Xolair for idiopathic anaphylaxis was recently studied in a randomized double-blind, placebo-controlled study. We have discussed idiopathic anaphylaxis in the past in a blog post.
It is a diagnosis of exclusion, so there is no inciting agent. Epinephrine followed by systemic steroids are the mainstays of therapy for acute events. There is no prophylactic therapy that reliably prevents anaphylaxis.
Anaphylaxis is a systemic reaction associated with the release of mediators from mast cells and basophils. Signs and symptoms are flushing, hives, congestion, eye irritation, bronchospasm, swelling of the tongue, throat, palms and soles, GI cramping, light headedness and loss of conciousness.
Common causes are allergic reactions to foods, drugs or stinging insects. A factor is identified in up to 50% of the patients with recurrent episodes. Idiopathic anaphylaxis is categorized as frequent (2 episodes in past 2 months or greater than 6 episodes in past year) or infrequent (less than 6 episodes a year).
Management consists of epinephrine, airway protection and support of circulation.
Xolair (omalizumab) is approved for the treatment of moderate to severe asthma and chronic urticaria. (More recently nasal polyps). Xolair targets IgE and several reports showed it worked for idiopathic anaphylaxis, systemic mastocytosis or mast cell activation syndrome.
A recent study completed 16 patients in a trial of Xolair for idiopathic anaphylaxis. No statistically significant difference was demonstrated between the placebo and treated groups. There was a trend for efficacy in the treatment group, but it wasn’t significant.
The key messages from this study are:
- Xolair for idiopathic anaphylaxis cannot be expected to prevent subsequent episodes of anaphylaxis, and if it administered, careful monitoring is required to evaluate success.
- Because idiopathic anaphylaxis can decrease in severity and frequency, with time, any intervention must be evaluated on a case by case basis for efficacy.
Although there are several case reports in the literature that relate efficacy of Xolair for idiopathic anaphylaxis, these studies only enrolled 1 case.