Background
Patients with Parkinson’s disease (PD) undergoing long-term levodopa therapy are prone to develop levodopa-induced dyskinesia (LID). Amantadine is the main drug recommended for the treatment of LID by current guidelines, but it is far from meeting clinical needs. Tianqi Pingchan Granule (TPG), a compound Chinese herbal medicine, has been developed to relieve symptom of LID.
Objective
This randomized controlled trial evaluated the efficacy and safety of the combination of TPG and amantadine for LID.
Design, setting, participants and interventions
This is a randomized double-blind placebo-controlled trial, conducted from January 2020 to August 2021 at 6 sites in Jiangsu, Zhejiang and Shanghai, China. One hundred PD patients with ≥ 0.5 h of LID were randomly assigned to either the TPG plus amantadine group (TPG group) or the placebo plus amantadine group (placebo group), and treated for a period of 12 weeks. To ensure unbiased results, all study participants, investigators and sponsors were unaware of group allocations. Additionally, the data analysts remained blinded until the analysis was finalized.
Main outcome measures
The primary outcome was assessed using the Unified Dyskinesia Rating Scale (UDysRS) (Range 0–104). The key secondary end point was improvement of motor and non-motor symptoms. Safety analyses included all enrolled patients.
Results
One hundred patients were enrolled and randomized into the two treatment groups. The changes in UDysRS at week 12 were –11.02 for the TPG group and –4.19 for the placebo group (treatment difference –6.83 [–10.53 to –3.12]; P = 0.0004). Adverse events were reported for 2 of 50 patients (4.0%) in each of the groups.
Conclusion
This study indicated that a 12-week treatment of amantadine plus TPG effectively reduced UDysRS scores and was well tolerated, demonstrating the efficacy and safety of TPG for the treatment of LID in PD.
Trial registration: 
ClinicalTrials.gov
 identifier: NCT04173832.

Key words: Parkinson’s disease, Tianqi Pingchan Granule, Levodopa-induced dyskinesia