FLUORINE F-18
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FLUORINE F-18 (FLUORINE F-18).
Fluorine-18 decays by positron emission, and the emitted positron annihilates with an electron to produce two 511 keV gamma photons. When incorporated into radiopharmaceuticals such as fludeoxyglucose F-18, it accumulates in metabolically active tissues, enabling PET imaging.
| Metabolism | Fluorine-18 is not metabolized; it decays to oxygen-18 with a half-life of 109.7 minutes. |
| Excretion | Primarily renal; approximately 95% of administered activity is excreted in urine within 6 hours post-injection. Less than 5% is excreted in feces. |
| Half-life | Physiological half-life is 109.7 minutes (1.83 hours) for fluorine-18 decay by positron emission, with a physical half-life of 109.7 minutes. The biological half-life is dependent on the radiolabeled compound; for [18F]FDG, the effective half-life is approximately 3-4 hours. |
| Protein binding | For [18F]FDG, less than 5% bound to plasma proteins; binding is negligible. For other fluorine-18 compounds, binding varies (e.g., [18F]florbetapir ~90% bound). |
| Volume of Distribution | For [18F]FDG, the volume of distribution is approximately 0.5 L/kg, reflecting distribution into total body water and tissue uptake via glucose transporters. |
| Bioavailability | Intravenous administration only; bioavailability is 100% for IV route. Oral bioavailability is negligible due to rapid decay and gastrointestinal metabolism. |
| Onset of Action | For [18F]FDG as a diagnostic tracer, uptake in tissues begins immediately after intravenous injection, with peak cerebral uptake at 30-60 minutes. For therapeutic applications (e.g., [18F]FLT), onset is dependent on compound and route. |
| Duration of Action | For diagnostic imaging, the duration of detectable signal is approximately 2-3 hours post-injection, limited by physical decay and biological clearance. The effective imaging window is typically 30-90 minutes post-injection for [18F]FDG. |
2-10 mCi (74-370 MBq) intravenous bolus, single administration for PET imaging.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required; renal excretion is negligible. |
| Liver impairment | No dose adjustment required; hepatic metabolism is minimal. |
| Pediatric use | 0.1-0.2 mCi/kg (3.7-7.4 MBq/kg) intravenous, minimum 1 mCi (37 MBq). |
| Geriatric use | No specific adjustment; use same as adult dose. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FLUORINE F-18 (FLUORINE F-18).
| Breastfeeding | Breastfeeding should be interrupted for a period after administration of Fluorine-18 to minimize infant exposure to radioactivity. The specific interruption time depends on the half-life (110 minutes) and the administered activity. Typically, it is recommended to pump and discard breast milk for at least 4 hours after injection. The milk-to-plasma (M/P) ratio is not well-documented. |
| Teratogenic Risk | Fluorine-18 is a radioactive isotope used for diagnostic imaging. There is no evidence of teratogenicity in humans at diagnostic doses; however, fetal exposure to ionizing radiation may increase the risk of childhood cancer. The risk is highest during the first trimester when organogenesis occurs. Use during pregnancy should be limited to cases where the benefit outweighs the potential risk. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Known hypersensitivity to any component of the radiopharmaceutical."]
| Precautions | ["Radiation exposure risk; use only when benefits outweigh risks.","Pregnancy: consider alternative imaging if possible.","Lactation: advise breastfeeding cessation for a specified period."] |
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| Fetal Monitoring | No specific maternal monitoring beyond standard radiation safety precautions is required. Fetal monitoring is not routine for diagnostic doses. Inadvertent exposure during unrecognized pregnancy should be reported, but no dedicated fetal monitoring is indicated. |
| Fertility Effects | There is no known effect of Fluorine-18 on fertility at diagnostic doses. High doses of radiation can cause temporary or permanent infertility, but such doses are not used in diagnostic imaging. |