Levodopa 與 Caffeic Acid 之藥物交互作用
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 aci d 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 caffei c 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/c arbidopa (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 catec hin 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 Cm ax 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 AUC 0-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 A UC0-?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。
Drug Interaction of Levodopa with Caffeic Acid
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 mea surements 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 w ithin 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 I M 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 i ncreased 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-ad ministered 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 eac h 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 abo ut 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 signific antly 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 concl usion, 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 sig nificant 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 simultaneo usly administered with other polyphenols including dihydrocaffeic acid and catechin to evaluate the drug interactions between L-dopa and dihydrocaffeic acid or catechin. A sin gle 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 inclu ding 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-O MD), 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 in creased 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 a lone. 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 aci d. 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 b etween 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 d ifferent 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 catechi n were determined and subsequently used to calculate their pharmacokinetic parameters. The results indicated that L-dopa was co-administered with three different doses, AU C0-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 we re 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.
