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(tositumomab and iodine I 131 tositumomab)



Serious Allergic Reactions (Including Anaphylaxis): Serious, including fatal, allergicreactions have occurred during or following administration of the BEXXAR therapeuticregimen. Have medications for the treatment of allergic reactions available for immediateuse. Permanently discontinue the BEXXAR therapeutic regimen for serious allergicreactions and administer appropriate medical treatment [see WARNINGS AND PRECAUTIONS].

Prolonged and Severe Cytopenias: The BEXXAR therapeutic regimen resulted insevere and prolonged thrombocytopenia and neutropenia in more than 70% of the patientsin clinical studies. The BEXXAR therapeutic regimen should not be administered topatients with greater than 25% lymphoma marrow involvement, platelet count less than100,000 cells/mm³ or neutrophil count less than 1,500 cells/mm³ [see WARNINGS AND PRECAUTIONS, ADVERSE REACTIONS].

Radiation Exposure: The BEXXAR therapeutic regimen may be administered onlyunder the supervision of physicians who are certified under or participating in theBEXXAR therapeutic regimen certification program and who are authorized under the Radioactive Materials License at their clinical site. Follow institutional radiation safetypractices and applicable federal guidelines to minimize radiation exposure during handlingand after administration of the BEXXAR therapeutic regimen [see WARNINGS AND PRECAUTIONS].


The BEXXAR therapeutic regimen is composed of the monoclonal antibody tositumomab, and the radiolabeled monoclonal antibody, I-131 tositumomab.

Tositumomab is a murine IgG2a lambda monoclonal antibody directed against the CD20 antigen, produced in mammalian cells. The approximate molecular weight of tositumomab is 150 kD.

Tositumomab is supplied as a sterile, pyrogen-free, clear to opalescent, colorless to slightly yellow, preservative-free solution that must be diluted before intravenous administration. The formulation contains 100 mg/mL maltose, 8.5 mg/mL sodium chloride, 1 mg/mL phosphate, 1 mg/mL potassium hydroxide, and Water for Injection, USP. The pH is approximately 7.2.

I-131 tositumomab is tositumomab covalently linked to Iodine-131. I-131 tositumomab is supplied as a sterile, clear, preservative-free liquid. The formulation for I-131 tositumomab contains 0.9 to 1.3 mg/mL ascorbic acid, 1 to 2 mg/mL maltose (dosimetric dose) or 9 to 15 mg/mL maltose (therapeutic dose), 4.4% to 6.6% (w/v) povidone, and 8.5 to 9.5 mg/mL sodium chloride. The pH is approximately 7.0.

Physical/Radiochemical Characteristics of Iodine-131

Iodine-131 decays with beta and gamma emissions with a physical half-life of 8.04 days. The principal beta emission has a mean energy of 191.6 keV, and the principal gamma emission has energy of 364.5 keV.

External Radiation

The specific gamma ray constant for Iodine-131 is 2.2 R/millicurie hour at 1 cm. Use a 2.55 cm thickness of Pb (to attenuate the radiation emitted by a factor of about 1,000) to minimize radiation exposure from this radionuclide.

The fraction of Iodine-131 radioactivity that remains in the vial x days after the date of calibration is 2-(x/8.04).

Physical decay is presented in Table 5.

Table 5: Physical Decay Chart: Iodine-131: Half-Life 8.04 Days

Days Fraction Remaining
0a 1.000
1 0.917
2 0.842
3 0.772
4 0.708
5 0.650
6 0.596
7 0.547
8 0.502
9 0.460
10 0.422
11 0.387
12 0.355
13 0.326
14 0.299
a Calibration day.

What are the possible side effects of tositumomab (Bexxar Dosimetric, BexxarTherapeutic)?

Some people receiving a tositumomab injection have had a reaction to the infusion (when the medicine is injected into the vein). Tell your caregiver right away if you feel dizzy, nauseated, light-headed, sweaty, or short of breath, or if you have fever or chills during the injection.

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

  • pale skin, feeling...

Read All Potential Side Effects and See Pictures of Bexxar »

Last reviewed on RxList: 9/27/2012
This monograph has been modified to include the generic and brand name in many instances.

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