阿魏酸在家兔體內的藥物動力學與藥效學模式
中文摘要
阿魏酸是一個富含於植物中，屬 hydroxycinnamate 類結構的抗氧化物，可在多種的蔬菜、水果、穀類、稻米中發現。阿魏酸除抗氧化效力
外，尚有抗發炎、抗過敏抗凝血等相關活性 ，然而對於阿魏酸的藥物動力學與藥效學的關聯性仍無完整資料可供參考，本實驗的目的即在 於探討阿魏酸在家兔體內的藥物動力學性質及與其藥效學模式的關聯性。
血液檢品中阿魏酸的測定係採用 HPLC 分析方式，選用逆相層析管柱，配合紫外光偵測，波長設定在 320 nm 。檢量線濃度為每毫升 0.01 到
50 微克間，線性十分良好，且回內分析與回間分析其變異係數皆小於 10% ，回收率也達 95.65% ，顯示此分析方法是良好的阿魏酸血漿檢 品檢測方法。在安定性試驗方面，在室溫 (250C) 下，阿魏酸在 pH 2.62 到 pH 5.10 的緩衝液中下有很好的安定性，但在 pH 鹼性增加緩衝溶 液下有顯著降解發生，檢品酸化保存對定量準確性有助益。
藥物動力學實驗方面選取六隻雄性紐西蘭種白兔，分別給予阿魏酸靜脈注射劑量 5 、 10 、 25 或 75 mg/kg ，及口服投與 50 mg/kg 。在靜脈 注射劑量 5-25 mg/kg 呈二室的藥物動力學性質，其排除半衰期與、清除率數值為線性的藥物動力學性質。在靜脈注射 75 mg/kg 劑量下，血 中濃度與時間關係圖亦呈現為二室性的藥物動力學，但排除半衰期、清除率與 5-25 mg/kg 時大不相同，已呈非線性的藥物動力學。
阿魏酸在家兔口服劑量 50 mg/kg 之後，分析血中濃度變化情形，發現在此劑量下，血中濃度分佈也為二室性的藥物動力學。使用靜脈注射
25 mg/kg 與口服劑量 50 mg/kg 的曲線下面積 (AUCs) ，依劑量調整計算，求其絕對生體可用率為 0.75±0.07 。
本研究亦探討，阿魏酸的抗凝血的藥效學模式，檢測給與阿魏酸後的出血時間 (BT) 、凝血酉每原時間 (PT) 、活化部分凝血激素時間 (aP
TT) 三種時間。在離體試驗中，但是血漿中阿魏酸的濃度大於每毫升 7 微克時， aPTT 測試卻可發現血漿凝結時間有延長現象，以 PT 測試
，血漿凝結時間並未改變，可知阿魏酸對於內在途徑和共同途徑中的凝血因子影響較大。
家兔靜脈注射 25 、 75 mg/kg 和口服投與 50 mg/kg 的阿魏酸後 BT 、 PT 、 aPTT 的凝血時間皆延長，可知阿魏酸在家兔體內有抑制凝血因 子的作用。然而，雖然在離體試驗時含阿魏酸血漿對於 PT 測試的模式較不顯著，但在高劑量下， PT 仍會受影響而延長，可能的原因是高 劑量的阿魏酸下提升血中阿魏酸濃度，促進第Ⅰ、Ⅱ、Ⅴ、Ⅹ對凝血因子的抑制作用，使得在體內實驗時出現明顯 PT 延長作用。
如將血中藥物的濃度變化及藥動參數與凝血時間的改變相比對，兩者之間並無直接的關聯性。如利用平均血中濃度來關聯阿魏酸藥物動力
學與藥效學模式，當平均血中濃度大於每毫升 7 微克時，凝血時間即能延長。因此最明顯的 BT 、 PT 、 aPTT 延長現象，並非發生在阿魏 酸血中濃度最高時，其抗凝血作用最強的時間約在分佈平衡後，排除相開始時。因此阿魏酸產生抗凝血效用，與其藥物平衡有關；但當高 計量時，同時間的血中濃度較高，既使未達分佈平衡狀態，阿魏酸的抗凝血作用即明顯呈現。
Pharmacokinetic and pharmacodynamic model for ferulic acid in rabbits
英文摘要
Ferulic acid is a plant-food-derived antioxidants with hydroxy -cinnamate structure. It is wildly occurring in many kinds of fruits, vegetables, berries a nd grains. Ferulic acid has been studied on their biological potential to protect against various inflammatory related diseases. It also has obvious antico agulant effect. However, it is still lack of about the pharmacokinetic reports of ferulic acid. The aims of this study were to investigate the pharmacokin etics and pharmacodynamic model of ferulic acid in the rabbits.
The plasma concentrations of ferulic acid were determined by an accuracy and simple HPLC method consisted of a reverse phase column with UV det ection at 320 nm. The calibration curve of plasma sample shows good linearity with in the concentration range of 0.01 to 50 mg/ml. The coefficients o f validation (C.V) of the with-run and between-run validation were all within 10%. The recovery of analytical process in plasma was found to be 95.65
%. The stability of ferulic acid in various pH buffer solutions was investigated. The result shows that ferulic acid was very stable in pH 2.62~pH 5.10 a t room temperature (25oC), but at pH 6.66~pH 9.62 it would degrade progressively after six hours.
Ferulic acid was given intravenously with dose of 5,10,25,75 mg/kg and oral 50 mg/kg, to six male New Zealand white rabbits. The pharmacokinetics of ferulic acid after intravenous administration at dose 5-25 mg/kg in rabbits can be described with two-compartment model. There were no significant different in elimination half-life and systemic clearance under these three doses. It results in a linear pharmacokinteics of ferulic acid in rabbits. After t he intravenous administration dose of 75 mg/kg the concentration-time profiles can be fitted to two compartments. But the distribution and elimination phase are changed by the dose-dependent pharmacokinetics.
After the oral administration of the dose 50 mg/kg of ferulic acid to rabbits, the plasma concentration-time profiles could be fitted by a two-compartme nt model. The mean absolute bioavailability of ferulic acid was estimated of 0.75±0.07 by using the value of AUC following the intravenous administr ation dose of 25 mg/kg.
The pharmacodynamic effects of ferulic acid were measured from its anticoagulant response. Three kinds of anticoagulant effects such as BT (bleedin g time), TT (thrombin time), PT (prothrombin time) and APTT (activated partial thromboplastin time) were measured. A series of in vitro experiments proved an anticoagulant of ferulic acid, measured by aPTT and PT. When the ferulic acid concentration in plasma was over the 7μg/ml, the aPTT was prolonged but the PT was normal. The prolongation of aPTT is seen with several deficiencies of the factors in intrinsic and common pathway.
In this the animal experiment, three male New Zealand white rabbits were used. No matter intravenous administration 25, 75 mg/kg and oral administr ation 50mg/kg of ferulic acid were gived to rabbits, the prolongation effects of BT, aPTT and PT can be determination.
In addition, 25 mg/kg of ferulic acid intravenous administration to rabbits, the PT had not prolongation. In 50 mg/kg, 75 mg/kg of ferulic acid was oral and intravenous administration, the PT have prolongation. It may possible have a high plasma concentration due to a high dose of ferulic acid. The fact ors of , , , just can be inhibition, and lead to PT prolongation.Ⅰ Ⅱ Ⅴ Ⅹ
There is no direct relationship existed between the plasma concentration and the clotting time. But we can explain correlation of pharmacokinetic/ phar macodynamic at the steady-state plasma concentration. Steady-state plasma concentration lower than 7μg/ml potency will disappear. Therefor 7μg/ml i s minimum effective drug concentration. Prolonged of BT, aPTT and PT was not observed at peak concentration (Cmax) after oral administration and at distribution phase end after intravenous administration of ferulic acid. So we can suggest that, the anticoagulant effects were occurred when the feru lic acid was distributing through out in the body.
