Description
Xenon Xe-133 Gas is a carrier-free radioactive gas in air suitable for inhalation in pulmonary ventilation studies. Greater than 99.5% of the activity is Xe-133 with less than 0.01% of the activity associated with Iodine I-131. Pressure in the vial is less than atmospheric.
Pharmacology
Xenon Xe-133 Gas is a chemically inert and pharmacologically inactive gas at the concentrations used for diagnostic studies. It is neither a natural product of the body, nor is it utilized. Xenon Xe-133 Gas is readily diffusable, passing through cell membranes and exchanging between blood and tissue. It has limited solubility in aqueous media, exhibiting a preferential solubility in body fats over blood or plasma. Xenon Xe-133 Gas will cross the alveolar wall after inhalation, and will enter the venous circulation via the pulmonary capillary bed. Following a single breath, the majority of the Xenon Xe-133 Gas that enters the blood stream will be quickly returned to the lungs and will be exhaled. Xenon Xe-133 Gas is eliminated by the lungs into the expired air with a biological half-life of about 5 minutes.
Indications
Xenon Xe-133 Gas is indicated for the evaluation of pulmonary function and for imaging the lungs by means of inhalation studies. Inhalation of Xenon Xe-133 Gas may also be applied to the assessment of cerebral blood flow.
Contraindications
Hypersensitivity to this agent.
Warnings
Since adequate reproduction studies have not been performed in animals to determine whether this agent affects fertility in males or females, has teratogenic potential, or has other adverse effects on the fetus, this radiopharmaceutical preparation should not be administered to pregnant women unless it is considered that the benefits to be gained outweigh the potential hazards. It is not know if this agent is excreted in the human milk. Where an assessment of the risk/benefit ratio suggests the use of this product in lactating mothers, nursing should be
stopped. Ideally, examinations using radiopharmaceuticals in women of childbearing age, especially those of an elective nature, should be performed during the first few days (approximately 10) following the onset of menses.
Adequate studies do not exist to support the use of this radiopharmaceutical in pediatric patients. As in pregnancy and lactating mothers, the benefit to risk ratio should be assessed before consideration is given to the use of this product in this age group. Radiopharmaceuticals should only be used under the direction of, or by, physicians who
are qualified by specific training in the safe use and handling of radionuclides and whose training has been approved by the appropriate government agency authorized to license the use of radionuclides.
Precautions
In the use of any radioactive material, care should be taken to insure minimum radiation exposure to the patient, consistent with proper patient management, and to insure minimum radiation exposure to occupational workers. 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. Xenon Xe-133 Gas delivery systems, i.e., respirators or spirometers, and associated tubing assemblies must be leak-proof to avoid loss of radioactivity into the laboratory environs not specifically protected by exhaust systems. Xenon Xe-133 Gas adheres to some plastics and rubber and should not be allowed to stand in tubing or respirator containers, for such unrecognized loss of radioactivity from the dose for administration may render the study non-diagnostic.
Adverse Reactions
To date, no adverse reactions specifically attributable to the use of Xenon Xe-133 Gas have been reported.
Physical Characteristics
Xenon-133 is produced by fission of Uranium-235 and decays with a physical half-life of 5.245 days by beta emission to stable cesium-133.1 The 81.0 keV gamma ray listed in Table 1 is useful for detection in imaging studies.