Administration of Sodium Iodide I-123 is indicated as a diagnostic procedure to be used in evaluating thyroid function and/or morphology.
DOSAGE AND ADMINISTRATION
The recommended oral dose for the average patient (70 kg) is 3.7 to 14.8 MBq (100 to 400 μCi). The lower part of the dosage range 3.7 MBq (100 μCi) is recommended for uptake studies alone, and the higher part 14.8 MBq (400 μCi) for thyroid imaging. The determination of I-123 concentration in the thyroid gland may be initiated at six hours after administering the dose and should be measured in accordance with standardized procedures.
The patient dose should be measured by a suitable radioactivity calibration system immediately prior to administration. The capsules can be utilized up to 30 hours after calibration time and date. Thereafter, discard the capsules in accordance with standard safety procedures. The user should wear waterproof gloves at all times when handling the capsules or container.
Radiation Dosimetry
The estimated absorbed radiation doses to several organs of an average patient (70 kg) from oral administration of the maximum dose of 14.8 MBq (400 μCi) of I-123 are shown in Table 4 for thyroid uptakes of 5, 15, and 25%. For comparison at these three values of thyroid uptake, the estimated radiation doses from doses of 3.7 MBq (100 μCi) I-131, also used as thyroid imaging agent, are also included.
Table 4. Absorbed Radiation Dose Estimates as a Function of Maximum Thyroid Uptake for Sodium Iodide I-123 1At Time of Calibration and Expiry Compared to Sodium Iodide I-131
Estimated Radiation Absorbed Doses
I-123 mGy/14.8 MBq (rads/400 μCi)
I-131 mGy/3.7 MBq (rads/100 μCi)
Target Organ
Maximum Thyroid Uptake (%)
TOC
TOE
1Concentration at Time of Calibration: 97% I-123, 2.9% I-125, 0.1% Te-121
Concentration at Time of Expiry: 87.2% 1-123, 12.4% I-125, 0.4% Te-121
Metabolic model in MIRD Dose Estimate Report 5 followed for I-123 and I-125
Metabolic model in ICRP 30 followed for Te-121
2 Bladder voiding interval 4.8 hours.
Bladder2
5
1.7 (0.17)
1.7 (0.17)
2.9 (0.29)
15
1.6 (0.16)
1.6 (0.16)
2.7 (0.27)
25
1.4 (0.14)
1.5 (0.15)
2.4 (0.24)
Stomach Wall
5
0.96 (0.096)
0.98 (0.098)
1.7 (0.17)
15
0.89 (0.089)
0.91 (0.091)
1.5 (0.15)
25
0.82 (0.082)
0.85 (0.085)
1.4 (0.14)
Small Intestine
5
0.70 (0.070)
0.71 (0.071)
1.2 (0.12)
15
0.65 (0.065)
0.67 (0.067)
1.1 (0.11)
25
0.60 (0.060)
0.62 (0.062)
0.99 (0.099)
Liver
5
0.089 (0.0089)
0.13 (0.013)
0.16 (0.016)
15
0.10 (0.010)
0.18 (0.018)
0.28 (0.028)
25
0.11 (0.011)
0.24 (0.024)
0.41 (0.041)
Ovaries
5
0.18 (0.018)
0.19 (0.019)
0.18 (0.018)
15
0.17 (0.017)
0.18 (0.018)
0.18 (0.018)
25
0.16 (0.016)
0.18 (0.018)
0.17 (0.017)
Skeleton
5
0.11 (0.011)
0.16 (0.016)
0.12 (0.012)
15
0.12 (0.012)
0.18 (0.018)
0.18 (0.018)
25
0.14 (0.014)
0.21 (0.021)
0.24 (0.024)
Red Marrow
5
0.12 (0.012)
0.16 (0.016)
0.15 (0.015)
15
0.12 (0.012)
0.18 (0.018)
0.21 (0.021)
25
0.13 (0.013)
0.19 (0.019)
0.27 (0.027)
Testes
5
0.076 (0.0076)
0.089 (0.0089)
0.12 (0.012)
15
0.072 (0.0072)
0.087 (0.0087)
0.12 (0.012)
25
0.068 (0.0068)
0.085 (0.0085)
0.12 (0.012)
Thyroid
5
25 (2.5)
75 (7.5)
260 (26)
15
77 (7.7)
230 (23)
780 (78)
25
130 (13)
410 (41)
1300 (130)
Total Body
5
0.11 (0.011)
0.16 (0.016)
0.24 (0.024)
15
0.14 (0.014)
0.25 (0.025)
0.47 (0.047)
25
0.17 (0.017)
0.35 (0.035)
0.70 (0.070)
HOW SUPPLIED
Catalog Number 601,602.
Sodium Iodide I-123 is supplied as capsules for oral administration in strengths of 3.7 MBq (100 μCi) (red and white) (NDC 0019-N601-10) and 7.4 MBq (200 μCi) (green and white) (NDC 0019-N602-20) at time of calibration. Each gelatin capsule contains sucrose as a filler. The capsules are packaged in plastic vials containing one capsule of a single strength per vial. The plastic vial is packaged in a lead shield. A package insert is supplied with each lead shield.
Storage and Handling
The contents of the vial are radioactive and adequate shielding and handling precautions must be maintained.
Dispense and preserve capsules in tightly-closed containers that are adequately shielded. Store at controlled room temperature 20° to 25°C (68° to 77°F).
Storage and disposal of Sodium Iodide I-123 Capsules should be controlled in a manner that is in compliance with the appropriate regulations of the government agency authorized to license the use of this radionuclide.