Xolair (Omalizumab)

What Is Xolair and What Is It Used For?

Quick Answer: Xolair (omalizumab) is a prescription biologic medication that blocks IgE antibodies in the body. It is approved for treating severe allergic (IgE-mediated) asthma and chronic rhinosinusitis with nasal polyps in patients whose symptoms remain uncontrolled despite standard therapy.

Xolair contains the active substance omalizumab, an engineered protein that closely resembles naturally occurring human antibodies. Omalizumab belongs to a class of drugs called monoclonal antibodies – laboratory-made proteins designed to target specific molecules in the body. In Xolair's case, the target is immunoglobulin E (IgE), an antibody that plays a central role in allergic responses.

IgE is produced by the immune system in response to allergens such as pollen, dust mites, pet dander, and mold. In susceptible individuals, IgE binds to receptors on mast cells and basophils, triggering the release of histamine and other inflammatory chemicals that cause allergic symptoms. Xolair works by intercepting free IgE in the bloodstream before it can attach to these cells, effectively interrupting the allergic cascade at its source.

Severe Allergic Asthma

Xolair is indicated for severe persistent allergic asthma in adults, adolescents, and children aged 6 years and older. It is prescribed as an add-on therapy for patients whose asthma symptoms remain inadequately controlled despite optimized treatment with high-dose inhaled corticosteroids (ICS) and long-acting beta-agonists (LABA). By reducing circulating IgE levels, Xolair decreases airway inflammation, reduces the frequency and severity of asthma exacerbations, and may allow patients to reduce their dependence on oral corticosteroids.

Clinical trials have demonstrated that Xolair reduces asthma exacerbation rates by approximately 25–50% compared to placebo in appropriately selected patients. The Global Initiative for Asthma (GINA) guidelines recognize omalizumab as a Step 5 add-on therapy for patients with severe allergic asthma and elevated IgE levels.

Chronic Rhinosinusitis with Nasal Polyps

Xolair is also approved for the treatment of chronic rhinosinusitis with nasal polyps (CRSwNP) in adults aged 18 years and older whose symptoms are not adequately controlled by intranasal corticosteroids alone. Nasal polyps are soft, non-cancerous growths on the lining of the nasal passages or sinuses that can cause persistent nasal congestion, reduced sense of smell, postnasal drip, and facial pressure.

In clinical studies, Xolair has been shown to significantly reduce polyp size and improve symptoms such as nasal congestion and loss of smell. The European Position Paper on Rhinosinusitis and Nasal Polyps (EPOS 2020) recommends biologics including omalizumab as a treatment option for patients with CRSwNP who fail to respond adequately to intranasal corticosteroids and who have had previous sinus surgery or are not candidates for surgery.

Mechanism of Action

Omalizumab selectively binds to the Cε3 domain of human IgE, the same region that attaches to high-affinity IgE receptors (FcεRI) on mast cells and basophils. This binding prevents IgE from interacting with its receptors. As a result, free serum IgE levels decrease rapidly after treatment initiation, and over time, the expression of FcεRI receptors on mast cells, basophils, and dendritic cells is also downregulated. This dual mechanism leads to a progressive reduction in allergic responsiveness.

What Should You Know Before Taking Xolair?

Quick Answer: Do not use Xolair if you are allergic to omalizumab or any of its inactive ingredients. Inform your doctor about kidney or liver problems, autoimmune conditions, travel to parasite-endemic regions, or a history of severe allergic reactions (anaphylaxis) before starting treatment.

Contraindications

Xolair must not be used if you have a known hypersensitivity (allergy) to omalizumab or to any of the excipients in the formulation, including arginine hydrochloride, histidine hydrochloride monohydrate, histidine, polysorbate 20, and water for injections. If you suspect you may be allergic to any component, tell your doctor before receiving Xolair.

Warnings and Precautions

Before starting Xolair, talk to your doctor if any of the following apply to you:

• Kidney or liver problems – Xolair has not been extensively studied in patients with significant renal or hepatic impairment, and dose adjustments may be needed.
• Autoimmune conditions – If you have a condition in which your immune system attacks your own body (such as lupus or rheumatoid arthritis), tell your doctor, as Xolair modifies immune function.
• Parasitic infections – If you are travelling to or living in an area where parasitic (helminth) infections are common, be aware that Xolair may weaken your body's ability to fight such infections, as IgE plays a role in antiparasitic immunity.
• History of anaphylaxis – If you have previously experienced a severe allergic reaction to any substance (drug, insect sting, food), you may be at increased risk of anaphylaxis during Xolair treatment.

Conditions Xolair Is Not Intended For

Xolair is not designed to treat or prevent the following conditions, as it has not been studied for these uses:

• Acute allergic reactions or anaphylaxis from any cause
• Hyperimmunoglobulin E syndrome (Job syndrome)
• Allergic bronchopulmonary aspergillosis
• Food allergies
• Atopic dermatitis (eczema)
• Allergic rhinitis (hay fever) without nasal polyps

Children and Adolescents

For allergic asthma, Xolair can be used in children aged 6 years and older. It is not recommended for children under 6, as safety and efficacy have not been established in this age group. The pre-filled injection pen is designed for patients aged 12 and older; younger children (6–11 years) should use the pre-filled syringe formulation or the powder and solvent for solution for injection.

For chronic rhinosinusitis with nasal polyps, Xolair is not approved for use in patients under 18 years of age, as clinical studies have not been conducted in this population.

Pregnancy and Breastfeeding

If you are pregnant, think you may be pregnant, or are planning to become pregnant, consult your doctor before using Xolair. Your doctor will weigh the potential benefits against the possible risks. As an IgG1 antibody, omalizumab is expected to cross the placental barrier, particularly during the second and third trimesters. If you become pregnant while receiving Xolair, inform your doctor immediately.

Omalizumab may pass into breast milk. If you are breastfeeding or planning to breastfeed, discuss the risks and benefits with your doctor before continuing treatment.

Driving and Operating Machinery

Xolair is unlikely to affect your ability to drive or operate machinery. However, if you experience dizziness or drowsiness after an injection, avoid driving until these effects have resolved.

How Does Xolair Interact with Other Drugs?

Quick Answer: Xolair has few known drug interactions. It may reduce the effectiveness of antiparasitic medications. Tell your doctor about all medications you are taking, including inhaled corticosteroids and other asthma treatments. Do not stop any prescribed medication without consulting your doctor.

Because Xolair is a monoclonal antibody that specifically targets IgE, it does not undergo hepatic metabolism via cytochrome P450 enzymes and therefore has a low potential for traditional pharmacokinetic drug interactions. However, there are important pharmacodynamic considerations that clinicians and patients should be aware of.

Tell your doctor, pharmacist, or nurse if you are taking, have recently taken, or might take any other medicines. This is particularly important if you are using:

Since Xolair acts through a specific immunological pathway (IgE blockade) rather than through metabolic enzymes, the risk of traditional drug-drug interactions is minimal. Nevertheless, always provide your healthcare team with a complete list of all medications, supplements, and herbal remedies you are taking.

What Is the Correct Dosage of Xolair?

Quick Answer: Xolair dosing is highly individualized. For allergic asthma, the dose (75–600 mg per injection visit) and frequency (every 2 or 4 weeks) are determined by your body weight and serum IgE level, measured by a blood test before treatment begins. For nasal polyps, the standard dose is 150–600 mg every 2 or 4 weeks, also based on weight and IgE.

Always use Xolair exactly as your doctor has prescribed. Your doctor will determine the appropriate dose based on your body weight and the amount of IgE in your blood, which is measured by a blood test taken before starting treatment. The resulting dose can range from 75 mg to 600 mg per injection visit, administered either every 2 weeks or every 4 weeks.

Adults and Adolescents (Allergic Asthma)

Children (6–11 Years, Allergic Asthma)

Adults (Chronic Rhinosinusitis with Nasal Polyps)

Administration

Xolair is given as a subcutaneous injection (under the skin), not into a vein or muscle. The recommended injection sites are the front of the thigh or the lower abdomen, avoiding the area within 5 cm of the navel. If a caregiver or healthcare professional administers the injection, the outer upper arm may also be used. When multiple injections are required at a single visit, each injection should be given at least 2 cm apart.

The first three doses must always be administered by or under the direct supervision of a healthcare professional. After this, if the doctor considers it appropriate, patients (aged 12 and older) or trained caregivers may perform injections at home.

Missed Dose

If you miss a scheduled injection, administer the dose as soon as you remember and contact your doctor to reschedule your next dose. Do not double the dose to make up for a missed one.

Overdose

No dose-limiting toxicity has been identified in clinical trials with Xolair at doses up to 4,000 mg as a single intravenous dose. However, if you suspect an overdose, contact your doctor or local poison control center immediately. Treatment of overdose is supportive and symptomatic.

Time to Effect

You may not notice improvement immediately. For nasal polyps, clinical benefit has been observed as early as 4 weeks after starting treatment. For allergic asthma, it generally takes 12 to 16 weeks before the full therapeutic effect is achieved. Your doctor will assess your response to treatment periodically.

What Are the Side Effects of Xolair?

Quick Answer: Common side effects include injection site reactions (pain, swelling, redness), headache, upper abdominal pain, and joint pain. In children, fever is very common. Serious but rare side effects include anaphylaxis. Seek immediate medical attention if you experience difficulty breathing, swelling of the face or throat, rapid heartbeat, or dizziness after injection.

Like all medicines, Xolair can cause side effects, although not everybody gets them. Most side effects are mild to moderate in severity, but some can be serious and require immediate medical attention.

Serious Side Effects

Side Effects by Frequency

Reporting Side Effects

If you experience any side effects, including those not listed above, tell your doctor, pharmacist, or nurse. You can also report side effects directly to your national medicines regulatory authority (e.g., the FDA MedWatch program in the United States, the Yellow Card Scheme in the United Kingdom, or the EMA in the European Union). By reporting side effects, you help provide more information on the safety of this medicine.

How Should You Store Xolair?

Quick Answer: Store Xolair in a refrigerator at 2–8°C. Do not freeze. Keep in the original packaging to protect from light. The pre-filled pen may be stored at room temperature (up to 25°C) for a maximum of 48 hours before use.

Proper storage is essential to maintain the efficacy and safety of Xolair. Follow these guidelines:

• Refrigerate: Store at 2–8°C (36–46°F) in the original carton to protect from light.
• Do not freeze: Freezing will damage the medication and render it unusable.
• Room temperature: The pre-filled pen or syringe may be kept at room temperature (up to 25°C / 77°F) for a total of 48 hours before use. After 48 hours at room temperature, the product must be discarded.
• Inspect before use: The solution should be clear to slightly opalescent, colorless to slightly brownish-yellow. Do not use if the solution is distinctly cloudy, discolored, or contains visible particles.
• Check expiry date: Do not use after the expiration date printed on the label and carton.
• Keep out of reach of children.
• Do not use a package that appears damaged or shows signs of tampering.

What Does Xolair Contain?

Quick Answer: Each Xolair pre-filled pen contains omalizumab as the active ingredient (available in 75 mg, 150 mg, and 300 mg strengths). Inactive ingredients include arginine hydrochloride, histidine, polysorbate 20, and water for injections.

Active Ingredient

The active substance is omalizumab. One pre-filled pen containing 0.5 mL of solution for injection delivers 75 mg of omalizumab. Higher-strength pens deliver 150 mg (in 1.0 mL) or 300 mg (in 2.0 mL).

Inactive Ingredients (Excipients)

• Arginine hydrochloride
• Histidine hydrochloride monohydrate
• Histidine
• Polysorbate 20
• Water for injections

Appearance and Packaging

Xolair solution for injection is a clear to slightly opalescent, colorless to slightly brownish-yellow liquid supplied in a pre-filled injection pen. Each pen is individually packaged. Multi-packs containing 3 or 6 pens are also available, although not all pack sizes may be marketed in your country.

How Do You Self-Inject Xolair at Home?

Quick Answer: After your first three doses under medical supervision, you may be able to self-inject Xolair at home using the pre-filled pen. Let the pen reach room temperature, choose an injection site on the thigh or abdomen, clean the area, remove the cap, press the pen at 90° against the skin, and hold until the green indicator stops moving. Dispose of the pen in a sharps container.

If your doctor determines that you (or a caregiver) can administer Xolair at home, you must first receive thorough training from a healthcare professional on the correct injection technique and how to recognize and manage early signs of anaphylaxis. The pre-filled pen is designed for patients aged 12 years and older.

Step-by-Step Instructions

1. Prepare: Remove the pen from the refrigerator and let it sit at room temperature, unopened, for at least 30 minutes. If you need multiple pens for a full dose, take all of them out at the same time. Gather your supplies: alcohol swab, cotton ball or gauze, sharps container, and adhesive bandage.
2. Inspect: Check the solution through the viewing window. It should be clear to slightly opalescent, colorless to slightly brownish-yellow. Small air bubbles are normal. Do not use if the solution contains particles, looks distinctly cloudy or brown, or if the pen is damaged or expired.
3. Choose injection site: Use the front of the thigh or the lower abdomen (avoid the 5 cm area around the navel). Do not inject into skin that is tender, bruised, red, scaly, or hard, or into areas with scars or stretch marks. If multiple injections are needed, space them at least 2 cm apart.
4. Clean: Wash your hands thoroughly. Clean the injection site with an alcohol swab and allow it to air-dry. Do not touch or blow on the cleaned area.
5. Remove the cap: Pull the cap straight off in the direction of the arrow. Do not replace the cap once removed.
6. Position: Hold the pen comfortably with the needle guard pointing directly at the skin, at a 90-degree angle.
7. Inject: Press the pen down firmly against the skin. Listen for the first click, which signals the injection has begun. Continue holding the pen steady.
8. Monitor: Watch the green indicator in the viewing window as it progresses.
9. Complete: Listen for the second click, which signals the injection is nearly complete. Continue holding until the green indicator has stopped moving, then remove the pen. The needle retracts automatically.
10. Check: Verify that the green indicator fills the viewing window completely. If it does not, contact your doctor.
11. Dispose: Place the used pen in a sharps disposal container immediately. Do not attempt to recap the pen.

References

1. European Medicines Agency (EMA). Xolair (omalizumab) – Summary of Product Characteristics. EMA EPAR: Xolair. Last updated 2025.
2. U.S. Food and Drug Administration (FDA). Xolair (omalizumab) Prescribing Information. FDA Label. 2024.
3. Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention. 2024. Available at: ginasthma.org.
4. Normansell R, Walker S, Milan SJ, et al. Omalizumab for asthma in adults and children. Cochrane Database of Systematic Reviews. 2014;(1):CD003559. doi:10.1002/14651858.CD003559.pub4.
5. Fokkens WJ, Lund VJ, Hopkins C, et al. European Position Paper on Rhinosinusitis and Nasal Polyps 2020 (EPOS 2020). Rhinology. 2020;58(Suppl S29):1–464. doi:10.4193/Rhin20.600.
6. Gevaert P, Omachi TA, Corber J, et al. Efficacy and safety of omalizumab in nasal polyposis: 2 randomized phase 3 trials. Journal of Allergy and Clinical Immunology. 2020;146(3):595–605. doi:10.1016/j.jaci.2020.05.032.
7. Hanania NA, Alpan O, Hamilos DL, et al. Omalizumab in severe allergic asthma inadequately controlled with standard therapy: a randomized trial. Annals of Internal Medicine. 2011;154(9):573–582. doi:10.7326/0003-4819-154-9-201105030-00002.
8. World Health Organization (WHO). WHO Model List of Essential Medicines – 23rd List, 2023. Geneva: WHO; 2023.

Editorial Team