Headache, fever, chills, nausea, heartburn, flushing, weakness, or dizziness may occur. If any of these effects persist or worsen, contact your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including: back/joint/muscle pain, increased thirst/urination, swelling of the hands/feet, tingling of the hands/feet.

If you have a current or past infection with hepatitis B or other virus infections (e.g., herpes, JC virus), rituximab may infrequently cause the infection to return or worsen. This may happen during treatment or up to 1 year after treatment is finished. Very serious liver disease could occur. If you have hepatitis B, you may be given antiviral medications to control the disease. Get medical help right away if you develop signs of a new or returning infection or liver disease such as: persistent stomach/abdominal pain, extreme tiredness, dark urine, yellowing eyes/skin.

This medication can cause a decrease in blood cells (cytopenia), which can cause bleeding problems and lower the body's ability to fight an infection. This serious side effect can happen days, weeks, or months after your treatment has finished. Notify your doctor promptly if you develop any of the following side effects: easy bleeding/bruising, black/tarry stools, vomit that looks like coffee grounds, signs of an infection (e.g., fever, chills, persistent sore throat, painful urination).

A serious allergic reaction to this drug is unlikely, but get medical help right away if it occurs. Symptoms of a serious allergic reaction include: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the Rituxan (rituximab) Side Effects Center for a complete guide to possible side effects »

PRECAUTIONS: Before using rituximab, tell your doctor or pharmacist if you are allergic to it; or to other mouse protein medications; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: blood disorders (e.g., thrombocytopenia), heart problems (e.g., irregular heartbeat, angina), current or returning infections, lung problems (e.g., pulmonary infiltrates), previous severe reaction to monoclonal antibody treatment, planned surgery/vaccinations, virus infection (e.g., chickenpox, hepatitis B or C, herpes).

This drug may make you dizzy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Limit alcoholic beverages.

Before having surgery, tell your doctor or dentist that you are using this medication.

Do not have immunizations/vaccinations without the consent of your doctor, and avoid contact with people who have recently received oral polio vaccine or flu vaccine inhaled through the nose.

To lower your risk of getting cut, bruised, or injured, use caution with sharp objects like razors and nail cutters, and avoid activities such as contact sports.

Wash your hands well to prevent the spread of infections.

Caution should be used when using this in the elderly because they may be at greater risk for heart problems (e.g., irregular heartbeat) or lung problems (e.g., pneumonia).

During pregnancy, this medication must not be used unless clearly needed due to a risk of harm to the unborn baby. Discuss the risks and benefits with your doctor. Becoming pregnant is not recommended during treatment with this medication and for at least 12 months after treatment is finished. Consult your doctor or pharmacist about using a reliable form of birth control (e.g., condoms, birth control pills).

It is not known whether this drug passes into breast milk. Because of the possible risk to the infant, breast-feeding while using this drug is not recommended. You should not begin breast-feeding until treatment is finished and blood test show that there is no more rituximab in your body. Consult your doctor to decide when it is safe to start breast-feeding.