Omalizumab

💊 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. 🌬️

📖 About: Always check the BNF link here

• 📚 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)

⚖️ 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

• 📖 BNF: Omalizumab
• 💼 SmPC: Omalizumab (Xolair)
• Normansell R et al., *Cochrane Database Syst Rev* 2014; (1):CD003559.

💡 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.” 🚗💨