A 32-year-old woman with severe allergic asthma uncontrolled on high-dose inhaled corticosteroids has a total serum IgE of 350 IU/mL. Her physician plans therapy with omalizumab. Before calculating the dose, which two parameters must be known?
- A FEV1 percent predicted and exacerbation frequency
- B Blood eosinophil count and FeNO
- C Body weight and baseline serum IgE level ✓
- D Age and duration of asthma
Correct answer: C. Body weight and baseline serum IgE level
Explanation
Omalizumab is a humanised monoclonal antibody that binds free IgE at the FceRI-binding site (A-epsilon-3 domain), preventing IgE attachment to mast cells and basophils. Dosing tables are constructed from body weight and pretreatment total serum IgE, because the antibody is dosed to neutralise the circulating free IgE pool. Eosinophil counts guide anti-IL5 biologics such as mepolizumab, not omalizumab.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.