XENON XE 133
Clinical safety rating: caution
Comprehensive clinical and safety monograph for XENON XE 133 (XENON XE 133).
Xenon Xe 133 is a radioactive gas that emits gamma radiation. It is used as a tracer in pulmonary ventilation studies and regional cerebral blood flow measurements. The mechanism relies on its physical properties as an inert radioactive gas that diffuses across alveolar-capillary membranes and is distributed according to regional ventilation and perfusion.
| Metabolism | Xenon Xe 133 is inert and not metabolized; it is eliminated unchanged via exhalation. |
| Excretion | Primarily eliminated via exhalation through the lungs (>95% unchanged); minimal renal excretion (<5% as dissolved gas). |
| Half-life | Terminal elimination half-life: 1.5–2 minutes (fast washout from well-perfused tissues); total-body elimination half-life approximately 5–7 minutes due to slow release from adipose tissue. Clinical context: rapid clearance allows repeated imaging within short intervals. |
| Protein binding | Negligible (<5%); Xenon is a noble gas and does not bind appreciably to plasma proteins. |
| Volume of Distribution | Volume of distribution: 13–15 L/kg (large due to high lipid solubility, extensive distribution into fat and other tissues). Clinical meaning: indicates rapid and widespread tissue uptake, with adipose tissue as a slow-release reservoir. |
| Bioavailability | Inhalation: near 100% (gas is fully absorbed from alveoli into the bloodstream; intravenous injection not used clinically). |
| Onset of Action | Inhalation: immediate (seconds) as the gas reaches pulmonary alveoli and enters systemic circulation for brain/blood-flow imaging. |
| Duration of Action | Clinical effect (detectable radioactivity) lasts 5–10 minutes post-inhalation; imaging typically performed within first 2–3 minutes. Complete elimination within 1–2 hours from the body. |
5-10 mCi (185-370 MBq) inhaled or intravenously as a single dose for pulmonary ventilation/perfusion imaging.
| Dosage form | GAS |
| Renal impairment | No dose adjustment required; xenon is eliminated via exhalation. |
| Liver impairment | No dose adjustment required; xenon elimination is independent of hepatic function. |
| Pediatric use | 0.1-0.3 mCi/kg (3.7-11.1 MBq/kg) inhaled or intravenous, minimum 2 mCi (74 MBq), maximum 10 mCi (370 MBq). |
| Geriatric use | Use lowest effective dose; consider reduced respiratory function but no specific dose adjustment required. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for XENON XE 133 (XENON XE 133).
| Breastfeeding | No data on excretion in breast milk. Discontinue breastfeeding temporarily after administration. Advise pump and discard milk for at least 24 hours post-exposure. M/P ratio unknown. |
| Teratogenic Risk | Xenon Xe 133 is a radioactive gas used for diagnostic imaging. Limited data in pregnancy; radiation exposure carries risk of teratogenicity, especially during organogenesis (first trimester). Use only if benefit outweighs risk. Second and third trimester risk is lower but consider fetal radiation exposure. |
■ FDA Black Box Warning
None.
| Serious Effects |
None specifically documented; contraindicated in patients with known hypersensitivity to xenon or components.
| Precautions | ["Radiation exposure risk; minimize dose and duration.","Use with caution in patients with impaired pulmonary function.","Pregnancy category C; use only if benefit outweighs risk.","Lactation: discontinue nursing or drug.","Ensure adequate ventilation to prevent accumulation of exhaled gas."] |
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| Fetal Monitoring |
| Monitor maternal vital signs and radiation exposure. In pregnancy, assess fetal radiation dose; consider alternative imaging if possible. No specific fetal monitoring required. |
| Fertility Effects | No known direct effects on fertility. However, radiation exposure to gonads may theoretically affect future fertility; minimal with diagnostic doses. |