GLOFIL-125

GLOFIL-125- iothalamate sodium, i-125 injection
QOL Medical

DESCRIPTION

General

GLOFIL® -125 (Sodium Iothalamate I-125 Injection) is a sterile, nonpyrogenic aqueous injection containing approximately 1 mg sodium iothalamate per mL, and 0.9 percent benzyl alcohol as a preservative. The radioactive concentration of the material is 250-300 μCi/mL as of the calibration date. Sodium bicarbonate and hydrochloric acid are present for pH adjustment.

Physical Characteristics

Iodine-125 decays by electron capture with a physical half-life of 60.14 days. Photons that are useful for detection are listed in Table 1.

Table 1. Principal Radiation Emission Data *
*
ICRP Publication 38: Radionuclide Transformations — Energy and Intensity of Emissions. Published for the International Commission on Radiological Protection by Pergamon Press, New York, 1983, p. 446.
Radiation Mean Number Per Disintegration Mean Energy (keV)
Gamma-1 0.067 35.5
1 X-ray 0.741 27.5
2 X-ray 0.398 27.2
1 X-ray 0.140 31.0
2 X-ray 0.043 31.7
3 X-ray 0.072 30.9

The specific gamma ray constant for I-125 is 1.43 R/mCi-hr at 1 cm. The first half value thickness of lead (Pb) for I-125 is 0.017 mm. A range of values for the relative attenuation of the radiation emitted by this radionuclide resulting from interposition of various thicknesses of Pb is shown in Table 2. For example, the use of 0.28 mm of Pb will decrease the external radiation exposure by a factor of 10,000.

Table 2. Radiation Attenuation by Lead Shielding *
*
Data supplied by Oak Ridge Associated Universities, Radiopharmaceutical Internal Dose Information Center, Oak Ridge, TN 1989.
Shield Thickness (Pb), mm Coefficient of Attenuation
0.017 0.5
0.058 0.1
0.12 0.01
0.2 0.001
0.28 0.0001

To correct for physical decay of this radionuclide, the fractions that remain at selected time intervals after the date of calibration are shown in Table 3.

Table 3. Physical Decay Chart; I-125, half-life 60.14 days
*
Calibration Date
Days Fraction Remaining Days Fraction Remaining Days Fraction Remaining
0* 1.000 15 0.841 30 0.707
1 0.989 16 0.831 31 0.699
2 0.977 17 0.822 32 0.691
3 0.966 18 0.812 33 0.683
4 0.955 19 0.803 34 0.675
5 0.944 20 0.794 35 0.667
6 0.933 21 0.785 36 0.660
7 0.922 22 0.776 37 0.652
8 0.912 23 0.767 38 0.645
9 0.901 24 0.758 39 0.637
10 0.891 25 0.749 40 0.630
11 0.881 26 0.740 41 0.623
12 0.871 27 0.732 42 0.616
13 0.861 28 0.724 43 0.608
14 0.851 29 0.715 44 0.601
45 0.595
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