IN VIVO METABOLIC ACTIVATION OF CLOPIDOGREL IS INTESTINAL OR HEPATIC CYTOCHROME

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。这项研究的目的是确定我们是否可以证明氯吡格雷（以Plavix的商标出售）在哪里主要被激活。氯吡格雷是治疗和预防心脏病发作的重要药物。当患有冠状动脉疾病的患者服用这种药物时，它会阻止血小板的活动，防止冠状动脉完全堵塞和心脏病发作。在最近的一项研究中，我们发现并非所有患者对氯吡格雷的反应都一样。换句话说，氯吡格雷对一些病人比其他病人更有效。在我们的研究中，对氯吡格雷的反应是通过血液测试来确定的，该测试测量了血小板聚集的百分比。包括氯吡格雷在内的许多药物都需要一种酶（细胞色素P450 3A4），这种酶存在于肝脏和小肠内壁细胞中，以激活代谢，使药物有效发挥作用。目前尚不清楚氯吡格雷是否在肠内膜细胞或肝脏中被代谢激活。本研究旨在确定氯吡格雷的代谢激活主要是通过肠道CYP3A4还是通过肝脏（肝系统）中的CYP3A4。我们将使用红霉素这是一种已知的肝脏CYP3A4抑制剂和葡萄柚汁这是一种已知的肠道CYP3A4抑制剂。当这些药物与氯吡格雷联合服用时，我们可以通过测量CYP3A4活性的测试来确定氯吡格雷的激活途径。在给予氯吡格雷和葡萄柚汁后，咪达唑仑的血液水平将被用来测量主要在小肠中对CYP3A4活性的抑制。红霉素呼气试验将主要用于测量红霉素给药后肝脏对CYP3A4活性的抑制作用。咪达唑仑试验和红霉素呼吸试验对我们确定氯吡格雷在何处代谢是必要的。这项研究招募了对氯吡格雷反应正常的成年人。参与者将被随机分配接受氯吡格雷和红霉素或氯吡格雷和西柚汁。如果与氯吡格雷联合服用时，肝脏CYP3A4活性被红霉素（通过呼吸试验测量）抑制，则预计氯吡格雷的代谢激活将被抑制（对血小板的反应将减弱），这将表明氯吡格雷在肝脏中被激活。另一方面，我们知道西柚汁是小肠中CYP3A4的抑制剂。如果肠道CYP3A4活性被葡萄柚汁抑制（通过咪达唑仑试验确定），则氯吡格雷的代谢激活将被抑制，这表明氯吡格雷在肠细胞壁中被激活。本研究将招募30名对氯吡格雷反应正常的受试者。每个受试者将被随机分配到氯吡格雷和红霉素组或氯吡格雷和西柚汁组。将在方案中列出的特定时间点进行血液采样，以测量血小板功能和咪达唑仑水平。f给予葡萄柚汁后，CYP3A4主要在小肠内的活性。红霉素呼气试验将测量的抑制CYP3A4活性主要在肝脏后给予罗罗霉素。这两项测试对于我们确定氯吡格雷在何处代谢是必要的。氯吡格雷的抑制作用意味着，当服用氯吡格雷时，血小板对氯吡格雷的反应不如不服用葡萄柚汁或trolleandomycin时有效。如果与氯吡格雷合用时，肝脏CYP3A4活性被troleandomycin（通过呼气试验测量）抑制，则预计氯吡格雷的代谢激活将被抑制（对血小板的反应将减弱），这将表明氯吡格雷在肝脏中被激活。另一方面，我们知道西柚汁是小肠中CYP3A4的抑制剂。如果肠道CYP3A4活性被葡萄柚汁抑制（通过咪达唑仑试验确定），则氯吡格雷的代谢激活将被抑制，这表明氯吡格雷在肠细胞壁中被激活。这项研究将招募30名年龄在18-60岁的男性和女性，他们来自任何民族或种族，对氯吡格雷反应正常。他们将被随机分配到氯吡格雷和troleandomycin组或氯吡格雷和葡萄柚汁组。在每组的不同时间点进行血液检查，以确定氯吡格雷的激活部位。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This study is designed to determine if we can demonstrate where the medication clopidogrel (sold under the trade name of Plavix) is primarily activated. Clopidogrel is an important drug for the treatment and prevention of heart attacks. When patients with coronary artery disease take this drug, it stops the action of the platelets and prevents total coronary blockage and heart attacks. In a recent study we found that not all patients respond to clopidogrel the same way. In other words, in some patients clopidogrel was more effective than in others. In our studies, the response to clopidogrel is determined by a blood test that measures percent platelet clumping. Many drugs including clopidogrel require an enzyme (cytochrome P450 3A4), which is found in both the liver and the cells lining the small intestine, in order to be metabolically activated so the drugs can work effectively. It is not known whether clopidogrel is metabolically activated in the intestinal lining cells or in the liver. This study has been designed to determine whether the metabolic activation of clopidogrel is primarily by the intestinal CYP3A4 or by the CYP3A4 in the liver (hepatic system). We will use Erythromycin which is a known inhibitor of hepatic CYP3A4 and grapefruit juice which is a known inhibitor of intestinal CYP3A4. When these are taken in combination with clopidogrel, we can determine the route of activation of clopidogrel by doing tests that measure the activity of CYP3A4. Blood levels of midazolam will be used to measure the inhibition of CYP3A4 activity primarily in the small intestine after clopidogrel and grapefruit juice is given. The erythromycin breath test will be used to measure the inhibition of CYP3A4 activity primarily in the liver after Erythromycin is given. Both the midazolam test and the erythromycin breath test are necessary for us to determine where clopidogrel is metabolized. This study recruits adults who respond normally to clopidogrel. Participants will be randomly assigned to receive either clopidogrel and Erythromycin or clopidogrel and grapefruit juice. If the hepatic CYP3A4 activity is inhibited by Erythromycin (as measured by the breath test) when taken in combination with clopidogrel, it is expected that metabolic activation of clopidogrel will be inhibited (response on platelets will be diminished) and would indicate that clopidogrel is activated in the liver. On the other hand, we know that grapefruit juice is an inhibitor of CYP3A4 in the small intestine. If the intestinal CYP3A4 activity is inhibited by grapefruit juice (which is determined by the midazolam test) it is expected that metabolic activation of clopidogrel will be inhibited and would indicate that clopidogrel is activated in the intestinal cell lining. This study will recruit 30 subjects who respond normally to clopidogrel. Each subject will be randomly assigned equally to either the clopidogrel and Erythromycin or clopidogrel and grapefruit juice. Blood sampling will be performed at specific timepoints outlined in the protocol to measure platelet function and to measure levels of midazolam.f CYP3A4 activity primarily in the small intestine after grapefruit juice is given. . The erythromycin breath test will measure the inhibition of CYP3A4 activity primarily in the liver after troleandomycin is given. Both of these tests are necessary for us to determine where clopidogrel is metabolized. Clopidogrel inhibition means that when taken, the response of the platelets to clopidogrel is not as effective as it would be without the grapefruit juice or troleandomycin. If the hepatic CYP3A4 activity is inhibited by troleandomycin (measured by the breath test) when taken in combination with clopidogrel, it is expected that metabolic activation of clopidogrel will be inhibited (response on platelets will be diminished) and would indicate that clopidogrel is activated in the liver. On the other hand, we know that grapefruit juice is an inhibitor of CYP3A4 in the small intestine. If the intestinal CYP3A4 activity is inhibited by grapefruit juice (which is determined by the midazolam test) it is expected that metabolic activation of clopidogrel will be inhibited and would indicate that clopidogrel is activated in the intestinal cell lining. This study will recruit 30 males and females aged 18-60 of any ethnic origin or race who respond normally to clopidogrel. They will be randomly assigned equally to either the clopidogrel and troleandomycin group or clopidogrel and grapefruit juice group. Blood tests will be performed in various time points in each group to determine the site of activation of clopidogrel.