The Effect of SSRIs on the Binding of (18)F-FP-CIT in Parkinson Patients: A Retrospective Case Control Study

(18)F-FP-CIT [(18)F-fluorinated N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) nortropane] is useful for detecting striatal dopamine transporter (DAT). Since FP-CIT shows relatively high affinities for DAT and serotonin transporter (SERT), its binding can be influenced by selective serotonin reuptake inhibitors (SSRIs). We aimed to evaluate the effect of SSRIs on the binding of (18)F-FP-CIT.

In our (18)F-FP-CIT positron emission tomography (PET) data pool, images of 24 drug-naive Parkinson's disease (PD) patients (62.6 ± 10.6 years), 111 PD patients taking SSRIs [escitalopram (n = 19) and fluvoxamine (n = 20)] or clonazepam (n = 72), and 10 normal people were reviewed. PET images acquired 3 h after (18)F-FP-CIT injection were analyzed by an automated method using a predefined volume of interest (VOI) set of the striatum (ST), occipital cortex (OC), raphe nuclei (RN), and cerebellar cortex (CB). The uptake ratios (URs) of each VOI to the CB were compared among the groups.

The ST/CB URs of all PD groups were significantly lower than that of normal group. When adjusted for drug severity, ST/CB URs were higher in drug-naive group but had no difference among antidepressant groups. Whereas OC/CB URs were not different among groups (p > 0.05), RN/CB URs were significantly lower in SSRI groups than in non-SSRI groups (p < 0.001) and showed similar results when adjusted for disease severity.

PD patients taking SSRIs showed significantly decreased URs in the RN but not the OC. When adjusted for Hoehn and Yar (HY) score, ST URs were not different among antidepressant groups. This result suggests that the OC may be used as a reference region for the quantification of DAT binding in (18)F-FP-CIT PET images of PD patients taking SSRIs.