fluorodeoxyphenylalanine 18F-DOPA (Rx)

Postmarketing Reports

General disorders and administration site conditions: Pain

Contraindications

None

Cautions

Use contributes to a patient’s overall long-term radiation exposure, which is associated with an increased risk of cancer; use smallest dose necessary for imaging and ensure safe handling to protect the patient and healthcare worker

Drug interaction overview

• Aromatic L-amino acid decarboxylase (AADC) inhibitors

  • Use of AADC inhibitors (eg, carbidopa, benserazide) may increase fluorodeoxyphenylalanine 18F-DOPA bioavailability to the brain by inhibiting peripheral decarboxylase activity and restricting peripheral metabolism
  • This interaction is beneficially used as part of the imaging procedure

• Drugs for treating Parkinson disease

  • Dopamine agonists, dopamine reuptake inhibitors, dopamine-releasing agents (DRAs), peripheral catechol-O-methyltransferase (COMT) inhibitors, and monoamine oxidase (MAO) inhibitors
  • Whether discontinuation of these drugs prior to fluorodeoxyphenylalanine 18F-DOPA administration may minimize the interference with an image is not fully known; however, if use of these drugs can be safely suspended, discontinue use 12 hr before the imaging study

Pregnancy

There are no available data on use in pregnant women

Additionally, animal reproductive and developmental toxicity studies have not been conducted

All radiopharmaceuticals have potential to cause fetal harm depending on the stage of fetal development and the magnitude of the radiation dose

Lactation

No data are available regarding the presence in human milk, the effects of the drug on the breastfed child, or on milk production

Minimize exposure to infant by temporarily discontinuing breastfeeding

Advise lactating women to pump and discard breastmilk for at least 24 hr (12 half-lives) 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.

Mechanism of Action

In dopaminergic nerve terminals in the brain, fluorodeoxyphenylalanine 18F-DOPA is decarboxylated by amino acid decarboxylase to fluorodopamine (FDA) F 18 and stored in presynaptic vesicles in the brain

Accumulation of F 18 FDA in the striatum is visually detected in the PET scan

Distribution

Distribution biological half-life (cleared from blood): 1-3 hr

Metabolism

Decarboxylated by aromatic amino acid decarboxylase in the striatum to fluorodopamine (FDA) F 18

FDA F 18 is also metabolized via monoamine oxidase to yield [18F] 6-fluoro-3,4-dihydroxyphenylacetic acid (18FDOPAC) and subsequently by COMT to yield [18F]6-fluorohomovanillic acid (18FHVA)

Elimination

Cleared from blood and tissue within 24 hr

Excretion: 80% urine

IV Preparation

Use aseptic techniques and radiation shielding during all operations involved in manipulation and administration

Calculate necessary volume to administer based on calibration time and dose

Inspect visually and do not use the drug if the solution contains particulate matter or is discolored

Measure the patient dose immediately prior to administration in a dose calibrator

Dispose of unused drug in compliance with applicable regulations

Patient preparation

• Hydration

  • NPO (except water) x4 hr before administrating drug
  • Minimize radiation absorbed dose to the bladder by instructing patient to hydrate (water only) before PET study and afterwards; also, void 70 minutes after administering drug and frequently thereafter for next 12 hr

• Premedication and medication withdrawal

  • Carbidopa blocks systemic/peripheral decarboxylation of fluorodeoxyphenylalanine 18F-DOPA injection to increase uptake in the brain; administer carbidopa 150 mg PO at least 60 minutes (and no longer than 120 minutes) before administration
  • Instruct the patient to discontinue medications for Parkinson disease 12 hr before administering fluorodeoxyphenylalanine 18F-DOPA

• Imaging guidelines

  • Instruct patient to void immediately before imaging and 70 minutes post administration
  • Start imaging at ~80 minutes post administration (with a 9-second CT scan for attenuation correction) followed by 3-dimentional PET scan from 80-100 minutes post administration

IV Administration

Infuse IV over 1 minute before PET imaging

Minimize dose consistent with the objectives of the procedure and the nature of the imaging cameras used

Storage

Store vial upright in lead-shielded container at 25ºC (77ºF); excursions permitted to 15-30ºC (59-86ºF)

Avoid direct light

Use within 10 hr from the time of the end of synthesis (EOS)