How to Prevent and Treat an Allergic Reaction to Rituxan

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An allergic reaction to Rituxan, also known as MabThera or Rituximab, is a common side effect of this drug that's used to treat lymphoma and other diseases. What are the signs of an allergic reaction and how is the reaction managed?

Rituxan is a monoclonal antibody, which means that it targets a specific molecule on white blood cells. The molecule, CD-20, plays a role in rheumatoid arthritis and certain types of cancer. Rituximab is indicated for treating non-Hodgkin’s lymphoma (NHL), chronic lymphocytic leukemia, rheumatoid arthritis, granulomatosis with polyangiitis (GPA), and microscopic polyangiitis (MPA).

A nurse taking care of a sick patient
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Rituximab contains a small amount of protein from mouse tissue. It is considered a "chimeric antibody," which means that it's made from components that come from two different species. While this is a crucial feature of its mechanism of action, our bodies are geared to recognize non-human proteins as foreign markers and potential invaders—and to start an immune reaction against them.

The allergic reaction from rituximab is generally a reaction to the mouse proteins in the drug.

Before rituximab is infused, you will likely be treated with medications that reduce the likelihood of an allergic reaction. This includes Tylenol (acetaminophen) and Benadryl (diphenhydramine) and sometimes steroid medications. Since diphenhydramine can make you sleepy, it's usually recommended that you have someone drive you home after your infusion.

Signs and Symptoms

The common signs of rituximab allergy are:

  • Fever and chills – these are the most common reactions and occur in most individuals
  • Nausea
  • Itching
  • Rash
  • Throat irritation or watering from the nose
  • Swelling of the hands, feet, or face
  • A drop in blood pressure
  • Dizziness
  • Spasm of the throat, similar to asthma
  • Headache

These allergic reactions, which occur during infusion, usually occur within 30 minutes to 2 hours of starting the drug infusion and do not begin after the infusion is complete.

Reactions are most likely to occur during the first infusion (nearly 80 percent of patients have a reaction) and tend to become less frequent with successive cycles.

Rarely, severe reactions may occur, including:

  • Severe breathing problems
  • Heart attack
  • A serious fall in blood pressure and shock


If you have a reaction, your healthcare provider will slow down or stop the infusion.

For some mild reactions, this is all that may be required. A number of drugs can be administered to reduce or stop the reaction. These include acetaminophen, antiallergics, IV saline, steroids, or drugs that raise blood pressure. In nearly all patients, the reaction can be controlled quickly with these measures.

For severe reactions, admission to the intensive care unit is necessary—with measures to maintain and monitor the blood pressure and breathing.

Though deaths have been reported from infusion reactions, they are extremely rare.


A few measures can prevent or reduce allergic reactions with rituximab:

  • Premedication: As noted above, you will probably be taking antihistamine medicines and steroids before the infusion.
  • Starting the infusion slowly: This is very important for the first infusion, when an allergic reaction is most likely. Infusions are routinely started slowly and the rate of infusion can be increased if a reaction does not occur.
  • Stopping blood pressure-lowering medication before infusions: Since a fall in blood pressure can occur during a reaction, your healthcare provider may advise you to stop using your antihypertensive medication before your infusion. You should only make this modification under specific guidance from your healthcare provider.

Those who have had a mild or moderate reaction with rituximab may be given the drug slowly and need to take precautions for subsequent treatments. Those who have severe reactions are usually not administered the drug anymore.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Levin AS, Otani IM, Lax T, Hochberg E, Banerji A. Reactions to Rituximab in an Outpatient Infusion Center: A 5-Year Review. The Journal of Allergy and Clinical Immunology: In Practice. 2017;5(1). doi:10.1016/j.jaip.2016.06.022

  2. Food and Drug Administration. Rituxan Package Insert.

  3. Kasi PM, Tawbi HA, Oddis CV, Kulkarni HS. Clinical review: Serious adverse events associated with the use of rituximab - a critical care perspective. Crit Care. 2012;16(4):231. doi:10.1186/cc11304

  4. John Hopkins Medicine. Rituxan.

Additional Reading

By Indranil Mallick, MD
 Indranil Mallick, MD, DNB, is a radiation oncologist with a special interest in lymphoma.