Enzymology of xenobiotic metabolism

外来化学物质，如污染物、药物和其他有毒物质，在人体内代谢(即在消除之前经过化学修饰)。这种由肝脏和其他器官中的酶催化的新陈代谢过程，是药物从体内排出的速度的主要决定因素；这反过来又影响药物的有效性和毒性。。药物代谢率在个体之间差异很大，遗传因素是这种差异的重要来源，可以对药物治疗的反应产生重大影响。当用标准剂量治疗时，“不良代谢物”可能面临过量毒性的风险，而“超快速代谢物”则无法获得治疗益处。对于某些药物，新陈代谢可能会产生一种活性物质，因此相反的情况也适用：超快的代谢物有过量服用的风险。

Foreign chemicals, such as pollutants, drugs, and other toxicants, are metabolized (i.e., chemically modified, prior to elimination) in the human body. This process of metabolism, catalyzed by enzymes in the liver and other organs, is the main determinant of the rate at which a drug is eliminated from the body; this, in turn, influences the effectiveness and toxicity of the drug. . Rates of drug metabolism vary widely among individuals, and genetic factors are an important source of this variation, which can have major effects on response to drug therapy. When treated with standard doses, "poor metabolizers" may be at risk of overdose toxicity while "ultrarapid metabolizers" fail to receive therapeutic benefit. With some drugs, metabolism may generate an active agent, and so the opposite scenario applies: ultrarapid metabolizers risk overdose.