Dosing and uses of Flutemetamol F-18 (Vizamyl)
Adult dosage forms and strengths
IV injection
- 150MBq/mL (4.05mCi/mL) of flutemetamol F 18)
Beta-Amyloid Plaque Estimation
Radioactive, adjunctive diagnostic agent for PET brain imaging to estimate beta-amyloid neuritic plaque density in adult patients with cognitive impairment who are being evaluated for Alzheimer Disease (AD) and other causes of cognitive decline
A negative scan indicates sparse to no neuritic plaques, and is inconsistent with a neuropathological diagnosis of AD as a cause of cognitive impairment; whereas, a positive scan indicates moderate-to-frequent amyloid neuritic plaques
Moderate-to-frequent amyloid plagues are found in patients with AD, but may also be present in with other types of neurologic conditions as well as older people with normal cognition
Dosage
- 185 megabecquerels (MBq ), ie 5 millicuries (mCi) IV bolus administered within 40 seconds
- Follow injection with an IV flush of 5-15 mL of 0.9% NaCl
Image Display & Interpretation
A 20-minute PET image should be acquired starting 90 minutes after IV injection
The patient should be supine; position head to center the brain, including the cerebellum, in the PET scanner field of view
Reduce head movement with tape or other flexible head restraints may be employed
Display
- Display images with all planes (axial, sagittal, coronal planes) linked by crosshairs
- Select a color scale that provides a progression of low through high intensity (eg, rainbow or Sokoloff) to 1) provide colors that allow the reader to discriminate intensity levels above and below the intensity level of the pons, 2) provide a color for regions with little or no amyloid binding (eg, cerebellar cortex), and 3) provide a range of at least 5 distinct colors above 50-60% of the peak intensity
- Display the reference scale; adjust the color scale to set the pons to approximately 90% maximum intensity; cerebellar cortex should represent approximately 20-30% of peak intensity on both negative and positive scans
- Start image interpretation by displaying slices sequentially from the bottom of the brain to the top for the various brain regions with viewing planes designated in the prescribing information
Interpretation
- Image interpretation is based upon the distribution of radioactive signal within the brain; clinical information is not a component of the image assessment
- Images are designated as positive or negative by comparing the radioactivity in cortical gray matter with activity in the adjacent white matter; this determination is made only in the cerebral cortex; the signal uptake in the cerebellum does not contribute to the scan interpretation (for example, a positive scan may show retained cerebellar gray-white contrast even when the cortical gray-white contrast is lost)
- Negative scans show more radioactivity in white matter than in gray matter, creating clear gray-white contrast
- Positive scans show cortical areas with reduction or loss of the normally distinct gray-white contrast; these scans have one or more areas with increased cortical gray matter signal which results in reduced (or absent) gray-white contrast
- Specifically, a positive scan will have a) 2 or more brain areas (each larger than a single cortical gyrus) in which there is reduced or absent gray-white contrast; this is the most common appearance of a positive scan, b) 1 or more areas in which gray matter radioactivity is intense and clearly exceeds radioactivity in adjacent white matter, c) striatum intensity >50=60% of peak intensity
- See figures of PET images in the prescribing information for further information
Pediatric dosage forms and strengths
Safety and efficacy not established
Flutemetamol F-18 (Vizamyl) adverse (side) effects
1-10%
Flushing (2%)
Increased blood pressure (2%)
Headache (1%)
Nausea (1%)
Dizziness (1%)
Warnings
Contraindications
Contraindicated in patients with a history of hypersensitivity reaction, polysorbate 80, or any other inactive ingredient
Cautions
Hypersensitivity reactions (eg, flushing and dyspnea) have been observed within minutes following administration; these reactions may occur in patients with no history of prior exposure
Before initiating therapy, ask patients about prior reactions to drugs, especially those containing polysorbate
Resuscitation equipment and trained personnel should be immediately available
Risk for image misinterpretation
- Errors may occur in the estimation of brain neuritic plaque density during image interpretation; perform image interpretation independently of the patient’s clinical information
- Other errors may be due to extensive brain atrophy that limits the ability to distinguish gray and white matter on the scan as well as motion artifacts that distort the image
Radiation risk
- Similar to other radiopharmaceuticals, flutemetamol F 18 contributes to a patient’s overall long-term cumulative radiation exposure; long-term cumulative radiation exposure is associated with an increased risk of cancer
- Ensure safe handling to protect patients and health care workers from unintentional radiation exposure
Pregnancy and lactation
Pregnancy category: C; should be administered to a pregnant woman only if clearly needed; all radiopharmaceuticals have potential to cause fetal harm
The likelihood of fetal harm depends on the stage of fetal development and the magnitude of the radiopharmaceutical dose
Assess pregnancy status before administering to a female of reproductive potentia
Lactation: Unknown if distributed in human breast milk; avoid use in breastfeeding women or temporarily interrupt breastfeeding for 24 hr (>10 half-lives of radioactive decay for the F 18 isotope) after exposure
If breastfeeding is interrupted, the patient should pump and discard her breast milk and use alternate infant nutrition sources (eg, stored breast milk or infant formula) for 24 hr after administration
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Flutemetamol F-18 (Vizamyl)
Mechanism of action
Binds to beta-amyloid plaques and the F 18 isotope produces a positron signal that is detected by a PET scanner
In in vitro binding studies using postmortem human brain homogenates containing beta-amyloid plaques, the dissociation constant (Kd) for flutemetamol was 6.7 nm
Distribution
Rapidly distributed throughout body
The time-activity curves for flutemetamol F 18 in the brain of subjects with positive scans shows continual signal increases from time zero through 30 minutes post administration, with stable values thereafter up to at least 120 minutes post-injection
Elimination
Excretion: 37% renal; 52% hepatobiliary
Administration
IV Preparation
Must not be diluted
Inspect the radiopharmaceutical dose solution prior to administration and do not use it if it contains particulate matter or is discolored
Use aseptic technique and radiation shielding to withdraw solution
Assay the dose in a suitable dose calibrator prior to administration
Radiation safety
- Radioactive drug; handle with appropriate safety measures to minimize radiation exposure during administration
- Use waterproof gloves and effective shielding, including lead-glass syringe shields when handling
- Radiopharmaceuticals should only be used by or under the control of physicians who are qualified by specific training and experience in the safe use and handling of radioactive materials, and whose experience and training have been approved by the appropriate governmental agency authorized to license the use of radiopharmaceuticals
IV Administration
Inject through a short IV catheter (~1.5 inches or less) to minimize the potential for adsorption of the drug to the catheter
Portions of the dose may adhere to longer catheters
Administer as single IV bolus injection in a total volume of 10 mL or less; follow bolus injection with 5-15 mL of 0.9% NaCl IV flush
Storage
Store at 2-30ºC (36-86°F)
The product does not contain a preservative
Store within the original container or equivalent radiation shielding
This preparation is approved for use by persons under license by the Nuclear Regulatory Commission or the relevant regulatory authority of an Agreement State
