SODIUM IODIDE I-123: 50 Adverse Event Reports & Safety Profile

DESCRIPTION Sodium Iodide I 123 (Na 123 I) for diagnostic use is supplied in capsules for oral administration. The capsules are available in strengths of 3.7 and 7.4 megabecquerels (MBq) (100 and 200 μCi) I-123 at time of calibration. The radionuclidic composition at calibration is not less than 97.0 percent I-123, not more than 2.9 percent I-125 and not more than 0.1 percent Te-121. The radionuclidic composition at expiration time is not less than 87.2 percent I-123, not more than 12.4 percent I-125 and not more than 0.4 percent Te-121. The ratio of the concentration of I-123 and I-125 changes with time.

Graph

1 shows the minimum concentration of I-123 as a function of time and Graph 2 shows the maximum concentration of I-125 as a function of time.

Graph

1.

Radionuclidic

Concentration of I-123 PERCENT OF TOTAL RADIOACTIVITY: IODINE-123 Graph 2.

Radionuclidic

Concentration of I-125 PERCENT OF TOTAL RADIOACTIVITY: IODINE-125 Graph 1 Graph 2 Physical Characteristics Iodine-123 decays by electron capture with a physical half-life of 13.2 hours Kocher, David C., Radioactive Decay Data Tables. DOE/TIC-11026, 122 (1981). . The photon that is useful for detection and imaging studies is listed in Table 1.

Table

1.

Principal Radiation Emission Data Radiation

Mean % Disintegration Energy (keV) Gamma-2 83.4 159 External Radiation The specific gamma ray constant for I-123 is 1.6 R/hr-mCi at 1 cm. The first half-value thickness of lead (Pb) for I-123 is 0.005 cm. A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from the interposition of various thicknesses of Pb is shown in Table 2. For example, the use of 1.63 cm of lead will decrease the external radiation exposure by a factor of about 1,000.

Table

2.

Radiation

Attenuation by Lead Shielding Shield Thickness (Pb), cm Coefficient of Attenuation 0.005 0.10 0.88 1.63 2.48 0.5 10 -1 10 -2 10 -3 10 -4 Note that these estimates of attenuation do not take into consideration the presence of radionuclidic contaminants. To correct for physical decay of I-123, the fractions that remain at selected intervals after the time of calibration are shown in Table 3.

Table

3. Iodine I-123 Decay Chart: Half-Life

13.2 Hours Hours Fraction Remaining Hours Fraction Remaining *Time of Calibration 0* 3 6 9 12 15 1.000 0.854 0.730 0.623 0.533 0.455 18 21 24 27 30 0.389 0.332 0.284 0.242 0.207

INDICATIONS AND USAGE Administration of Sodium Iodide I 123 Capsules 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 * at 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 * Concentration at Time of Calibration: 97% I-123, 2.9% I-125, 0.1% Te-121 Concentration at Time of Expiry: 87.2% I-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 † Bladder voiding interval 4.8 hours. Bladder † 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)

CONTRAINDICATIONS To date there are no known contraindications to the use of Sodium Iodide I 123 Capsules.

ADVERSE REACTIONS Although rare, reactions associated with the administration of sodium iodide isotopes for diagnostic use include, in decreasing order of frequency, nausea, vomiting, chest pain, tachycardia, itching skin, rash and hives.

WARNINGS Females of childbearing age and pediatric patients should not be studied unless the benefits anticipated from the performance of the test outweigh the possible risk of exposure to the amount of ionizing radiation associated with the test.

PRECAUTIONS General The contents of the capsule are radioactive. Adequate shielding of the preparation must be maintained at all times. Do not use after the expiration time and date (30 hours after calibration time) stated on the label. The prescribed Sodium Iodide I 123 dose should be administered as soon as practical from the time of receipt of product (i.e., as close to calibration time as possible) in order to minimize the fraction of radiation exposure due to relative increase of radionuclidic contaminants with time.

Sodium

Iodide I 123, as well as other radioactive drugs, must be handled with care and appropriate safety measures should be used to minimize radiation exposure to clinical personnel. Care should also be taken to minimize radiation exposure to the patient consistent with proper patient management. Radiopharmaceuticals should be used only by physicians 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 government agency authorized to license the use of radionuclides. Carcinogenesis, Mutagenesis, Impairment of Fertility No long-term animal studies have been performed to evaluate carcinogenic potential, mutagenic potential, or whether Sodium Iodide I 123 affects fertility in males or females.

Pregnancy

Animal reproduction studies have not been conducted with this drug. It is also not known whether Sodium Iodide I 123 can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity.

Sodium

Iodide I 123 should be given to a pregnant woman only if clearly needed. Ideally examinations using radiopharmaceuticals, especially those elective in nature, in women of childbearing capability should be performed during the first few (approximately ten) days following the onset of menses.

Nursing Mothers

Since I 123 is excreted in human milk, formula-feeding should be substituted for breast-feeding if the agent must be administered to the mother during lactation.

Pediatric Use

Safety and effectiveness in children have not been established.