phases of drug metabolism
Drug metabolism typically occurs in two main phases: Phase I and Phase II. These processes play a crucial role in transforming drugs into more water-soluble compounds that can be easily excreted from the body. 1. Phase I Metabolism: - Enzymes Involved: Cytochrome P450 (CYP) enzymes are central to Phase I metabolism. - Reactions: Oxidation, reduction, and hydrolysis reactions take place during this phase. These reactions aim to introduce or expose functional groups on the drug molecule, making it more amenable to subsequent conjugation reactions in Phase II. - Products: The metabolites produced in Phase I reactions are often more polar than the original drug but are not necessarily sufficiently water-soluble for excretion. 2. Phase II Metabolism: - Enzymes Involved: Various enzymes, including transferases, glucuronosyltransferases, sulfotransferases, and others, facilitate Phase II reactions. - Reactions: Conjugation reactions occur, where the drug or its Phas