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Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

  • Bleeding gums
  • Bone pain
  • Chills
  • Constipation
  • Cough
  • Coughing up blood
  • Depressed mood
  • Difficulty breathing
  • Difficulty swallowing
  • Dizziness
  • Dry skin and hair
  • Fast heartbeat
  • Feeling cold
  • Fever or chills
  • Hair loss
  • Headache
  • Hives
  • Hoarseness or husky voice
  • Increased menstrual flow or vaginal bleeding
  • Itching
  • Large, hive-like swelling on face, eyelids, lips, tongue, throat, hands, legs, feet, sex organs
  • Lower back or side pain
  • Muscle cramps and stiffness
  • Noisy breathing
  • Nosebleeds
  • Painful or difficult urination
  • Pale skin
  • Paralysis
  • Pinpoint red spots on skin
  • Prolonged bleeding from cuts
  • Puffiness or swelling of the eyelids or around the eyes, face, lips or tongue
  • Red or dark brown urine
  • Red or black, tarry stools
  • Shortness of breath
  • Skin rash
  • Slowed heartbeat
  • Sore throat
  • Sores, ulcers, or white spots on lips or in mouth
  • Swollen glands
  • Tightness in chest
  • Troubled breathing with exertion
  • Unusual bleeding or bruising
  • Unusual tiredness or weakness
  • Weight gain
  • Or wheezing

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Abdominal pain or stomach pain
  • Acid or sour stomach
  • Belching
  • Blurred vision
  • Body aches or pain
  • Confusion
  • Congestion
  • Diarrhea or increased bowel movements
  • Difficult or labored breathing
  • Difficulty having a bowel movement (stool)
  • Difficulty in moving
  • Dryness or soreness of throat
  • Faintness or lightheadedness when getting up from a lying or sitting position
  • Feeling of warmth or heat
  • Flushing or redness of skin, especially on face and neck
  • Headache
  • Heartburn
  • Indigestion
  • Itching skin
  • Joint pain
  • Swollen joints; muscle aching or cramping; muscle pains or stiffness; difficulty in moving
  • Lack or loss of strength
  • Loose or liquid stools
  • Muscle pain or stiffness
  • Nausea or feeling of upset stomach or feeling like you may vomit
  • Pain in joints
  • Runny nose
  • Stomach discomfort, upset or pain
  • Sudden sweating
  • Swelling of hands, ankles, feet, or lower legs
  • Swollen joints
  • Tender, swollen glands in neck
  • Trouble in swallowing
  • Voice changes
  • Vomiting


It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly and to check for unwanted effects.

While you are being treated with tositumomab and iodine I 131 tositumomab, and after you stop treatment with it, do not have any immunizations (vaccinations) without your doctor’s approval. Tositumomab and iodine I 131 tositumomab may lower your body’s resistance and there is a chance you might get the infection the immunization is meant to prevent.

Patients should be informed of the risks of hypothyroidism and be advised to take thyroid blocking agents during treatment.

Tositumomab and iodine I 131 tositumomab can temporarily lower the number of white blood cells in your blood, increasing the chance of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting. If this occurs, there are certain precautions you can take, especially when your blood count is low, to reduce the risk of infection or bleeding:

  • Avoid people with infections. Check with your doctor immediately if you think you are getting an infection or if you get a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination.
  • Check with your doctor immediately if you notice any unusual bleeding or bruising; black, tarry stools; blood in urine or stools; or pinpoint red spots on your skin.
  • Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.
  • Do not touch your eyes or the inside of your nose unless you have just washed your hands and have not touched anything else in the meantime.
  • Be careful not to cut yourself when you are using sharp objects such as a safety razor or fingernail or toenail cutters.
  • Avoid sports or other situations where bruising or injury could occur.

Proper Use


The dose of this medicine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

Before Using

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of tositumomab and iodine I 131 tositumomab in children with use in other age groups.


Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults. Although there is no specific information comparing use of tositumomab and iodine I 131 tositumomab in the elderly with use in other age groups, this medicine is not expected to cause different side effects or problems in older people than it does in younger adults.


Pregnancy Category Explanation
All Trimesters X Studies in animals or pregnant women have demonstrated positive evidence of fetal abnormalities. This drug should not be used in women who are or may become pregnant because the risk clearly outweighs any possible benefit.


Studies in women breastfeeding have demonstrated harmful infant effects. An alternative to this medication should be prescribed or you should stop breastfeeding while using this medicine.

Drug Interactions

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.

Other Interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of tositumomab and iodine I 131 tositumomab. Make sure you tell your doctor if you have any other medical problems, or bone marrow problems.


Tositumomab and iodine I 131 tositumomab is a protein called a monoclonal antibody. It is used to treat a type of cancer called non-Hodgkin’s lymphoma.

Tositumomab and iodine I 131 tositumomab is to be administered only by or under the immediate supervision of your doctor.