Florbetapir

Florbetapir (F-18) is a radiopharmaceutical used with positron emission tomography (PET) to estimate beta-amyloid neuritic plaque density in the living brain. It binds selectively to amyloid plaques, enabling PET imaging to visualize plaque distribution in the cortex of adults with cognitive impairment being evaluated for Alzheimer’s disease and other causes of cognitive decline.

The compound was developed by Avid Radiopharmaceuticals and is marketed as Amyvid following approval by the U.S. Food and Drug Administration in 2012. Florbetapir is administered intravenously, typically as about 370 MBq (10 mCi). PET imaging is performed roughly 50 to 70 minutes after injection, and the resulting images show cortical regions with amyloid deposition as increased radiotracer uptake.

Interpretation of the scans is contextual. A positive scan indicates substantial amyloid plaque deposition in the cortex, which can support a diagnosis in the appropriate clinical setting. A negative scan makes significant amyloid pathology unlikely. However, amyloid positivity can occur in individuals with other neurological conditions and in some asymptomatic older adults, and not all cognitive impairment is due to amyloid pathology. Florbetapir imaging is intended to aid diagnosis and should be integrated with clinical assessment and other diagnostic information.

Safety and practical considerations include its relatively short physical half-life (about 110 minutes) and the use of ionizing radiation. Typical radiation exposure is within the range for PET tracers. Adverse reactions are uncommon. It should be used with caution in pregnancy and lactation, and interpretation requires correlation with clinical findings.