The effects of use of medications on striatal dopamine transporter binding assessed by [123I]I-FP-CIT SPECT in patients with Parkinson's disease from the PPMI cohort.

PURPOSE: Several centrally acting medications may interfere with dopamine transporter (DAT) imaging using [¹²³I]I-FP-CIT SPECT, potentially leading to misinterpretation. We therefore evaluated the effects of several medications on striatal DAT binding assessed by [123I]I-FP-CIT SPECT in patients with Parkinson's disease (PD). METHODS: Data were obtained from the Parkinson's Progression Markers Initiative (PPMI). PD patients with abnormal [¹²³I]I-FP-CIT SPECT scans, and available medication and clinical data, were included. The effects of bupropion, venlafaxine, methylphenidate, modafinil, and codeine were assessed. Striatal specific binding ratios (SBRs) of the caudate nucleus and putamen were analysed using multivariable linear regression models adjusted for relevant covariates. RESULTS: Data from 752 PD patients were included. Use of the evaluated medications was associated with lower SBRs in the ipsilateral and contralateral caudate nucleus (-13.5% and -13.7%, respectively) and putamen (-6.5% and -8.2%, respectively; all p < 0.01). Medication-specific analyses showed the largest reductions for methylphenidate and modafinil, with relative reductions in caudate nucleus SBRs of up to -33.2% and -25.5%, respectively (both p < 0.01). In contrast, bupropion and venlafaxine were associated with smaller, but still significant, reductions, whereas no significant associations were observed for codeine. CONCLUSION: Use of methylphenidate and modafinil in particular is associated with significantly reduced striatal [¹²³I]I-FP-CIT binding in PD patients. Medication use should be carefully considered when interpreting DAT SPECT scans. Temporary discontinuation may be considered in selected cases when clinically appropriate.