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False-positive 123I-FP-CIT scintigraphy and suggested dopamine transporter upregulation due to chronic modafinil

Per Borghammer1, Karoline Knudsen, Erik Danielsen

  • 1From the *Department of Nuclear Medicine and PET Centre, and †Department of Neurology, Aarhus University Hospital, Aarhus, Denmark.

Clinical Nuclear Medicine
|July 24, 2013
PubMed

Insights

Modafinil can cause false positives on dopamine transporter scans (DaTSCAN). Withholding the drug normalized uptake, suggesting modafinil upregulates dopamine transporters.

Area of Science:

  • Neuroimaging
  • Pharmacology
  • Dopamine Transporter Imaging

Background:

  • Ioflupane I-123 injection (I-FP-CIT) SPECT, commonly known as DaTSCAN, is used to assess dopamine transporter (DAT) levels.
  • Decreased striatal uptake on DaTSCAN is indicative of nigrostriatal degeneration, often seen in Parkinsonian syndromes.
  • Medication effects on DaTSCAN results can lead to misinterpretation.

Observation:

  • A 76-year-old male with a movement disorder initially showed universally decreased striatal uptake on DaTSCAN.
  • This result was deemed a false positive after it was discovered the patient was taking modafinil.
  • A follow-up DaTSCAN 43 months later, after withholding modafinil for 7 days, revealed nearly doubled striatal uptake values, exceeding the normal upper limit.

Findings:

  • Chronic modafinil treatment appears to pharmacologically upregulate dopamine transport capacity.
  • Modafinil can induce a reversible increase in striatal dopamine transporter density or function.
  • The observed increase in striatal uptake suggests a significant drug-induced effect on DAT levels.

Implications:

  • DaTSCAN results in patients taking modafinil should be interpreted with caution.
  • Understanding medication interferences is crucial for accurate diagnosis in neurodegenerative movement disorders.
  • Further research is warranted to elucidate the precise mechanisms of modafinil's effect on dopamine transporters.

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