Evaluation of the Efficacy and Safety of Fecal Microbiota Transplantation for Constipation in Parkinson's Disease

Participants will be allocated to FMT group or placebo group at a 1:1 ratio. For interventional group, patients will be given six FMT capsules twice a week for 24 weeks. Placebo capsules are identical in appearance and smell but contain milk powder. At each follow-up visits, participants complete specific scales to assess improvement in constipation, emotion and quality of life. Besides, fecal samples are collected for metagenomics and metabolomics sequencing and blood samples are tested peripheral concentration of levodopa.