Patient-Specific Dosing for BEXXAR

Patient-specific dosing adjusts for patient-to-patient variations in clearance rate¹

Dosing for Iodine I 131 Tositumomab is based on individual patient pharmacokinetics (dosimetry) made possible by gamma emissions from Iodine-131
The goal of dosimetry is to administer the amount of radioactivity (mCi) required to consistently achieve a predetermined total body absorbed dose of radiation
- Doses are adjusted for platelet counts and obesity
The median blood clearance following administration of 485 mg of Tositumomab in 110 patients with non-Hodgkin’s lymphoma was 68.2 mg/hr (range: 30.2-260.8 mg/hr). Patients with high tumor burden, splenomegaly, or bone marrow involvement were noted to have a faster clearance, shorter terminal half-life, and larger volume of distribution
Total body clearance, as measured by total body gamma camera counts, was dependent on the same factors noted for blood clearance
Patients with rapid clearance required a higher treatment activity than those with slow clearance to deliver same total body absorbed dose (as illustrated below)

Adapted with permission from the Society of Nuclear Medicine from Seldin DW. Techniques for using BEXXAR for the treatment of non-Hodgkin’s lymphoma. J Nucl Med Technol. 2002;30:109-114.
Figure 3.⁴

These images are for illustrative purposes only. They are intended to represent the concept of patient-specific dosing and are not derived from actual data.

The elimination of Iodine-131 occurs by decay and excretion in the urine. After 5 days, the whole body clearance was 67% of the injected doses (n=49). Ninety-eight percent of the clearance was accounted for in the urine¹

Most patients receiving the BEXXAR therapeutic regimen can be released on the day of treatment

BEXXAR contains a radioactive component. Care should be taken, consistent with the institutional radiation safety practices and applicable federal guidelines, to minimize exposure of medical personnel and caregivers
According to the Nuclear Regulatory Commission (NRC) regulation code
10 CFR part 35.75, the BEXXAR therapeutic regimen can be administered as outpatient treatment (verify with local institutional guidelines)⁶
Patients will need to follow specific instructions for 1-2 weeks regarding⁷
- Radiation exposure to close personal contacts, children, and
pregnant women
- Travel on commercial transportation
- Personal hygiene
Following these simple instructions should keep family members’ and the public’s exposure below the threshold in the NRC regulations⁷

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Complete Prescribing Information for
BEXXAR (Tositumomab and Iodine I 131 Tositumomab)

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