Progress in understanding the extent and role of gastrointesti- nal dysfunction in Parkinson's disease (PD) has significantly advanced over the past decade. PD is believed to be associ- ated not only with the loss of dopaminergic neurons in the substantia nigra of the midbrain, but also with a range of peripheral metabolic changes, including those in the liver. Autonomic dysfunction is recognized as a key non-motor feature of PD. This study aimed to investigate the effect of a novel benzodiaze pine derivative, metresdiazenone, on the lipid composition of bile in a rotenone-induced rat model of Parkinsonian syndrome (PS). Compared to control animals, rotenone exposure led to a decrease in bile concentrations of phospholipids, cholesterol, cholesterol esters, and triglycerides by 23.6%, 24.5%, 29.3%, and 38.1%, respectively, with no significant change in free fatty acid content. Administration of metresdiazenone at a dose of 1 mg/kg restored bile lipid levels nearly to baseline: phospholipids (100%), cholesterol (82.2%), cholesterol esters (87.5%), and triglycerides (82.1%). At higher doses (2 and 4 mg/kg), bile concentrations of phospholipids exceeded control values by 12.5% and 25.3%, cholesterol by 12.4% and 11.7%, cholesterol esters by 11.3% and 19.5%, triglycerides by 20.7% and 31.2%, and free fatty acids by 10.1% and 14.2%, respectively. These findings indicate that metresdiazenone at 1 mg/kg effectively restores impaired lipid metabolism in the liver in the rotenone model of PS, while higher doses lead to a marked increase in triglyceride levels.