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. |
| Molecular Weight | 133.3 |
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 | Xenon Xe 133 is a radiopharmaceutical. In the first trimester, fetal radiation exposure is associated with a risk of malformations and carcinogenesis. Use only if benefit clearly outweighs risk. |
| 2nd trimester | Second trimester use may expose fetus to ionizing radiation; risk of carcinogenesis persists. Use only if essential. |
| 3rd trimester | Third trimester: fetal risk of radiation exposure remains. Consider alternative diagnostic methods. |
Clinical note
Comprehensive clinical and safety monograph for XENON XE 133 (XENON XE 133).
| Placental transfer | Xenon Xe 133 crosses the placenta due to its lipophilic nature and small molecular size. Animal studies confirm placental transfer; human data limited but expected. |
| Breastfeeding | Xenon Xe 133 is excreted in breast milk. The American Academy of Pediatrics recommends temporary cessation of breastfeeding after administration. The effective dose to the nursing infant is variable; consult nuclear medicine guidelines. |
■ FDA Black Box Warning
None.
| Serious Effects |
Known hypersensitivity to xenonPregnancy (unless benefit outweighs risk)Breastfeeding (unless necessary and temporary cessation is possible)
| 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. |
| Food/Dietary | No food or drug interactions; no dietary restrictions required with Xenon Xe 133. |
| Clinical Pearls |
Loading safety data…
| Lactation Rating | L4 (Hazardous) |
| 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. |
| 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. |
| Xenon Xe 133 is a radiopharmaceutical gas used for pulmonary ventilation scintigraphy. Its short half-life (5.24 days) allows for serial studies with minimal radiation exposure. Ensure patient has not recently undergone other nuclear medicine studies to avoid interference. Administer via closed breathing system to prevent environmental contamination. Image acquisition typically during equilibrium and washout phases. Adverse effects are rare but include dizziness, headache, or metallic taste. |
| Patient Advice | This is a radioactive gas used to image lung function. · You will inhale the gas through a mouthpiece or mask while lying under a camera. · The amount of radiation is very low and considered safe. · No special precautions are needed after the test; you can resume normal activities. · Drink plenty of fluids after the test unless instructed otherwise. |