Herbal Medicine Combined with Conventional Treatment for Levodopa-Induced Dyskinesia in Parkinson's Disease: A Systematic Review

Objective: Levodopa-induced dyskinesia (LID) is a common motor complication of long-term levodopa therapy in Parkinson's disease (PD), but conventional treatment options remain limited. This systematic review evaluated the efficacy and safety of herbal medicine combined with conventional treatment for LID.Methods: We searched 10 databases on July 30, 2026, for randomized controlled trials (RCTs). Meta-analysis was performed for the total effective rate (TER) and dyskinesia duration using a random-effects model; other outcomes were synthesized narratively because of scale heterogeneity.Results: Six RCTs (504 participants), all conducted in China, met the inclusion criteria. The herbal medicine plus conventional treatment group (treatment group) had a significantly higher TER (RR=1.35, 95% CI, 1.15-1.58; p=0.0003; I2=8%) and significantly shorter dyskinesia duration (MD=-0.96, 95% CI, -1.62 to -0.29; p=0.005) than the conventional treatment-alone group (control group). All six studies reported significant improvements in dyskinesia-specific outcomes (UPDRS IV, AIMS, TCM Symptom Score, UDysRS) in the treatment group. However, outcomes for overall motor function and quality of life varied across studies. Adverse event reporting was limited. The herbal formulas commonly included herbs that exert tonifying and liver-calming effects and target the liver, spleen, and kidney meridians.Conclusions: Herbal medicine combined with conventional treatment may contribute meaningfully to the management of LID in PD. However, given the heterogeneity (control-group compositions, diagnostic criteria, and outcome measures), short treatment durations, and low methodological quality of the included studies, these findings should be considered preliminary and warrant further validation through large-scale, standardized RCTs.