Tositumomab
Trade Name:
Bexxar
Type of Drug:
Tositumomab is a monoclonal antibody that has a radioactive substance (iodine 131) attached to it. It belongs to the class called radioimmunotherapy agents.
How Drug Works:
The monoclonal antibody part of tositumomab is directed to the CD20 receptor located on B lymphocyte cells. This receptor is found on some normal lymphocytes and also lymphocytes that are cancerous, as in non-Hodgkin's lymphoma. The antibody attaches to the CD20 receptor and kills the cells by exposing the cell to radiation (iodine 131).
How Drug Is Given:
Tositumomab is given as an injection in a vein. Because it is radioactive, the dose depends on the time that it will stay in your body. To figure this out, a test taking 3 days is done before the treatment. About 1 week later, the treatment dose is given as 2 injections in a vein. The first shot (antibody) is given over 1 hour, then the second shot (antibody and radioactive iodine) is given 20 minutes later.
Read the following information. If you do not understand it or if any of it causes you special concern, check with your doctor.

Before taking this drug, tell your doctor:

  • If you are trying to become pregnant, are pregnant, or breastfeeding. This drug may cause birth defects if either the male or female is taking it at the time of conception or during pregnancy. Men and women who are taking this drug need to use some kind of birth control. However, do not use oral contraceptives ("the pill") without checking with your doctor.

  • If you think you may want to have children in the future. Many chemotherapy drugs can cause sterility.

  • If you have any of the following medical problems: chickenpox or exposure to chickenpox, gout, heart disease, congestive heart failure, shingles, kidney stones, liver disease, or other forms of cancer.

  • If you are taking any other prescription or over-the-counter drugs, including vitamins and herbals.
Should I avoid any other medicines, foods, alcohol, and/or activities?
Your prescription and nonprescription medicines may interact with other drugs, causing harm. Certain foods or alcohol can also interact with drug products. Never begin taking a new medicine"prescription or nonprescription"without asking your doctor or nurse if it will interact with alcohol, food, or other medicines. Some drug products can cause drowsiness and affect activities such as driving.
Precautions:
You will receive a small amount of radiation and you will need to follow special instructions to prevent other people near you from being exposed to radiation. You should sleep alone for at least the first night after the treatment. Your doctor will tell you if this should continue for more nights, depending on the dose. You will need to keep at least 3 feet between you and other people for at least 2 days. Stay away from pregnant women and children if possible for this time or keep at least 9 feet between you and the woman or child if absolutely necessary for short periods. You should avoid commercial transportation and long car trips with others for at least the first 2 days as explained to you by your nurse or doctor.
It is important to drink at least one 12 oz glass of fluid every hour during the day for the first 2 days after the treatment. This means that you drink at least 3 quarts of fluid each day.
Many people receiving the treatment get mild flu-like symptoms after the treatment, including fever, nausea, and tiredness. Talk with your doctor or nurse about taking medicine to prevent fever and nausea.
While you are being treated with tositumomab, and after you stop treatment, do not have any immunizations (vaccinations) without your doctor's okay. Try to avoid contact with people who have recently taken the oral polio vaccine and people with infections.
Tositumomab can lower your blood counts (white blood cells, red blood cells, platelets). Your doctor will check your blood counts before and after each treatment. The blood counts reach their lowest point about 6 weeks after your treatment.
Tositumomab can lower your white blood cell count, reaching the lowest point about 6 weeks after the treatment is given. This can increase your risk of getting an infection. Report fever, of 100.5¡F or higher, and signs of infection such as a productive cough or burning when you pass your urine.
Tositumomab can lower your platelet count. This can increase your risk of bleeding. DO NOT take any aspirin or aspirin-containing medicines. Report unusual bruising or bleeding, such as nosebleeds, bleeding when you brush your teeth, black, tarry stools, or heavy menstrual periods right away.
Rarely, you can have a severe allergic reaction to the monoclonal antibody. Your nurse or doctor will watch you very closely during the treatment.
You will also be given an iodine supplement by mouth during your treatments to block the I-131 effect on the thyroid gland.
Tell all the doctors, dentists, and pharmacists you visit that you are taking this drug.
  • Most of the following side effects probably will not occur.
  • Your doctor or nurse will want to discuss specific care instructions with you.
  • They can help you understand these side effects and help you deal with them.
Side Effects:
More Common Side Effects
  • Mild to moderate Òflu-likeÓ symptoms with fever, nausea, and weakness
  • Decreased white blood cell count with increased risk infection
  • Decreased platelet count with increased risk of bleeding
  • Decreased red blood cell count with increased risk of tiredness and anemia
Rare Side Effects
  • Severe allergic reaction with flushing, hives, difficulty breathing, decreased blood pressure, loss of skin color, and loss of consciousness
Side Effects / Symptoms of the Drug

Tell your doctor or nurse right away if you do not understand how to take care of yourself while receiving tositumomab.
Other side effects not listed above can also occur in some patients. Tell your doctor or nurse if you develop any problems.
FDA Approval: This drug is being studied for cancer treatment.