Sodium Iodide I 131 Diagnostic Recall
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Questions & Answers
Side Effects & Adverse Reactions
The recent intake of stable iodine in any form, or the use of thyroid or anti-thyroid drugs will affect the uptake of radioiodide. Accordingly, the patient should be questioned carefully regarding previous medication and procedures involving radiographic contrast media.
The calibration date and expiration date are indicated on the container label.
Radiopharmaceuticals should be used only by nuclear physicians and/or radiopharmacists who are qualified by training and experience in the safe use and handling of radionuclides, and whose experience and training have been approved by the appropriate governmental agency authorized to license the use of radionuclides. (See Drug Handling section.)
As in the use of any radioactive material, care should be taken to minimize radiation exposure to the patient consistent with proper patient management and to assure minimum radiation exposure to occupational workers.
Carcinogenesis, Mutagenesis, Impairment of Fertility
No long-term animal studies have been performed to evaluate carcinogenic potential, mutagenic potential, or whether this drug affects fertility in males or females.
Pregnancy Category X
See CONTRAINDICATIONS section.
Radioiodine is excreted in human milk during lactation. Therefore, formula feedings should be substituted for breast feedings.
Safety and efficacy in pediatric patients have not been established.
Adequate and well controlled studies on the relationship of age to the effect of radioiodide have not been performed in geriatric population.
This drug is known to be substantially excreted by the kidney and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection and it may be useful to monitor renal function.
There is currently no legal information available for this drug.
FDA Safety Alerts
There are currently no FDA safety alerts available for this drug.
There is currently no manufacturer warning information available for this drug.
FDA Labeling Changes
There are currently no FDA labeling changes available for this drug.
Sodium Iodide I-131 is indicated for use in performance of the radioactive iodide (RAI) uptake test to evaluate thyroid function. Diagnostic doses may also be employed in localizing metastases associated with thyroid malignancies.
There is currently no drug history available for this drug.
Sodium Iodide I 131 Capsule USP for diagnostic use is a radiopharmaceutical containing Sodium Iodide I-131 and supplied for oral administration in a gelatin capsule. Each capsule contains no-carrier-added Sodium Iodide I-131, Disodium Edetate Dihydrate USP as a stabilizer, Sodium Thiosulfate Pentahydrate USP as a reducing agent, and Dibasic Sodium Phosphate Anhydrous USP.
Sodium Iodide I 131 Capsule USP (Diagnostic - Oral) is available in 3.70 megabecquerels (100 microcuries) at time of calibration. Other activities of 2.03, 1.11, 0.61, and 0.33 megabecquerels (55, 30, 16.5, and 9 microcuries/capsule) are available by using the color-coded decay calendar provided or by calculation using the date and time of calibration.
Sodium Iodide I-131 is designated chemically as Na131I (MW 153.99, CAS 7681-72-5).
Iodine I-131 decays by beta emission and associated gamma emission with a physical half-life of 8.04 days.1 Photons that are useful for detection and imaging are listed in Table 1.
Principal Radiation Emission Data
|1 Kocher, David C., “Radioactive Decay Data Tables”, DOE/TIC-11026, (1981) p. 133.|
Mean % per Disintegration
Mean Energy (keV)
The specific gamma-ray constant for iodine I-131 is 15.8 µC•kg-1•MBq-1•hr-1 (2.27 R/mCi-hr) at 1 cm. The first half-value thickness of lead (Pb) for iodine I-131 is 0.24 cm. A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of Pb is shown in Table 2. For example, the use of 2.55 cm of Pb will decrease the external radiation exposure by a factor of about 1,000.
Radiation Attenuation by Lead Shielding
|Data supplied by Oak Ridge Associated Universities, Radiopharmaceutical Internal Dose Information Center, Oak Ridge TN, 1987.|
|Shield Thickness |
Coefficient of Attenuation
To correct for physical decay of iodine I-131, the fractions that remain at selected intervals after the time of calibration are shown in Table 3.
Physical Decay Chart: Iodine I-131, Half-Life 8.04 days
|* Calibration time|