Side Effects of Xolair (Omalizumab) Injections Up to 5 Days Post-Administration
The most critical side effect to monitor within 5 days of Xolair injection is anaphylaxis, which can occur from immediately after injection up to 4 days later, though most reactions occur within the first 2 hours. 1
Timing-Specific Side Effects
Immediate to 2 Hours Post-Injection (Highest Risk Period)
Anaphylaxis is the most serious concern, occurring in approximately 0.09-0.2% of patients. 2 The reaction manifests with:
- Respiratory symptoms: wheezing, shortness of breath, cough, chest tightness, trouble breathing, throat tightness, hoarse voice 1
- Cardiovascular symptoms: low blood pressure, dizziness, fainting, rapid or weak heartbeat, anxiety, feeling of "impending doom" 1
- Dermatologic symptoms: flushing, itching, hives, feeling warm 1
- Oropharyngeal symptoms: swelling of throat or tongue, trouble swallowing 1
Analysis of 41 anaphylactic events showed that 61% (22/36) occurred within the first 2 hours after one of the first three doses. 2 Specifically:
- 16 reactions occurred within 30 minutes 2
- 7 reactions occurred between 30-60 minutes 2
- 5 reactions occurred between 1-2 hours 2
2-12 Hours Post-Injection
Five anaphylactic reactions occurred in this timeframe. 2 Delayed reactions included:
- Tongue swelling (particularly in patients on β-blockers) 2
- Lingual angioedema 2
- Increased asthma symptoms with urticaria 2
- Shortness of breath with watery, itchy eyes and throat closing sensation 2
Beyond 12 Hours to 5 Days Post-Injection
Three anaphylactic reactions occurred beyond 12 hours, with reactions documented up to 4 days after administration. 2, 1
A distinct constellation of serum sickness-like symptoms can develop 1-5 days after injection, including: 1
These symptoms may recur with subsequent doses and warrant discontinuation of Xolair. 1
Common Non-Life-Threatening Side Effects (Throughout 5-Day Period)
The following adverse events occur with similar frequency to placebo but should be monitored: 3, 4
- Injection site reactions 3, 4
- Viral infections 3, 4
- Upper respiratory tract infections 3, 4
- Sinusitis 3, 4
- Headache 3, 4
- Pharyngitis 3, 4
Special Populations and Considerations
Patients with diabetes mellitus may experience hyperglycemia requiring additional insulin, as each 150 mg vial contains 145.5 mg sucrose. 5 This can manifest within the 5-day window post-injection.
Critical Safety Monitoring
Patients must be observed for 2 hours after the first 3 injections and 30 minutes after subsequent injections, as this captures 75% of anaphylactic reactions. 2 However, all patients must carry an epinephrine autoinjector for the 24 hours following injection and be educated that reactions can occur up to 4 days later. 2, 1
Important caveat: The observation period recommendations are based on guideline analysis showing that extended monitoring beyond these timeframes in a clinical setting is impractical, but patients remain at risk for delayed reactions requiring self-treatment capability. 2