Bexxar

DRUG DESCRIPTION

The BEXXAR therapeutic regimen (Tositumomab and Iodine I 131 Tositumomab) is an anti-neoplastic radioimmunotherapeutic monoclonal antibody-based regimen composed of the monoclonal antibody, Tositumomab, and the radiolabeled monoclonal antibody, Iodine I 131 Tositumomab.

Tositumomab

Tositumomab is a murine IgG2a lambda monoclonal antibody directed against the CD20 antigen, which is found on the surface of normal and malignant B lymphocytes. Tositumomab is produced in an antibiotic-free culture of mammalian cells and is composed of two murine gamma 2a heavy chains of 451 amino acids each and two lambda light chains of 220 amino acids each. 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 liquid concentrate. It is supplied at a nominal concentration of 14 mg/mL Tositumomab in 35 mg and 225 mg single-use vials. The formulation contains 10% (w/v) maltose, 145 mM sodium chloride, 10 mM phosphate, and Water for Injection, USP. The pH is approximately 7.2.

Iodine I 131 Tositumomab

Iodine I 131 Tositumomab is a radio-iodinated derivative of Tositumomab that has been covalently linked to Iodine-131. Unbound radio-iodine and other reactants have been removed by chromatographic purification steps. Iodine I 131 Tositumomab is supplied as a sterile, clear, preservative-free liquid for IV administration. The dosimetric dosage form is supplied at nominal protein and activity concentrations of 0.1 mg/mL and 0.61 mCi/mL (at date of calibration), respectively. The therapeutic dosage form is supplied at nominal protein and activity concentrations of 1.1 mg/mL and 5.6 mCi/mL (at date of calibration), respectively. The formulation for the dosimetric and the therapeutic dosage forms contains 4.4%6.6% (w/v) povidone, 12 mg/mL maltose (dosimetric dose) or 915 mg/mL maltose (therapeutic dose), 8.59.5 mg/mL sodium chloride, and 0.91.3 mg/mL ascorbic acid. The pH is approximately 7.0.

BEXXAR (tositumomab and iodine 1131 tositumomab) Therapeutic Regimen

The BEXXAR (tositumomab and iodine 1131 tositumomab) therapeutic regimen is administered in two discrete steps: the dosimetric and therapeutic steps. Each step consists of a sequential infusion of Tositumomab followed by Iodine I 131 Tositumomab. The therapeutic step is administered 7-14 days after the dosimetric step. The BEXXAR (tositumomab and iodine 1131 tositumomab) therapeutic regimen is supplied in two distinct package configurations as follows:

BEXXAR (tositumomab and iodine 1131 tositumomab) Dosimetric Packaging
  • A carton containing two single-use 225 mg vials and one single-use 35 mg vial of Tositumomab supplied by McKesson BioServices and
  • A package containing a single-use vial of Iodine I 131 Tositumomab (0.61 mCi/mL at calibration), supplied by MDS Nordion.
BEXXAR (tositumomab and iodine 1131 tositumomab) Therapeutic Packaging
  • A carton containing two single-use 225 mg vials and one single-use 35 mg vial of Tositumomab, supplied by McKesson BioServices and
  • A package containing one or two single-use vials of Iodine I 131 Tositumomab (5.6 mCi/mL at calibration), supplied by MDS Nordion.

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 an energy of 364.5 keV (Ref 1).

External Radiation: The specific gamma ray constant for Iodine-131 is 2.2 R/millicurie hour at 1 cm. The first half-value layer is 0.24 cm lead (Pb) shielding. A range of values is shown in Table 1 for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of Pb. To facilitate control of the radiation exposure from this radionuclide, the use of a 2.55 cm thickness of Pb will attenuate the radiation emitted by a factor of about 1,000.

Table 1 - Radiation Attenuation by Lead Shielding

Shield Thickness
(Pb) cm
Attenuation
Factor
0.24 0.5
0.89 10-1
1.60 10-2
2.55 10-3
3.7 10-4

The fraction of Iodine-131 radioactivity that remains in the vial after the date of calibration is calculated as follows:

Fraction of remaining radioactivity of Iodine-131 after x days = 2-(x/8.04).

Physical decay is presented in Table 2.

Table 2 - Physical Decay Chart: Iodine-131: Half-Life 8.04 Days

Days Fraction Remaining
0* 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
*(Calibration day)

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

Some people receiving tositumomab have had a reaction to the infusion (when the medicine is injected into the vein). Tell your caregivers 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...

Read All Potential Side Effects and See Pictures of Bexxar


Bexxar Patient Information Including Side Effects

Brand Names: Bexxar Dosimetric, BexxarTherapeutic

Generic Name: tositumomab (Pronunciation: TOE si too MOE mab)

  • What is tositumomab (Bexxar)?
  • What are the possible side effects of tositumomab (Bexxar)?
  • What is the most important information I should know about tositumomab (Bexxar)?
  • What should I discuss with my health care provider before I receive tositumomab (Bexxar)?
  • How is tositumomab given (Bexxar)?
  • What happens if I miss a dose (Bexxar)?
  • What happens if I overdose (Bexxar)?
  • What should I avoid after receiving tositumomab (Bexxar)?
  • What other drugs will affect tositumomab (Bexxar)?
  • Where can I get more information?

What is tositumomab (Bexxar)?

Tositumomab is a monoclonal antibody that is linked with radioactive iodine I-131. Monoclonal antibodies are made to target and destroy only certain cells in the body. This may help to protect healthy cells from damage.

Tositumomab is used to treat certain forms of non-Hodgkin's lymphoma. It is usually given after other medications have been tried without successful treatment.

Tositumomab may also be used for other purposes not listed in this medication guide.

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

Some people receiving tositumomab have had a reaction to the infusion (when the medicine is injected into the vein). Tell your caregivers 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, easy bruising or bleeding, unusual weakness;
  • black, bloody, or tarry stools;
  • blood in your urine;
  • fever, chills, sore throat, body aches, flu symptoms;
  • cough with yellow or green mucus; or
  • stabbing chest pain, feeling short of breath.

Less serious side effects may include:

  • decreased energy;
  • weight gain;
  • headache;
  • joint or muscle pain;
  • feeling weak or irritable;
  • increased thirst and hot, dry skin;
  • nausea, vomiting, diarrhea, stomach pain;
  • loss of appetite;
  • mild itching or skin rash;
  • runny or stuffy nose; or
  • pain, itching, swelling, or redness around your IV needle.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.

What is the most important information I should know about tositumomab (Bexxar)?

You should not receive this medication if you are allergic to mouse proteins, or if you have ever had an allergic reaction to a monoclonal antibody.

Before you receive tositumomab, tell your doctor if you have kidney disease or severe bone marrow suppression.

Tositumomab can cause damage to the thyroid gland of an unborn baby if the mother receives this medication during pregnancy. You should not receive this medication if you are pregnant.

Tositumomab can be harmful to an unborn baby whether the father or the mother receives this medication at the time of conception. Use effective birth control to prevent pregnancy during your treatment, whether you are a man or a woman. Continue using birth control for at least 12 months after you have received tositumomab.

This medication can lower blood cells that help your body fight infections, making it easier for you to bleed from an injury or get sick from being around others who are ill. Avoid being near people who have colds, the flu, or other contagious illnesses. Contact your doctor at once if you develop signs of infection.

Do not receive a "live" vaccine just after you receive tositumomab.

After you are treated with tositumomab, your body will retain radioactive material for several days. During this time you will be giving off a small amount of radiation to others around you. Your caregivers should give you instructions about how to avoid exposing other people to radiation until this effect wears off. Follow these instructions carefully.

Take all medications your doctor prescribes to help protect your thyroid gland when you receive tositumomab. You may need to have blood tests to check your thyroid function at regular intervals for the rest of your life. Visit your doctor regularly.

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