The effect of levodopa therapy on dopamine transporter SPECT imaging with 123I-FP-CIT in patients with Parkinson's disease

Purpose: The aim of this study was to evaluate, by means of I-123-FP-CIT SPECT, the effect of chronic treatment with levodopa on striatal dopamine transporter (DAT) in patients with Parkinson's disease. Methods: Fifteen patients under stable levodopa/carbidopa monotherapy were imaged twice: at baseline on medication and after at least 20 days of treatment wash-out. DAT levels were assessed from SPECT imaging for the entire striatum, the right and left striatum, the right and left putamen and the right and left caudate, as a ratio of regional brain activities using the formula: (striatal region of interest-occipital)/occipital. Results: During levodopa wash-out, despite a worsening in patients' clinical disability (H&Y mean stage 2.53 +/- 0.58 versus 1.73 +/- 0.45 on therapy, p < 0.001), striatal I-123-FP-CIT levels were not significantly different from those at baseline in any of the brain regions examined. Conclusion: The results of this study suggest that levodopa does not affect I-123-FP-CIT brain imaging and confirm that it is not necessary to withdraw this medication to measure DAT levels with SPECT.