"Today, the U.S. Food and Drug Administration issued a proposal designed to assist companies developing new treatments for patients in the early stages of Alzheimer's disease, before the onset of noticeable (overt) dementia.
(Florbetapir F 18 Injection)
Amyvid contains florbetapir F 18, a molecular imaging agent that binds to β-amyloid aggregates, and is intended for use with PET imaging of the brain. Chemically, florbetapir F 18 is described as (E)-4-(2-(6-(2-(2-(2[18F] fluoroethoxy)ethoxy)ethoxy)pyridine3-yl)vinyl)-N-methylbenzamine. The molecular weight is 359 and the structural formula is:
Amyvid is a sterile, non-pyrogenic radioactive diagnostic agent for intravenous injection. The clear, colorless solution is supplied ready to use and each milliliter contains 0.1 to 19 micrograms of florbetapir and 500 - 1900 MBq (13.5 - 51 mCi) florbetapir F 18 at EOS, with 4.5 mg sodium ascorbate USP, and 0.1 mL dehydrated alcohol USP in 0.9% sodium chloride injection USP. The pH of the solution is between 5.5 and 7.5.
Amyvid is radiolabeled with [18F] fluorine (F 18) that decays by positron (β+) emission to O 18 and has a half-life of 109.77 minutes. The principal photons useful for diagnostic imaging are the coincident pair of 511 keV gamma photons, resulting from the interaction of the emitted positron with an electron (Table 3).
Table 3: Principal Radiation
Produced from Decay of Fluorine 18
|Radiation||Energy Level (keV)||Abundance (%)|
The point source air-kerma coefficienta for F-18 is 3.74E -17 Gy m²/(Bq s); this coefficient was formerly defined as the specific gamma-ray constant of 5.7 R/hr/mCi at 1 cm. The first half-value thickness of lead (Pb) for F 18 gamma rays is approximately 6 mmb. The relative reduction of radiation emitted by F-18 that results from various thicknesses of lead shielding is shown in Table 4. The use of ~8 cm of Pb will decrease the radiation transmission (i.e., exposure) by a factor of about 10,000.
Table 4: Radiation Attenuation of 511 keV Gamma Rays by Lead Shielding
|Shield Thickness cm of lead (Pb)||Coefficient of Attenuation|
aEckerman KF and A Endo. MIRD: Radionuclide Data and Decay
Schemes, 2nd Edition, 2008.
b Derived from data in NCRP Report No. 49. 1998, Appendix C
Last reviewed on RxList: 4/16/2012
This monograph has been modified to include the generic and brand name in many instances.
Additional Amyvid Information
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