Sustained striatal dopamine levels following intestinal levodopa infusions in Parkinson's disease patients

Background The objective of this study was to investigate in vivo the ability of levodopa/carbidopa intestinal gel infusions to produce sustained striatal dopamine levels and to improve clinical outcomes in Parkinson's disease patients. Methods Six advanced Parkinson's disease patients had serial [11C]raclopride PET to assess levodopa/carbidopa intestinal gel infusion‐induced rises in striatal dopamine as reflected by a fall in dopamine‐D2/3 receptor availability. Parkinson's disease patients had baseline scan OFF‐dopaminergic stimulation and 2 scans following initiation of levodopa/carbidopa intestinal gel infusions. Striatal D2/3 binding was measured in striatal subregions corresponding to sensorimotor, limbic, and cognitive/associative function. Results Mean striatal [11C]raclopride nondisplaceable binding potential decreased by 14.0% to 16.7% in sensorimotor, 12.0%‐14.4% in limbic, and 8.7%‐11.6% in cognitive/associative function subregions at 1‐ to 10‐hour points (P < 0.01). Sensorimotor subregion [11C]raclopride nondisplaceable binding potential reductions correlated with reductions in Unified Parkinson's Disease Rating Scale Part III scores over the course of the infusion (r = 0.81; P < 0.05). Conclusions Levodopa/carbidopa intestinal gel infusions generate a stable rise in striatal dopamine levels and are associated with improvements in motor manifestations.