Helicobacter pylori eradication status is associated with lower motor severity despite similar levodopa pharmacokinetics in Parkinson's disease.

BACKGROUND: Helicobacter pylori (H. pylori) infection has been associated with impaired levodopa absorption and worse motor symptoms in Parkinson's disease (PD). However, the relationships among H. pylori infection, eradication history, levodopa pharmacokinetics, and motor severity remain unclear. METHODS: We retrospectively analyzed 40 patients with PD who underwent standardized levodopa/carbidopa pharmacokinetic testing. Participants were classified as HP-positive, never infected, or prior eradication. Plasma levodopa and carbidopa concentrations were measured serially after administration of 100 mg levodopa and 10 mg carbidopa. Pharmacokinetic parameters, including maximum plasma concentration (Cmax), time to Cmax (Tmax), and area under the concentration-time curve (AUC), were compared among groups. Motor severity was assessed using the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III. RESULTS: No significant differences were observed among the three groups in levodopa or carbidopa pharmacokinetic parameters, including levodopa AUC (p = 0.956). In contrast, MDS-UPDRS Part III scores differed significantly among groups (p = 0.038). Post hoc analysis demonstrated lower motor scores in the prior eradication group than in the HP-positive group (adjusted p = 0.032). Multivariable analysis confirmed an independent association between prior eradication status and lower MDS-UPDRS Part III scores (β = -14.57, p = 0.005). No significant correlation was observed between levodopa AUC and motor severity. CONCLUSIONS: H. pylori eradication status was associated with lower motor severity despite similar levodopa and carbidopa pharmacokinetics. These findings suggest that mechanisms beyond acute levodopa absorption may contribute to the relationship between H. pylori and motor symptoms in PD.