumab could tolerate the medication in a desensitization protocol.

METHODS: Omalizumab was administered after pretreatment with nonsteroidal anti-inflammatory drugs (ibuprofen, 600 mg) while the patient was closely monitored in an intensive care unit.

RESULTS: Omalizumab was well tolerated using this protocol, but a serum sickness-like reaction developed that required discontinuation of the medication after the seventh dose.

CONCLUSIONS: Our experience suggests that some patients with anaphylactoid reactions to omalizumab can tolerate the medication when pretreated with nonsteroidal anti-inflammatory drugs but that a serum sickness-like illness may develop, requiring discontinued use of the medication.