💊 About
Omalizumab is a recombinant DNA–derived humanized IgG1κ monoclonal antibody that binds selectively to free immunoglobulin E (IgE) in the circulation and interstitial fluid, and to the membrane-bound form (mIgE) on B lymphocytes.
By reducing free IgE levels, it downregulates IgE receptors (FcεRI) on mast cells and basophils, dampening allergic inflammation. 🌬️
- 📚 Check BNF or equivalent for up-to-date prescribing advice and dose tables.
- 🧬 Used in severe allergic asthma and chronic spontaneous urticaria unresponsive to antihistamines.
⚙️ Mode of Action
- 🧩 Binds circulating IgE and prevents it from attaching to mast cells and basophils, reducing allergen-triggered degranulation.
- ⬇️ Lowers serum IgE and downregulates FcεRI receptors, reducing airway inflammation and hypersensitivity.
- 🌿 Does not bind to IgE already bound to receptors-thus avoids acute histamine release.
📋 Indications
- 🌬️ Prophylaxis of severe persistent allergic asthma inadequately controlled with inhaled corticosteroids and long-acting β₂-agonists.
- 🌸 Add-on therapy for chronic spontaneous urticaria refractory to antihistamines.
💉 Dose Range (Check BNF or SPC)
| 📌 Name | 💊 Starting Dose | ⏱️ Frequency | 🚪 Route |
|---|
| Omalizumab (Asthma) |
Dose according to baseline serum IgE and body weight (see BNF/SmPC dosing chart) |
Every 2–4 weeks |
SC |
| Omalizumab (Chronic Spontaneous Urticaria) |
300 mg |
Every 4 weeks |
SC |
⚖️ Interactions
- 💊 No major pharmacokinetic interactions known.
- ⚠️ Effects on vaccination or immunotherapy may be theoretically altered-monitor immune response.
⚠️ Cautions
- 🧠 History of autoimmune disease or immune complex disorders.
- 🐛 Increased susceptibility to helminth infection - treat existing infection before starting therapy.
- 🏥 Observe patients for post-injection anaphylaxis (rare, may be delayed).
⛔ Contraindications
- 🚫 Hypersensitivity to omalizumab or excipients.
💥 Side Effects
- 🤕 Headache, fatigue, arthralgia.
- 😷 Viral and upper respiratory tract infections.
- 💉 Injection-site reactions (pain, redness, swelling, pruritus).
- 🔥 Rare: Eosinophilic granulomatosis with polyangiitis (Churg–Strauss).
- ⚠️ Hypersensitivity or anaphylaxis - can be delayed for hours or days.
🧠 Teaching Note
Omalizumab illustrates the principle of targeted immunotherapy - neutralising circulating IgE to suppress allergic pathways rather than non-specifically blocking histamine or inflammation.
In severe asthma, it reduces exacerbations and steroid dependence. 🫁
Remember: dose is weight- and IgE-dependent, and onset of benefit may take weeks.
📚 References
💡 Teaching tip:
Omalizumab = “anti-IgE antibody.”
Think of it as asthma’s biologic equivalent of a seatbelt - it doesn’t stop exposure, but prevents severe allergic “crashes.” 🚗💨
