Additional levodopa for muscle and joint pain

Intervention: This is a randomized, double-blind, placebo-controlled clinical trial. Participants will be randomized to receive either additional dopaminergic replacement therapy (DRT group) or placebo tablets (placebo group). Randomization will be performed using a computer-generated sequence, and both participants and outcome assessors will remain blinded to treatment allocation. A total of 90 patients will be included, with 60 patients allocated to the DRT group and 30 patients allocated to the placebo group. Within the DRT group, 30 patients will receive a 10% increase in their daily levodopa equivalent dose (LED) using levodopa/benserazide (Prolopa®) tablets, and 30 patients will receive a 20% increase in their daily LED with the same formulation. Within the placebo group, 15 patients will receive placebo tablets in a number equivalent to a 10% increase in LED, and 15 patients will receive placebo tablets in a number equivalent to a 20% increase in LED. Levodopa/benserazide (Prolopa®) will be used as the active drug in the intervention group, with dosages individually adjusted to provide either a 10% or 20% increase in baseline daily LED while maintaining the existing therapeutic regimen. Placebo tablets will be identical in appearance, size, and color to the active tablets. All placebo tablets will be manufactured to be indistinguishable from the active levodopa/benserazide tablets, with packaging, labeling, and dispensing following good clinical practice standards to ensure complete blinding of participants, investigators, and outcome assessors. The intervention period will last for 2 weeks, after which participants will undergo reassessment according to the study protocol, and the assigned treatment will be discontinued. Primary outcome: Proportion of individuals presenting with 50% or more reduction in the average pain intensity, assessed by the verbal numeric pain rating scale (Brief Pain Inventory item 5) at the end of two-week follow-up period, when compared to baseline values. Secondary outcome: The total score of the Parkinson's Disease Pain Classification System (PD-PCS) at the end of the 2-week follow-up period.;The scores of the Brief Pain Inventory at the end of the two-week follow-up period.;The score of the PDQ-8 (8-item Parkinson's Disease Questionnaire) at the end of the 2-week follow-up period.;The total score of The Hospital Anxiety and Depression Scale (HADS), as well as of its anxiety and depression subscales, at the end of the 2-week follow-up period.;The score of the Clinical Global Impression of Change scale at the end of the 2-week follow-up period.;The scores of the Patient Global Impression of Change scale at the end of the 2-week follow-up period.;The score of the MDS-UPDRS (Movement Disorders Society - Unified Parkinson's Disease Rating Scale) Part III scale at the end of the end of the 2-week follow-up period.