Novel contribution to the simultaneous monitoring of pramipexole dihydrochloride monohydrate and levodopa as co-administered drugs in human plasma utilizing UPLC-MS/MS

Application of net analyte signal and principal component regression for rapid simultaneous determination of Levodopa and carbidopa in commercial pharmaceutical formulation and breast (human) milk sample using spectrophotometric method

In this study, a UV-vis spectrophotometric method coupled with net analyte signal (NAS) and principal component regression (PCR) as multivariate calibration methods were used for the simultaneous determination of levodopa (LEV) and carbidopa (CBD) in prepared mixtures, pharmaceutical formulation, and breast milk sample. The mean recovery of the NAS model was 98.10% and 99.60% for LEV and CBD, respectively. Also, the relative standard deviation (RSD%) values were found to be lower than 5.5% and 4% for LEV and CBD, respectively. On the other hand, the mean recovery of LEV and CBD related to the PCR method was obtained at 96.86% and 92.43%, respectively. K-Fold cross-validation was used to estimate the number of components, which was 7 and 3 with a mean square error prediction (MSEP) of 1.50 and 7.14 for LEV and CBD, respectively. The results revealed that the NAS model was better than the PCR model. Additionally, the proposed NAS-based calibration method was successfully developed for the simultaneous analyses of LEV and CBD in a commercial tablet and breast milk.

Determination of levodopa by chromatography-based methods in biological samples: a review

Levodopa (L-DOPA) is the most effective drug for Parkinson's disease; however, various side effects occur during therapy. L-DOPA metabolites and the high cumulative dose of L-DOPA were responsible for its side effects. It is necessary to monitor the concentration of L-DOPA and its metabolites for individualized therapy. This review focuses on L-DOPA analysis by chromatography-based methods in biological matrices. Literature published up to September 2021 was collected in the PubMed, Web of Science, and Embase by using search strategy ("levodopa" OR "L-DOPA") AND ("chromatography"). A total of 1249 articles were identified and 32 articles were included. The contents for method development and validation were summarized and analyzed. Due to the instability of catecholamines (L-DOPA, dopamine, and 3-O-methyldopa) and carbidopa, antioxidation (0.5 mg sodium metabisulfite for 100 μL sample) and environment temperature control were used alone or in combination to enhance stability. Sample was mainly pretreated by protein precipitation (0.4-0.7 M perchloric acid). Separation was usually achieved using methanol or acetonitrile:water (with formic acid) on C18 columns. Mass spectrometry, electrochemical detector, ultraviolet-visible detector and fluorescence detector were used for detection. For L-DOPA, the calibration range was 2.5-10,000 ng/mL, the matrix effect and its coefficient of variation was 85-115 and -9.0-8.5%, and the recovery was 66.8-127.0%. Without stabilization strategy, L-DOPA was stable in plasma at room temperature for 1-7 h (4-6 h for most studies), at - 70 °C to - 80 °C for 10-20 days and after 3-5 freeze-thaw cycles. With stabilization strategies, the stability of L-DOPA in plasma was significantly improved. Metabolites of L-DOPA and enzyme inhibitors (carbidopa, entacapone, tolcapone and benserazide) were all stable in biological matrix. This study might be useful for researchers to develop their methods for individualized therapy of patients with Parkinson.