Anti-IgE Monoclonal Antibody Pregnancy: A moderate amount of data on pregnant women (between 300 and 1,000 pregnancy outcomes) from a pregnancy registry and post-marketing spontaneous reports indicates no malformative or foeto/neonatal toxicity; in the EXPECT registry of 250 pregnant women with asthma the prevalence of major congenital anomalies was similar to disease-matched controls (8.1% vs 8.9%). Omalizumab crosses the placental barrier, and animal studies do not indicate direct or indirect harmful effects on reproduction. If clinically needed, use may be considered during pregnancy. Breast-feeding: omalizumab is expected to be present in human milk but no effects on breast-fed newborns/infants are anticipated, and use may be considered if clinically needed.

Omalizumab (Dermatology — Chronic Urticaria)

Brand names: Xolair

In dermatology, omalizumab is a monoclonal anti-IgE antibody given by subcutaneous injection for chronic spontaneous (idiopathic) urticaria that remains symptomatic despite antihistamines.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Chronic spontaneous urticaria (CSU): 300 mg by subcutaneous injection every four weeks. Each 300 mg dose is given as two subcutaneous injections of 150 mg

Route: Subcutaneous injection only - omalizumab must NOT be administered by the intravenous or intramuscular route

Frequency: Every 4 weeks

Max: The maximum recommended dose stated in §4.2 is 600 mg omalizumab every two weeks; this applies to the IgE- and weight-based asthma and CRSwNP dosing, whereas CSU dosing is the fixed 300 mg every 4 weeks and is not determined by IgE level or body weight

Treatment should be initiated by physicians experienced in the diagnosis and treatment of severe persistent asthma, chronic rhinosinusitis with nasal polyps (CRSwNP) or chronic spontaneous urticaria. Prescribers are advised to periodically reassess the need for continued therapy in CSU. Fetched SPC is Omlyclo 150 mg solution for injection in pre-filled syringe (https://www.medicines.org.uk/emc/product/15917/smpc). PAEDIATRIC: in CSU the safety and efficacy of omalizumab in patients below the age of 12 years have not been established and no data are available (below 6 years for allergic asthma; below 18 years for CRSwNP). Verify any under-18 use against a children's formulary. OTHER INDICATIONS IN THE SAME SPC (do not apply to CSU): for allergic asthma and CRSwNP the dose and frequency are determined by baseline total IgE (IU/ml) measured before the start of treatment and by body weight (kg), with 75 to 600 mg given in 1 to 4 injections per administration - the dose-determination charts (Tables 2 and 3) were not retrievable from the fetched text, so those regimens cannot be reproduced here. ADMINISTRATION: if more than one injection is needed to achieve the required dose, injections should be divided across two or more injection sites; patients with no known history of anaphylaxis may self-inject or be injected by a caregiver from the 4th dose onwards if a physician determines this is appropriate, after training in injection technique and recognition of the early signs and symptoms of serious allergic reactions. ELDERLY (65 and over): limited data, but no evidence that a different dose is required. The US label (openFDA, XOLAIR) also permits 150 mg or 300 mg subcutaneously every 4 weeks for CSU and notes the 300 mg dose may be given as one 300 mg/2 mL injection or as two 150 mg/mL injections - the fetched UK SPC states only the 300 mg dose given as two 150 mg injections.

Dose adjustments

Renal

There have been no studies on the effect of impaired renal or hepatic function on the pharmacokinetics of omalizumab. Because clearance at clinical doses is dominated by the reticular endothelial system it is unlikely to be altered by renal or hepatic impairment; no particular dose adjustment is recommended, but omalizumab should be administered with caution.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients

Side effects

Headache (common; very common in children 6 to under 12 years)
Injection site reactions such as swelling, erythema, pain and pruritus (common)
Pyrexia (very common in children 6 to under 12 years) and upper abdominal pain (common)
Arthralgia (common); dizziness, syncope, paraesthesia, somnolence, postural hypotension and flushing (uncommon)
Anaphylactic reaction and other serious allergic conditions (rare); angioedema (rare); urticaria, rash, pruritus and photosensitivity (uncommon); idiopathic thrombocytopenia including severe cases (frequency not known)
The CSU-specific §4.8 subsection is truncated at the source-fetch limit; the reactions listed above are from the allergic asthma and CRSwNP safety population (Table 4) - verify the CSU-specific frequencies against the full SPC §4.8

Interactions

No formal drug interaction studies have been performed with omalizumab (US label §7)
In patients with CSU, the use of omalizumab in combination with immunosuppressive therapies has not been studied (US label §7)
In patients with asthma, CRSwNP and IgE-mediated food allergy, concomitant use with allergen immunotherapy has not been evaluated (US label §7)
Interactions are taken from the US prescribing information because the fetched eMC bundle contains no §4.5 section - verify against the full UK SPC §4.5

Clinical monograph

How it works

It binds free immunoglobulin E and lowers its availability to bind mast cells and basophils, reducing the IgE-mediated mast-cell activation that drives the weals and angioedema of chronic urticaria.

Prescribing in practice

Anaphylaxis can occur with omalizumab, so administer where resuscitation facilities are available and observe the patient after injection.
It controls symptoms rather than curing the disease, and urticaria may recur after stopping, so review ongoing need.
Given by subcutaneous injection at intervals; it is an add-on once antihistamine therapy has been optimised.

Monitoring

Monitoring is clinical, using urticaria activity and itch scores to assess response and observing for hypersensitivity reactions around dosing.

Counselling the patient

This treats the symptoms of hives; they may return if treatment is stopped.
Seek emergency help for any signs of a severe allergic reaction such as breathing difficulty or facial swelling.
Continue your antihistamines as advised while on this injection.

Evidence & guidelines

Omalizumab is recommended by NICE for chronic spontaneous urticaria inadequately controlled by antihistamines, supported by the ASTERIA and GLACIAL trials.

Reference: ASTERIA I (Maurer et al. NEJM 2013); ASTERIA II; GLACIAL trial; NICE TA339; MHRA SPC Xolair; EAACI/GA²LEN/EDF/WAO Urticaria Guidelines (2022); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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