Efficacy of oral administration of licorice as an adjunct therapy on improving the symptoms of patients with Parkinson's disease, A randomized double blinded clinical trial

Licorice preparations are used as neuroprotective remedies in Persian ethnomedicine, in order to prevent from disabilities in neurodegenerative conditions like Parkinson's disease (PD). This study was designed to determine the licorice (root of Glycyrrhiza glabra L.) effectiveness as an adjunct treatment in the PD management. In this double-blinded trial, 128 patients were assessed for eligibility criteria. Seventy-eight patients were ineligible and 11 of them refused from participating. Thirty-nine PD patients (YAHR staging ≤ 3) were divided into two groups by random. The patients received oral licorice or placebo syrups with a dose of 5 cc, twice a day for 6 months. High-performance liquid chromatography and spectrophotometric instruments determined licorice syrup constituents. The patients' situation for Unified Parkinson's rating scale (UPDRS) was assessed every 6 weeks for the duration of six months. In addition, patients' blood pressure, blood glucose, sodium and potassium levels, quality of life and dizziness were determined. Six weeks after intervention, total UPDRS, daily activities and tremor were significantly improved with a considerable effect size. A significant better motor test and rigidity scores were observed 4 months after licorice intake (p > 0.05). No electrolyte abnormality, significant changes in blood pressure or blood glucose levels were observed during the study. Each 5cc of syrup contained 136 mg of licorice extract with 12.14 mg glycyrrhizic acid, and also 136 μg of polyphenols. The licorice intake could improve the symptoms in PD patients without serious adverse events. [Display omitted]