About This Topic

The Xolair (omalizumab) Dosing Calculator is a clinical support tool for healthcare professionals to determine the appropriate subcutaneous dosage and administration frequency for patients. The calculation depends on the specific indication, patient body weight, and baseline serum total IgE level, as outlined in the official prescribing information.

This information serves as a guide to understanding the outputs and proper use of the calculator. It is not a substitute for clinical judgment or the full prescribing information.

Outputs Explained

After entering the required patient data, the calculator provides the following key outputs for a dosing schedule:

• Recommended Dose: The total amount of omalizumab in milligrams (mg) to be administered per session.
• Administration Frequency: The time interval between doses, typically “Every 2 weeks” or “Every 4 weeks”.
• Required Administration: A breakdown of the number of 75 mg and/or 150 mg prefilled syringes or auto-injectors needed to achieve the total recommended dose.
• Total Injections: The total number of separate subcutaneous injections required per administration session.

How to Use the Calculator

To ensure accurate dosing recommendations, follow these steps when using the tool:

1. Select Indication: Choose the appropriate condition for which Xolair is being prescribed: “Moderate to Severe Persistent Allergic Asthma / CRSwNP” or “Chronic Spontaneous Urticaria (CSU)”.
2. Enter Body Weight: For Asthma or CRSwNP, input the patient’s pre-treatment body weight and select the unit (kg or lbs). This step is not required for CSU.
3. Enter IgE Level: For Asthma or CRSwNP, input the patient’s pre-treatment baseline serum total IgE level in IU/mL. This step is not required for CSU.
4. Calculate: Click the “Calculate Dose” button to generate the dosing recommendation based on the provided inputs.

Dosing Overview

Dosing for Xolair is indication-specific and must be determined before the first dose and re-evaluated for any significant changes in body weight.

• Allergic Asthma & CRSwNP: Dosing is based on a chart that correlates body weight (20-150 kg) and baseline serum IgE level (30-700 IU/mL). Doses range from 75 mg to 375 mg administered every 2 or 4 weeks. Patients outside these ranges are not candidates for Xolair therapy.
• Chronic Spontaneous Urticaria (CSU): Dosing is not dependent on body weight or IgE level. The recommended dose is 150 mg or 300 mg every 4 weeks. The 300 mg dose may be considered for patients who do not respond to the 150 mg dose.

Switching Therapy

Switching a patient from another biologic therapy to Xolair (omalizumab) requires careful clinical consideration. There are no specific guidelines in the prescribing information for switching. The decision should be made by a qualified healthcare professional, considering the patient’s clinical history, disease activity, and the pharmacokinetic properties of both medications. A suitable washout period may be necessary.

Missed Dose Protocol

If a patient misses a dose of Xolair, the next dose should be administered as soon as possible. Subsequently, the dosing schedule should be adjusted to maintain the recommended interval (e.g., every 2 or 4 weeks) from the date of the most recent administration. Do not administer a double dose to make up for a missed one.

Safety Alerts

Xolair carries a boxed warning for Anaphylaxis. Anaphylaxis has presented as bronchospasm, hypotension, syncope, urticaria, and/or angioedema of the throat or tongue. It has been reported to occur after the first dose or after many doses, and can occur hours after administration. Administer Xolair only in a healthcare setting prepared to manage anaphylaxis. Observe patients for an appropriate period after administration. For a complete list of contraindications, warnings, and precautions, consult the full prescribing information.

Frequently Asked Questions (FAQ)

• What should I do if a patient’s weight or IgE is outside the calculator’s range?

  If a patient’s body weight or IgE level falls outside the ranges specified in the dosing charts (20-150 kg for weight, 30-700 IU/mL for IgE), they are not considered a candidate for Xolair therapy for allergic asthma or CRSwNP. Refer to the prescribing information for guidance.

• Why isn’t weight or IgE required for the Chronic Spontaneous Urticaria (CSU) indication?

  The approved dosing for CSU is a fixed regimen (150 mg or 300 mg every 4 weeks) and has been shown to be effective without adjusting for body weight or IgE levels.

• How is the number of injections determined?

  The calculator determines the most efficient combination of 150 mg and 75 mg syringes to achieve the total calculated dose. For example, a 225 mg dose is given as one 150 mg injection and one 75 mg injection.

• Can this calculator be used for pediatric patients?

  Yes, for approved indications. Xolair is approved for allergic asthma in patients 6 years and older, CRSwNP in adults 18 years and older, and CSU in patients 12 years and older. The dosing tables are applicable within the specified age groups and weight/IgE limits.

• Is the dosing for allergic asthma and CRSwNP the same?

  Yes, the dosing for moderate to severe persistent allergic asthma and Chronic Rhinosinusitis with Nasal Polyps (CRSwNP) follows the same weight and IgE-based dosing chart.

• What happens if a patient’s body weight changes significantly?

  Dose determinations should be based on body weight at the initiation of therapy. For allergic asthma and CRSwNP, the dose should be re-evaluated and adjusted if the patient has a significant change in body weight.

• Does the calculator account for both prefilled syringes and auto-injectors?

  The calculator’s output for “injections” applies to both prefilled syringes and auto-injectors, as they are available in the same 75 mg and 150 mg strengths. The choice of device is up to the healthcare provider and patient.

• Can a total dose of over 375 mg be administered?

  No, the maximum recommended dose per administration session according to the official dosing charts is 375 mg.

References

1. XOLAIR® (omalizumab) Prescribing Information. Genentech, Inc. and Novartis Pharmaceuticals Corporation. Updated February 2024.
2. Xolair for Healthcare Professionals. Genentech USA, Inc.
3. Xolair (omalizumab) European public assessment report (EPAR). European Medicines Agency.
4. Xolair Professional Dosing Information. Drugs.com.