Xenon

XENON- xenon, xe-133 gas
Bristol-Myers Squibb

DESCRIPTION:

XENON Xe 133 Gas is supplied in a mixture of xenon gas (5%) in carbon dioxide (95%). It is contained within septum sealed glass vials and is suitable for inhalation in the diagnostic evaluation of pulmonary function and imaging, as well as assessment of cerebral blood flow. Xenon Xe 133 Gas is reactor-produced as a by-product of Uranium U235 fission. Each vial contains the labeled amount of Xenon Xe 133 radioactivity at the time of calibration. The contents of the vial are in gaseous form, contain no preservatives, and are ready for use.

Xenon Xe 133 is chemically and physiologically related to elemental Xenon, a non-radioactive monoatomic gas which is physiologically inert except for anesthetic properties at high doses.

PHYSICAL CHARACTERISTICS

Xenon Xe 133 decays by beta and gamma emissions with a half-life of 5.245 days.1 Significant radiations which are emitted by the nuclide are listed in Table 1.

Table 1. Principal Radiation Emission Data from Xenon-133
Mean Mean % per
Radiation Energy (KeV) Disintegration
Beta-2 100.6 99.3
Ce-K-2 45.0 53.3
Ce-L-2 75.3 8.1
Ce-M-2 79.8 1.7
Gamma-2 81.0 36.5
Kα2 X-ray 30.6 13.6
Kα1 X-ray 31.0 25.3
Kβ X-ray 35.0 9.1

1
Kocher, David C., “Radioactive Decay Data Tables,” DOE/TIC-11026, p. 138,1981.

EXTERNAL RADIATION

The specific gamma ray constant for Xenon Xe 133 is 3.6 microcoulombs/Kg-MBq-hr (0.51R/hr-mCi) at 1 cm. The first half value thickness of lead is 0.0035 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 0.20 cm of Pb will decrease the external radiation exposure by a factor of 1,000.

Table 2. Radiation Attenuation by Lead Shielding
cm of Pb Radiation Attenuation Factor
0.0035 0.5
0.037 10-1
0.12 10-2
0.20 10-3
0.29 10-4

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

Table 3. Xenon Xe 133 Physical Decay Chart (Half Life 5.245 days)
Fraction Fraction
Day Remaining Day Remaining
*
Calibration Day
0* 1.000 8 .349
1 .877 9 .302
2 .768 10 .268
3 .674 11 .235
4 .591 12 .206
5 .518 13 .181
6 .452 14 .157
7 .398

CLINICAL PHARMACOLOGY:

Xenon Xe 133 is a readily diffusible gas which is neither utilized nor produced by the body. It passes through cell membranes and freely exchanges between blood and tissue. It tends to concentrate more in body fat than in blood, plasma, water or protein solutions. In the concentrations used for diagnostic purposes it is physiologically inactive. Inhaled Xenon Xe 133 Gas will enter the alveolar wall and enter the pulmonary venous circulation via the capillaries. Most of the Xenon Xe 133 that enters the circulation from a single breath is returned to the lungs and exhaled after a single pass through the peripheral circulation.

INDICATIONS AND USAGE:

Inhalation of Xenon Xe 133 Gas has proved valuable for the evaluation of pulmonary function and for imaging the lungs. It may also be applied to assessment of cerebral flow.

CONTRAINDICATIONS:

None known.

WARNINGS:

Xenon Xe 133 Gas delivery systems, i.e., respirators or spirometers, and associated tubing assemblies must be leakproof to avoid loss of radioactivity into the environs not specifically protected by exhaust systems.

Xenon Xe 133 adheres to some plastics and rubber and should not be allowed to stand in tubing or respirator containers. The unrecognized loss of radioactivity from the dose for administration may render the study non-diagnostic.

PRECAUTIONS:

General

Xenon Xe 133, 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. Also, care should be taken to minimize radiation exposure to patients consistent with proper patient management.

Exhaled Xenon Xe 133 gas should be controlled in a manner that is in compliance with the appropriate regulations of the government agency authorized to license the use of radionuclides.

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 or whether Xenon Xe 133 affects fertility in males or females.

Pregnancy Category C

Animal reproductive studies have not been conducted with Xenon Xe 133 Gas. It is also not known whether Xenon Xe 133 Gas can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Xenon Xe 133 Gas should be given to a pregnant woman only if clearly needed.

Ideally, examination using radiopharmaceuticals, especially those elective in nature in a woman of childbearing capability, should be performed during the first few (approximately 10) days following the onset of menses.

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