Sodium Fluoride F 18 (Page 2 of 3)

4 CONTRAINDICATIONS

None.

5 WARNINGS AND PRECAUTIONS

5.1 Allergic Reactions

As with any injectable drug product, allergic reactions and anaphylaxis may occur. Emergency resuscitation equipment and personnel should be immediately available.

5.2 Radiation Risks

Sodium Fluoride F 18 Injection, USP may increase the risk of cancer. Carcinogenic and mutagenic studies with Sodium Fluoride F 18 Injection, USP have not been performed. Use the smallest dose necessary for imaging and ensure safe handling to protect the patient and health care worker [see Dosage and Administration (2.1)].

6 ADVERSE REACTIONS

No adverse reactions have been reported for Sodium Fluoride F 18 Injection, USP based on a review of the published literature, publicly available reference sources, and adverse drug reaction reporting systems. However, the completeness of these sources is not known.

7 DRUG INTERACTIONS

The possibility of interactions of Sodium Fluoride F 18 Injection, USP with other drugs taken by patients undergoing PET imaging has not been studied.

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Pregnancy Category C
Any radiopharmaceutical including Sodium Fluoride F 18 Injection, USP has a potential to cause fetal harm. The likelihood of fetal harm depends on the stage of fetal development, and the radionuclide dose. Animal reproductive and developmental toxicity studies have not been conducted with Sodium Fluoride F 18 Injection, USP. Prior to the administration of Sodium Fluoride F 18 Injection, USP to women of childbearing potential, assess for presence of pregnancy. Sodium Fluoride F 18 Injection, USP should be given to a pregnant woman only if clearly needed.

8.3 Nursing Mothers

It is not known whether Sodium Fluoride F 18 Injection, USP is excreted into human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to interrupt nursing after administration of Sodium Fluoride F 18 Injection, USP or not to administer Sodium Fluoride F 18 Injection, USP, taking into account the importance of the drug to the mother. The body of scientific information related to radioactive decay, drug tissue distribution, and drug elimination shows that less than 0.01% of the radioactivity administered remains in the body after 24 hours (12 half-lives). To minimize the risks to a nursing infant, interrupt nursing for at least 24 hours.

8.4 Pediatric Use

In reported clinical experience in approximately 100 children, weight based doses (2.1 MBq/kg) ranging from 18.5 MBq-148 MBq (0.5 mCi-4 mCi) were used. Sodium Fluoride F 18 was shown to localize to areas of bone turnover including rapidly growing epiphyses in developing long bones. Children are more sensitive to radiation and may be at higher risk of cancer from Sodium Fluoride F 18 Injection, USP.

11 DESCRIPTION

11.1 Chemical Characteristics

Sodium Fluoride F 18 Injection, USP is a positron emitting radiopharmaceutical, containing no-carrier-added, radioactive fluoride F 18 that is used for diagnostic purposes in conjunction with PET imaging. It is administered by intravenous injection. The active ingredient, sodium fluoride F 18, has the molecular formula Na[18 F] with a molecular weight of 40.99, and has the following chemical structure:


Na+ 18 F

Sodium Fluoride F 18 Injection, USP is provided as a ready-to-use, isotonic, sterile, pyrogen-free, preservative-free, clear, and colorless solution. Each mL of the solution contains between 740 MBq to 22,200 MBq (20 mCi to 600 mCi) sodium fluoride F 18, at the EOS reference time, in 0.9% aqueous sodium chloride. The pH of the solution is between 4.5 and 8. The solution is presented in 25 mL multiple-dose glass vials with variable total volume and total radioactivity in each vial.

11.2 Physical Characteristics

Fluorine F 18 decays by positron (β+) emission and has a half-life of 109.7 minutes. Ninety-seven percent of the decay results in emission of a positron with a maximum energy of 633 keV and 3% of the decay results in electron capture with subsequent emission of characteristic X-rays of oxygen. The principal photons useful for diagnostic imaging are the 511 keV gamma photons, resulting from the interaction of the emitted positron with an electron (Table 2). Fluorine F 18 atom decays to stable 18 O-oxygen.

Table 2. Principal Emission Data for Fluoride F 18
Radiation/Emission % per Disintegration Mean Energy
Positron (β+) 96.73 249.8 keV
Gamma (±)* 193.46 511.0 keV

*Produced by positron annihilation[3] Kocher, D.C. Radioactive Decay Data Tables DOE/TIC-11026, 69, 1981.

The specific gamma ray constant for fluoride F 18 is 5.7 R/hr/mCi (1.35 x 10-6 Gy/hr/kBq) at 1 cm. The half-value layer (HVL) for the 511 keV photons is 4.1 mm lead (Pb). A range of values for the attenuation of radiation results from the interposition of various thickness of Pb. The range of attenuation coefficients for this radionuclide is shown in Table 3. For example, the interposition of an 8.3 mm thickness of Pb with a coefficient of attenuation of 0.25 will decrease the external radiation by 75%.

Table 3. Radiation Attenuation of 511 keV Photons by Lead (Pb) Shielding
Shield Thickness (Pb) mm Coefficient of Attenuation
0 0.00
4 0.50
8 0.25
13 0.10
26 0.01
39 0.001
52 0.0001

Table 4 lists the fraction of radioactivity remaining at selected time intervals from the calibration time. This information may be used to correct for physical decay of the radionuclide.

Table 4. Physical Decay Chart for Fluoride F 18
Time Since Calibration Fraction Remaining
0* 1.00
15 minutes 0.909
30 minutes 0.826
60 minutes 0.683
110 minutes 0.500
220 minutes 0.250
440 minutes 0.060
12 hours 0.011
24 hours 0.0001

*Calibration time

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Fluoride F 18 ion normally accumulates in the skeleton in an even fashion, with greater deposition in the axial skeleton (e.g. vertebrae and pelvis) than in the appendicular skeleton and greater deposition in the bones around joints than in the shafts of long bones.

12.2 Pharmacodynamics

Increased fluoride F 18 ion deposition in bone can occur in areas of increased osteogenic activity during growth, infection, malignancy (primary or metastatic) following trauma, or inflammation of bone.

12.3 Pharmacokinetics

After intravenous administration, fluoride F 18 ion is rapidly cleared from the plasma in a biexponential manner. The first phase has a half-life of 0.4 h, and the second phase has a half-life of 2.6 h. Essentially all the fluoride F 18 that is delivered to bone by the blood is retained in the bone. One hour after administration of fluoride F 18, only about 10% of the injected dose remains in the blood. Fluoride F 18 diffuses through capillaries into bone extracellular fluid space, where it becomes bound by chemisorption at the surface of bone crystals, preferentially at sites of newly mineralizing bone.

Deposition of fluoride F 18 in bone appears to be primarily a function of blood flow to the bone and the efficiency of the bone in extracting the fluoride F 18. Fluoride F 18 does not appear to be bound to serum proteins. In patients with normal renal function, 20% or more of the fluorine ion is cleared from the body in the urine within the first 2 hours after intravenous administration.

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