OverviewDosageSide EffectsInteractionsHalf-Life

Generic Name: Omalizumab

Brands: Xolair

Class: Monoclonal antibodies

Availability: Prescription needed

Molecular Formula: C6450H9916N1714O2023S38

Substance UNII: 2P471X1Z11

Boxed Warning

This information comes from DailyMed, an FDA label information provider.


Anaphylaxis presenting as bronchospasm, hypotension, syncope, urticaria, and/or angioedema of the throat or tongue, has been reported to occur after administration of XOLAIR. Anaphylaxis has occurred as early as after the first dose of XOLAIR, but also has occurred beyond 1 year after beginning regularly administered treatment. Because of the risk of anaphylaxis, observe patients closely for an appropriate period of time after XOLAIR administration. Health care providers administering XOLAIR should be prepared to manage anaphylaxis that can be life-threatening. Inform patients of the signs and symptoms of anaphylaxis and instruct them to seek immediate medical care should symptoms occur [see WARNINGS AND PRECAUTIONS (5.1) and ADVERSE REACTIONS (6.16.3)].

What Is Xolair?

Xolair is a monoclonal antibody. It is the brand name of the drug omalizumab.

What Is Xolair Used For?

Xolair can treat severe and persistent allergic asthma that does not respond to antihistamine treatments in individuals who are at least 6 years old. Xolair can also treat chronic idiopathic urticaria (CIU), or chronic hives, in individuals who are at least 12 years of age.

How Does Xolair Work?

Experts are not 100% sure how Xolair works. However, they believe it might work for allergic asthma by binding to a substance called immunoglobulin E (IgE).

Now, the immune system produces IgE when it detects allergens in the body, such as pollen or dander. IgE then attaches to high-affinity IgE receptors (FcεRI) on mast cells (mastocytes, labrocytes), a type of immune cell. This attachment in turn triggers the release of chemicals like histamine. These chemicals can attack foreign invaders (like allergens), but can also result in airway inflammation and trigger asthma attacks. Therefore, by binding to IgE, Xolair can prevent IgE from attaching to mast cells, thereby inhibiting the release of inflammatory substances.

This medication can also simply reduce the sheer number of FcεRI receptors, which means there are fewer places to which IgE can bind. This fact consequently means that there are less opportunities for IgE to trigger inflammatory processes.

How Long Does It Take for Xolair to Work?

Xolair can take several months to begin working for allergic asthma. When used for chronic hives, it can take a week or more to work. How quickly this medication starts to become effective can differ from person to person based on different factors.

Do Not Use Xolair If:

There are several situations where this medication may not be the right choice for you. According to the FDA, the following should not use Xolair:

  • Those who have had a severe hypersensitivity reaction to this medication or any ingredients it contains
  • There is a boxed warning for this medication for hypersensitivity reactions like anaphylaxis. This could occur even after a year of receiving the medication.

Please note that this list may not be complete, and there may be other situations where use of this medication is not advisable.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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