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Section 1 Introduction. The physicochemical properties of drugs that predispose (????) them to good absorption, such as lipophilicity (???) , are impediment(??) to their elimination. As a consequence, the elimination of drugs normally requires their conversion into water soluble compounds by a pr
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1. Chapter 3 Chemical Structure and Metabolism ??? ?????????
2. Section 1 Introduction The physicochemical properties of drugs that predispose (????) them to good absorption, such as lipophilicity (???) , are impediment(??) to their elimination.
As a consequence, the elimination of drugs normally requires their conversion into water soluble compounds by a process of metabolism, which enables excretion via urine or faeces(???).
3. Metabolism Metabolism is often the major factor defining the pharmacokinetics of drugs, which in turn can influence the efficacy and side-effect profile of these compounds.
The chemical nature and means of identification of these biotransformations have been well known for many years, but in recent years major advances have been made in the understanding of the enzymes responsible for the metabolic pathways.
4. Section 2 Enzymes for Drug Metabolism (??? ??????) The drug metabolizing enzymes are usually classified by the reactions they catalyse, as either Phase I or Phase II.
5. Phase I Biotransformation Phase I reactions introduce, or otherwise produce, a functional group (e.g. OH, -SH, -NH2, -COOH) into the molecule. These reaction include hydrolysis (??) , reduction (??) and oxidation (??) and are performed by a wide range of enzymes. Often these Phase I reactions precede Phase II biotransformations. ?I?????????????,?????????????????,???????????????,?????????????