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Anti-IgE Monoclonal Antibody Pregnancy: Use with caution — limited data; IgG antibody crosses placenta; use only if clearly needed

Omalizumab (Dermatology — Chronic Urticaria)

Brand names: Xolair

Adult dose

Dose: 300 mg SC every 4 weeks
Route: Subcutaneous injection
Frequency: Every 4 weeks
Max: 300 mg per dose
Chronic spontaneous urticaria (CSU) refractory to non-sedating antihistamines; response typically seen within 4-12 weeks; reassess every 6 months; no IgE level testing or weight-based dosing for urticaria (unlike asthma)

Paediatric dose

Dose: Not established for urticaria in <12 years N/A/kg
Route: Subcutaneous
Frequency: Every 4 weeks
Max: 300 mg/dose
Licensed for CSU ≥12 years; specialist paediatric use

Dose adjustments

Renal

No dose adjustment required

Hepatic

No dose adjustment required

Paediatric weight-based calculator

Licensed for CSU ≥12 years; specialist paediatric use

Clinical pearls

  • ASTERIA I and II, GLACIAL trials: omalizumab 300 mg significantly reduced itch severity score and urticaria activity score (UAS7) vs placebo in antihistamine-refractory CSU — NICE TA339 approved
  • Mechanism in CSU: binds free IgE → prevents IgE binding to FcεRI receptors on mast cells → reduces mast cell sensitivity and spontaneous degranulation; serum IgE levels rise on treatment (IgE-omalizumab complex) — do not use IgE level to monitor response
  • NICE TA339: add-on treatment for CSU inadequately controlled with H1-antihistamines (at up to 4× licensed dose) in adults and adolescents ≥12 years; review every 6 months — discontinue if no response at 12 weeks
  • Anaphylaxis risk: present after any dose (not just first); adrenaline auto-injector should be available at every clinic; observe 30 minutes post-injection for first 3 doses — MHRA requirement
  • Distinct from asthma use: fixed 300 mg dose regardless of IgE or weight; no serum IgE testing needed before prescribing for CSU; total IgE rises on treatment and cannot guide response monitoring

Contraindications

  • Known hypersensitivity to omalizumab
  • Acute urticaria without chronic spontaneous component

Side effects

  • Injection site reactions
  • Anaphylaxis (rare, 0.1% — observe for 30 minutes after first 3 doses)
  • Headache
  • Arthralgia
  • Nasopharyngitis

Interactions

  • Live vaccines — caution; IgE suppression may affect immune response

Monitoring

  • UAS7 (urticaria activity score) response
  • Anaphylaxis observation (30 min post-injection)
  • Review at 12 weeks (discontinue if no response)
  • 6-monthly reassessment for continued prescription

Reference: BNFc; BNF 90; ASTERIA I (Maurer et al. NEJM 2013); ASTERIA II; GLACIAL trial; NICE TA339; MHRA SPC Xolair; EAACI/GA²LEN/EDF/WAO Urticaria Guidelines (2022). Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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