Simultaneous Determination Of Levodopa And 3-O-Methyldopa In Patients With Parkinson'S Disease By High-Performance Liquid Chromatography With Electrochemical Detection

Levodopa remains the main drug in the treatment of patients with Parkinson's disease. Unfortunately, after several years of levodopa treatment, the response duration to each dose shortens as the disease progresses. The present publication describes a rapid, sensitive and precise high-performance liquid chromatographic method (HPLC) with electrochemical detection for the simultaneous analysis of levodopa and its metabolite 3-O-methyldopa (3-OMD) in plasma in patients with Parkinson's disease. The HPLC system used in this study consisted of an isocratic pump, electrochemical detector with the conditioning cell and dual-electrode analytical cell operating in redox mode. The separation was achieved with a ThermoHypersil Gold C-18 reversed phase column, using 0.1 M potassium phosphate, 0.5 mM EDTA, 20 mg/L 1-octanesulfonic acid sodium salt and 1% acetonitrile as a mobile phase (pH = 3.0). The method was optimized and fully validated by determining precision and accuracy, LOD, LOQ, recovery and stability. This method was successfully used in pharmacokinetic studies in 14 patients with Parkinson's disease after oral administration 100 mg levodopa and 25 mg benserazide or 100 mg levodopa and 25 mg carbidopa. Our method is suitable for levodopa therapy monitoring and for investigating the pharmackonietics of the drug in patients with Parkinson's disease.