Sodium Iodide I 131 Diagnostic
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Questions & Answers
Side Effects & Adverse Reactions
None.
PRECAUTIONS
General
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.
Nursing Mothers
Radioiodine is excreted in human milk during lactation. Therefore, formula feedings should be substituted for breast feedings.
Pediatric Use
Safety and efficacy in pediatric patients have not been established.
Geriatric Use
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.
Legal Issues
There is currently no legal information available for this drug.
FDA Safety Alerts
There are currently no FDA safety alerts available for this drug.
Manufacturer Warnings
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.
Uses
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.
History
There is currently no drug history available for this drug.
Other Information
DESCRIPTION
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.
Table 1
Principal Radiation Emission Data
| 1 Kocher, David C., “Radioactive Decay Data Tables”, DOE/TIC-11026, (1981) p. 133. | ||
| Radiation |
Mean % per Disintegration |
Mean Energy (keV) |
| Beta-1 Beta-3 Beta-4 Gamma-7 Gamma-14 Gamma-17 |
2.12 7.36 89.3 6.05 81.2 7.26 |
69.4 96.6 191.6 284.3 364.5 637.0 |
EXTERNAL RADIATION
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.
Table 2
Radiation Attenuation by Lead Shielding
| Data supplied by Oak Ridge Associated Universities, Radiopharmaceutical Internal Dose Information Center, Oak Ridge TN, 1987. | |
| Shield Thickness (Pb) cm |
Coefficient of Attenuation |
| 0.24 0.89 1.6 2.55 3.73 |
0.5 10-1 10-2 10-3 10-4 |
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.
Table 3
Physical Decay Chart: Iodine I-131, Half-Life 8.04 days
| * Calibration time | |||||
| Days |
Fraction Remaining |
Days |
Fraction Remaining |
Days |
Fraction Remaining |
| 0* 1 2 3 4 5 6 7 8 9 10 |
1.000 .918 .842 .773 .709 .651 .597 .548 .503 .461 .423 |
11 12 13 14 15 16 17 18 19 20 21 |
.388 .356 .327 .300 .275 .253 .232 .213 .195 .179 .164 |
22 23 24 25 26 27 28 29 30
|
.151 .138 .127 .116 .107 .098 .090 .083 .076
|
Sources
Sodium Iodide I 131 Diagnostic Manufacturers
-
Jubilant Draximage Inc.
![Sodium Iodide I 131 Diagnostic (Sodium Iodide I 131) Capsule [Jubilant Draximage Inc.]](/wp-content/themes/bootstrap/assets/img/loading2.gif)
Sodium Iodide I 131 Diagnostic | Jubilant Draximage Inc.
The suggested oral dosage ranges employed in the average patient (70 kg) for diagnostic procedures for thyroid function are as follows:
Thyroid Uptake:
0.185 to 0.555 megabecquerels (5 to 15 microcuries)
Scintiscanning:
1.85 to 3.70 megabecquerels (50 to 100 microcuries)
Localization of Extra-Thyroidal Metastases:
37 megabecquerels (1,000 microcuries).
General Dosing Information
Patients should be adequately hydrated before and after administration of radioiodide to assure rapid urinary elimination of the iodide that is not absorbed by the thyroid gland.
Radition Dosimetry
The estimated absorbed radiation doses to an average (70 kg) euthyroid (normal functioning thyroid) patient from an oral dose of 3.70 megabecquerels (100 microcuries) of iodine I-131 are shown in Table 4.Table 4
MIRD DOSE ESTIMATE REPORT No. 5. Summary of Current Radiation Dose Estimates to Humans from I123 , I124, I125, I126, I130, I131 and I132 Sodium Iodide. J. Nucl. Med., 16, No. 9, 857-60 (1975).
Estimated Absorbed Radiation Doses from
an Oral Dose of 3.70 megabecquerels (100 microcuries)Tissue
Absorbed radiation doses for 3.70 megabecquerels
(100 microcuries)
Thyroid Uptake
5 %
15 %
25 %
mGy
rads
mGy
rads
mGy
rads
Thyroid
260
26.0
800
80.0
1300
130.0
Stomach wall
1.7
0.17
1.6
0.16
1.4
0.14
Red marrow
0.14
0.014
0.20
0.020
0.26
0.026
Liver
0.20
0.020
0.35
0.035
0.48
0.048
Testes
0.08
0.008
0.09
0.009
0.09
0.009
Ovaries
0.14
0.014
0.14
0.014
0.14
0.014
Total body
0.24
0.024
0.47
0.047
0.71
0.071
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