| 摘要: | 本研究的目的以家兔為實驗動物，同時以肌肉注射方式給與L-dopa/carbidopa及caffeic acid，以研究它們之間是否會產生交互作用。
首先，將L-dopa以肌肉注射方式投予家兔，探討L-dopa劑量依存性之藥物動力學。先以三種不同劑量的L-dopa/carbidopa (2/0.5, 5/1.25, and 10/2.5 mg?kg-1)經肌肉注射及經靜脈注射一種劑量之L-dopa/carbidopa (2/0.5 mg?kg-1)，依交叉試驗方式分別投予六隻雄性兔子，在投藥後採血，取血漿樣品並以高壓液相層析儀分析L-dopa及3-O-methyldopa (L-dopa 之代謝物, 3-OMD)之濃度，再經由所得之數據決定L-dopa與3-OMD之藥物動力學之模式。由結果得知，L-dopa經肌肉注射後會被快速吸收，並於30分鐘內達到最高濃度，但3-OMD的形成則較慢，須於120-180分鐘後才達到最高點。L-Dopa經肌肉注射後之生體可用率為0.70-1.21，而3-OMD 形成之相對比率為 0.79-1.24；另於不同劑量間，L-dopa之肌肉注射生體可用率及3-OMD形成比率並不具統計上的差異。此外，L-dopa與3-OMD於排除半衰期上也不具統計上的差異；而在曲線下面積(AUC)及血漿中最高濃度值(Cmax)，L-dopa與3-OMD於L-dopa/carbidopa在2/0.5-10/2.5 mg?kg-1劑量範圍內亦呈現正比增加之現象。由此可知，L-dopa與3-OMD在此劑量範圍內無劑量依存性之藥物動力學現象。
此外，對於caffeic acid 與 L-dopa 之交互作用實驗，首先將六隻家兔以交叉投予方式(crossover)，分別以肌肉注射投予單一劑量之L-dopa/carbidopa (5/1.25 mg?kg-1)或caffeic acid (5 mg?kg-1)，接著再同時投予 L-dopa/carbidopa (5/1.25 mg?kg-1) 與三種不同劑量之caffeic acid (分別為 2.5, 5 及10 mg?kg-1)，而後採血分析血中 L-dopa、3-OMD、caffeic acid 及 ferulic acid 之濃度，並計算其相關之藥物動力學參數，結果得到當投予10 mg?kg-1的caffeic acid時，不僅3-OMD的形成會降低22%，而且3-OMD之Cmax會下降31%；此外L-dopa之代謝率(Metabolic ratio, AUC of 3-OMD/AUC of L-dopa) 也會減少22%。此結果顯示，caffeic acid可有意義的減少3-OMD之形成(p < 0.05)，但L-dopa/carbidopa則對caffeic acid 及ferulic acid的藥物動力學參數則沒有影響，因此我們認為L-dopa/carbidopa與10 mg?kg-1的caffeic acid同時投予時會明顯的影響L-dopa經COMT pathway的代謝。
由於當 L-dopa/carbidopa與caffeic acid同時投藥時 L-dopa 的血中濃度雖有增加趨勢，但因變異性太大而未達到統計學上之有意義的差異，因此將 caffeic acid 提高劑量投予，評估能否增加 caffeic acid的影響。之後，再分別投予其他多酚類化合物，包括: dihydrocaffeic acid 與 catechin，評估其是否亦有交互作用的存在。將六隻家兔以交叉投予方式(crossover)，分別以肌肉注射投予單一劑量之L-dopa/carbidopa (5/1.25 mg?kg-1)，而後再同時投予 L-dopa/carbidopa (5/1.25 mg?kg-1) 與高劑量(50 mg?kg-1)之三種不同化合物，caffeic acid、catechin 與dihydrocaffeic acid (DHCA)，而後採血分析血中 L-dopa、3-OMD 與 carbidopa 之濃度，並計算其相關之藥物動力學參數，結果得到當 L-dopa 分別與高劑量的 caffeic acid、dihydrocaffeic acid (DHCA)與 catechin併用後，所得L-dopa 之 AUC0-t、AUC0-?V 與 Cmax 皆比單獨投予 L-dopa/carbidopa 結果高，而除了與 catechin 併用所得之 Cmax 數值外，其餘皆達到統計學上有意義的差異(p < 0.05)。而三種化合物影響 L-dopa 之程度則以 DHCA 最大，其AUC0-t、AUC0-?V 與 Cmax 分別增加 64%、64% 與 68%。每次投藥後，所得3-OMD 之平均AUC0-t、AUC0-?V 與 Cmax之數值皆較單獨投予L-dopa 之數值低，然而，此差異除了與 caffeic acid併用結果外，其餘數值皆達到統計學上有意義的差異 (p < 0.05)。此外，與 catechin 併用下降程度最大，其3-OMD 之AUC0-t、AUC0-?V 與 Cmax 分別減低 65%、64% 與 64%，而且catechin 亦降低 3-OMD平均代謝比率達 76%。
由於 catechin 對L-dopa 經 COMT 途徑代謝的影響程度最大，因此進一步探討投予較低劑量的 catechin時，此影響是否仍然存在。將六隻家兔以交叉投予方式(crossover)，分別以肌肉注射投予單一劑量之L-dopa/carbidopa (5/1.25 mg?kg-1)，而後再同時分別投予L-dopa/carbidopa (5/1.25 mg?kg-1) 及三種劑量的catechin (10 mg?kg-1、20 mg?kg-1與50 mg?kg-1)，經由採血分析血中 L-dopa、3-OMD、carbidopa 與 catechin 之濃度，並計算其相關之藥物動力學參數，結果得到當 L-dopa 分別與三種不同劑量的 catechin 同時投予後，可發現當併用時，所得L-dopa 之 AUC0-t、AUC0-?V 與 Cmax皆比單獨投予 L-dopa/carbidopa 結果高，除了同時給予 50 mg?kg-1 之catechin時所得Cmax 數值以外，其餘皆可達到統計學上有意義的差異(p < 0.05)。而以與 20 mg?kg-1 之catechin 同時投予後，其AUC0-t、AUC0-?V 與 Cmax 分別增加 78%、83% 與 82%，且其增加的程度最大。3-OMD 之AUC0-t、AUC0-?V 與 Cmax所得數值亦皆較單獨投予L-dopa 之數值低，其數值皆達到統計上之有意義的差異。除了併用 10 mg?kg-1 之catechin時所得AUC0-?V 數值以外，其餘數值皆達到統計上之有意義的差異(p < 0.05)，但仍以與50 mg?kg-1 之catechin 同時投予後，其AUC0-t、AUC0-?V 與 Cmax 的分別下降程度最大。而三種劑量下降3-OMD平均代謝比率的幅度分別為56%、68% 與 76%，其影響程度與catechin劑量有關。
綜合以上實驗結果可知，若巴金氏症病患在服用 L-dopa 時，也併服含有多酚類 (polyphenols, 包括: caffeic acid、DHCA 或 catechin) 之飲料或水果 (如: 綠茶飲料、咖啡或奇異果等)，有可能由於多酚類化合物抑制 COMT 的作用，因此增加 L-dopa 之可用率及降低 3-OMD 之生成，相對也增加 L-dopa 之治療效果。
The purpose of this study was to investigate the drug interaction between caffeic acid and L-dopa. Both caffeic acid and L-dopa/carbidopa were simultaneously administered to rabbits via an intramuscular (IM) injection.
First, the dose-dependent pharmacokinetics of levodopa (L-dopa) was studied in rabbits via an intramuscular administration. Three different doses of L-dopa/carbidopa (2/0.5, 5/1.25, and 10/2.5 mg?kg-1) were administered to six male rabbits via an IM route, and one dose of L-dopa/carbidopa (2/0.5 mg?kg-1) was administered via an intravenous (IV) route with a washout period of 1-week between different doses in a crossover treatment protocol. Plasma samples were collected after each treatment and the concentrations of L-dopa and 3-O-methyldopa (an L-dopa metabolite, 3-OMD) were measured by a sensitive high-performance liquid chromatographic (HPLC) method. Subsequently, these measurements were used to determine the pharmacokinetic behavior of L-dopa and 3-OMD. The results indicated that the absorption of L-dopa was fast with the time to the peak within 30 min, but the formation of 3-OMD was slow with the time to the peak of 120-180 min after IM administration. The IM bioavailability of L-dopa was in the range of 0.70-1.21, and the relative ratios of the formation of 3-OMD at different doses of L-dopa were in the range of 0.79-1.24. No statistically significant difference could be observed for IM bioavailability of L-dopa or for the relative ratios of the formation of 3-OMD in this dose range. The elimination half-lives of L-dopa and 3-OMD also exhibited no significant differences for each dose after IM administration. In addition, both the area under the curve (AUC) and maximum plasma concentration (Cmax) values of L-dopa and 3-OMD increased proportionally over the dose range of 2/0.5–10/2.5 mg?kg-1 for L-dopa/carbidopa, suggesting that L-dopa and 3-OMD obeyed dose-independent pharmacokinetics.
The impacts of caffeic acid on the pharmacokinetics of L-dopa were studied in rabbits. A single dose of 5/1.25 mg?kg-1 L-dopa/carbidopa was administered alone or was co-administered with three different doses of caffeic acid (2.5, 5, and 10 mg?kg-1), or a single dose of 5 mg?kg-1 caffeic acid was administered alone via an IM route to six rabbits each in a crossover treatment protocol. Plasma levels of L-dopa, 3-O-methyldopa (3-OMD), caffeic acid, and ferulic acid were determined and subsequently used to calculate their pharmacokinetic parameters. The results indicated that caffeic acid administered at a dose of 10 mg?kg-1 decreased about 22% of the peripheral formation of 3-OMD and about 31% of the Cmax of 3-OMD. In addition, the metabolic ratios (MR, AUC of 3-OMD/AUC of L-dopa) decreased by about 22%. Results also indicated that caffeic acid significantly decreased the proportion of 3-OMD (p < 0.05). In contrast, the parameters of neither caffeic acid nor ferulic acid were significantly affected by L-dopa/carbidopa. In conclusion, caffeic acid at a dose of 10 mg?kg-1 can significantly affect the COMT metabolic pathway of L-dopa.
When L-dopa/carbidopa and caffeic acid were simultaneously administered, plasma level of L-dopa was increased. Due to large variance, the value did not show statistically significant differences. Therefore, to evaluate the effect of caffeic acid in higher dose with L-dopa, the investigation was carried out. In addition, L-dopa/carbidopa was simultaneously administered with other polyphenols including dihydrocaffeic acid and catechin to evaluate the drug interactions between L-dopa and dihydrocaffeic acid or catechin. A single dose of 5/1.25 mg?kg-1 L-dopa/carbidopa was administered alone or L-dopa/carbidopa was co-administered with high dose (50 mg?kg-1) of three different compounds including caffeic acid, dihydrocaffeic acid (DHCA) and catechin via an IM route to six rabbits each in a crossover treatment protocol. Plasma levels of L-dopa, 3-O-methyldopa (3-OMD), and carbidopa were determined and subsequently used to calculate their pharmacokinetic parameters. The results indicated that AUC0-t, AUC0-?V and Cmax values of L-dopa were more than the values of L-dopa after administered L-dopa alone. These data were all show statistically significant differences (p < 0.05) except the Cmax values of L-dopa for co-administered with catechin. DHCA affected L-dopa availability the most among these compounds. The AUC0-t, AUC0-?V and Cmax values of L-dopa were all increased 64%, 64% and 68%, respectively. After all treatments, AUC0-t, AUC0-?V and Cmax values of 3-OMD were less than the values of 3-OMD after administered L-dopa alone. These difference were all show statistically significant differences (p < 0.05) except the AUC0-t, AUC0-?V and Cmax values of 3-OMD for co-administered with caffeic acid. Catechin affected 3-OMD data the most among these compounds. The AUC0-t , AUC0-?V and Cmax values of 3-OMD were all decreased 65%, 64% and 64%, respectively. Besides, catechin reduced metabolic ratio of 3-OMD to 76%.
Because catechin affects L-dopa metabolism by COMT pathway the most among these compounds, it intrigues us to advance investigation whether still exists drug interaction between the lower dose of catechin and L-dopa. A single dose of 5/1.25 mg?kg-1 L-dopa/carbidopa was administered alone or L-dopa/carbidopa was co-administered with three different doses of catechin (10, 20, and 50 mg?kg-1) via an IM route to six rabbits each in a crossover treatment protocol. Plasma levels of L-dopa, 3-OMD, carbidopa and catechin were determined and subsequently used to calculate their pharmacokinetic parameters. The results indicated that L-dopa was co-administered with three different doses, AUC0-t , AUC0-?V and Cmax values of L-dopa were more than the values of L-dopa after administered L-dopa alone. These data were show statistically significant differences (p < 0.05) except the Cmax values of L-dopa for co-administered with catechin (50 mg?kg-1). Catechin (20 mg?kg-1) affected L-dopa availability the most among these compounds. The AUC0-t , AUC0-?V and Cmax values of L-dopa were increased 78%, 83% and 82%, respectively. After all treatments, AUC0-t, AUC0-?V and Cmax values of 3-OMD were less than the values of 3-OMD after administered L-dopa alone. These differences all were show statistically significant differences (p < 0.05). 50 mg?kg-1 of catechin affected 3-OMD data the most among these doses. After co-administered with 10, 20 and 50 mg?kg-1 of catechin, the metabolic ratio mean of 3-OMD was decreased 56%, 68% and 76%, respectively. The effects were dependent on catechin doses.
From the above studies, we inferred that PD patients simultaneously received L-dopa and beverage or fruits containing polyphenols, the polyphenols would inhibit L-dopa metabolism by COMT pathway. Therefore, polyphenols would enhance L-dopa bioavailability and reduce 3-OMD formation, and then increased L-dopa response for PD treatment. |
