A 29-year-old woman has chronic spontaneous urticaria with daily wheals despite up-dosed second-generation antihistamines (four times the standard dose). She is started on omalizumab. The appropriate maintenance dosing schedule is:

• A 300 mg intramuscularly every 8 weeks
• B 300 mg subcutaneously once monthly for 6 months, then stop permanently
• C Weight-adjusted dosing every 2 weeks based on serum IgE
• D 150 mg or 300 mg subcutaneously every 4 weeks ✓

Explanation

Omalizumab, a humanized monoclonal antibody that binds free IgE, is licensed for chronic spontaneous urticaria inadequately controlled on H1 antihistamines. In urticaria the dose is a fixed 150 mg or 300 mg subcutaneous injection every 4 weeks, unlike asthma where dosing is weight- and IgE-adjusted. It is given subcutaneously, never intramuscularly, and treatment continues while clinically indicated rather than being stopped at a fixed time point.

Reference: Rook's Textbook of Dermatology, 9th ed.

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Written and medically reviewed by the StethoPrep medical team.