Reviewed on 1/27/2022

What Is Omalizumab and How Does It Work?

Omalizumab is a prescription medication used to treat Asthma, Chronic Idiopathic Urticaria, and Nasal Polyps.

  • Omalizumab is available under the following different brand names: Xolair.

Dosages of Omalizumab

Adult and pediatric dosage

Injection, single-dose prefilled syringe

  • 75mg/0.5mL
  • 150mg/mL

Injection, lyophilized powder for reconstitution

  • 150mg/vial
  • 125mg/mL after reconstitution 


Adult dosage

  • 150-375 mg SC every 2-4 weeks

Pediatric dosage

  • Children younger than 6 years of age: Safety and efficacy not established
  • Children 6 to 11 years of age: 75-375 mg SC every 2-4 weeks
  • Children 12 years or older: 150-375 mg SC every 2-4 weeks

Chronic Idiopathic Urticaria

Adult dosage

  • 150-300 mg SC every 4 weeks

Pediatric dosage

  • Children younger than 12 years of age: Safety and efficacy not established
  • Children 12 years of age or older: 150-300 mg SC every 4 weeks 

Nasal Polyps

Adult dosage

  • 75-600 mg SC every 2-4 weeks

Dosage Considerations – Should be Given as Follows: 

  • See "Dosages."

What Are Side Effects Associated with Using Omalizumab?

Common side effects of Omalizumab include:

  • rash, 
  • fever, 
  • nosebleeds, 
  • joint pain, 
  • bone fractures, 
  • arm or leg pain, 
  • nausea, 
  • vomiting, 
  • diarrhea, 
  • stomach pain, 
  • headache, 
  • dizziness, 
  • tiredness, 
  • ear pain, 
  • ear infection, 
  • pain, bruising, swelling, or irritation at the injection site, 
  • stuffy nose
  • sneezing, 
  • sinus pain, 
  • cough, and 
  • sore throat

Serious side effects of Omalizumab include:

  • hives, 
  • itching, 
  • anxiety, 
  • fear, 
  • lightheadedness
  • flushing (warmth, redness, or tingly feeling), 
  • wheezing
  • cough, 
  • shortness of breath, 
  • difficulty breathing, 
  • nausea, 
  • vomiting, 
  • severe or watery diarrhea, 
  • numbness or tingling in the arms or legs, 
  • fever, 
  • muscle pain, 
  • rash within a few days after receiving an injection, 
  • ear pain or full feeling, 
  • trouble hearing, 
  • drainage from the ear, 
  • fussiness in a child, 
  • chest pain or pressure, 
  • pain spreading to the jaw or shoulder
  • sudden numbness or weakness, 
  • problems with vision or speech, 
  • coughing up blood, and
  • swelling or redness in an arm or leg

Rare side effects of Omalizumab include:

  • none 

This is not a complete list of side effects and other serious side effects or health problems may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Omalizumab?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

  • Omalizumab has no noted severe interactions with any other drugs. 
  • Omalizumab has no noted serious interactions with any other drugs. 
  • Omalizumab has no noted moderate interactions with any other drugs. 
  • Omalizumab has no noted minor interactions with any other drugs. 

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this drug, tell your doctor or pharmacist of all the drugs you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

What Are Warnings and Precautions for Omalizumab?


  • Severe hypersensitivity reaction to omalizumab or any of its excipients

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Omalizumab?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Omalizumab?”


  • Risk of anaphylaxis may occur up to 24 hours after any dose, even if no reaction to the first dose; advise patients to carry emergency self-treatment; discontinue if severe hypersensitivity reaction occurs
  • Once therapy has been established, administration by prefilled syringe outside of a healthcare setting by a patient or a caregiver may be appropriate for selected patients; patient selection, determined by healthcare provider in consultation with patient, should take into account the pattern of anaphylaxis events seen in premarketing clinical trials and postmarketing spontaneous reports, as well as individual patient risk factors (eg, prior history of anaphylaxis), ability to recognize signs and symptoms of anaphylaxis, and ability to perform subcutaneous injections with prefilled syringe with proper technique according to prescribed dosing regimen and instructions for use
  • Do not discontinue systemic or inhaled corticosteroids abruptly upon initiating omalizumab; decrease corticosteroids gradually over weeks/months; use with corticosteroids has not been evaluated in patients with CIU
  • Arthritis/arthralgia, rash, fever, and lymphadenopathy reported
  • Malignant neoplasms were observed; malignancy rate was 0.5% compared to 0.2% of controls in clinical trials; a 5-year study found difference in the rates of cancer between omalizumab-treated patients and those who were not treated, but due to limitations of the study, increased cancer risk cannot be ruled out
  • Monitor patients at high risk for geohelminth infection while taking omalizumab
  • Monitor for eosinophilia, vasculitic rash, worsening pulmonary symptoms, cardiac complications, and/or neuropathy, especially upon reduction of oral corticosteroids
  • Not shown to alleviate asthma exacerbations acutely; not for use in acute bronchospasm or status asthmaticus; patients should seek medical advice if their asthma remains uncontrolled or worsens after initiation of treatment with therapy
  • Elevated serum total IgE levels may persist for up to 1 year following discontinuation; do not use serum total IgE levels obtained younger than 1 year following discontinuation to reassess dosing regimen for asthma or nasal polyps

Pregnancy and Lactation

  • Exposure during pregnancy showed no increase in rate of major birth defects or miscarriage;
  • Increased rate of low birth weight among registry infants compared to infants in the other cohorts reported, despite average gestational age at birth; however, women taking the drug during pregnancy also had more severe asthma, which makes it difficult to determine whether low birth weight is due to drug or disease severity
  • Monoclonal antibodies, such as omalizumab, are transported across placenta in a linear fashion as pregnancy progresses; potential effects on fetus are likely to be greater during second and third trimesters of pregnancy
  • In women with poorly or moderately controlled asthma, evidence demonstrates that there is increased risk of preeclampsia in the mother and prematurity, low birth weight, and small for gestational age in the neonate; level of asthma control should be closely monitored in pregnant women and treatment adjusted as necessary to maintain optimal control
  • Human IgG antibodies are known to cross the placental barrier; therefore, drugs may be transmitted from mother to developing fetus.
  • Majority of infants (80.9%, 186/230) in pregnancy exposure registry were breastfed; events categorized as “infections and infestations” were not significantly increased in infants who were exposed through breastfeeding compared with infants who were not breastfed, or infants who were breastfed without exposure
Medscape. Omalizumab.

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