Drug metabolism

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Introduction to drug metabolism, Phase I and Phase II drug metabolisms, biotransformation of drugs in the body.

Drug absorption: The process by which drugs enter the body and are absorbed into the bloodstream.
Drug distribution: The process by which drugs are distributed throughout the body and delivered to the site of action.
Drug elimination: The process by which drugs are eliminated from the body, usually through urine, feces, or breath.
Drug clearance: The mechanism by which the body removes drugs from circulation.
Phase I drug metabolism: The initial phase of drug metabolism, in which drugs are modified by oxidation, reduction, and hydrolysis reactions.
Phase II drug metabolism: The second phase of drug metabolism, in which drugs are conjugated with various substances to form water-soluble compounds.
Cytochrome P450 enzymes: A group of enzymes that play a key role in drug metabolism.
Drug-drug interactions: The effects of one drug on the absorption, distribution, metabolism, or elimination of another drug.
Factors affecting drug metabolism: Factors that can affect the rate and extent of drug metabolism, such as age, sex, diet, genetics, and disease.
Pharmacokinetics: The study of how drugs are absorbed, distributed, metabolized, and eliminated by the body.
Pharmacodynamics: The study of how drugs interact with the body at the molecular, cellular, and organism levels.
Bioavailability: The fraction of an administered drug that reaches the systemic circulation.
Half-life: The time it takes for the plasma concentration of a drug to decrease by 50%.
Toxicology: The study of the adverse effects of drugs and other substances on the body.
Prodrug: A pharmacologically inactive compound that is converted in vivo to an active drug.
Metabolic activation: The process by which drugs or other substances are converted to reactive metabolites that can cause cytotoxicity or mutagenesis.
Metabolic detoxification: The process by which drugs or other substances are converted to less toxic or inactive metabolites.
Drug design for metabolism: The principles of designing drugs to optimize their metabolism, bioavailability, and therapeutic efficacy.
Drug delivery systems: The strategies for delivering drugs to their site of action, including oral, topical, transdermal, injectable, and inhalable formulations.
Clinical pharmacology: The application of pharmacology principles to the rational use of drugs in clinical practice.
Oxidation: It is the most common type of drug metabolism involving the introduction of oxygen into a compound, usually catalyzed by enzymes known as cytochrome P450s.
Reduction: A process that reduces the size of a molecule by removing oxygen or adding electrons, often mediated by alcohol or aldehyde dehydrogenase enzymes.
Hydrolysis: The breakdown of a compound through the addition of water molecules, usually accomplished by enzymes known as esterases.
Conjugation: The addition of a small molecule (such as glucuronic acid, sulfate, or amino acid) to a drug or its metabolite to increase water-solubility, facilitate excretion, and decrease the toxicity.
Methylation: A process that adds a methyl group (CH3) to a molecule, which can affect the molecule's activity, bioavailability and toxicity.
Acetylation: The addition of an acetyl group (COCH3) to a molecule, usually catalyzed by enzymes known as acetyltransferases or NATs.
Dealkylation: The removal of an alkyl group (-CH2-CH3, -CH(CH3)2, or -CH2Ph) from a molecule, often catalyzed by cytochrome P450 enzymes.
Amination: The addition of an amino group (-NH2) or transfer of an amino group from one molecule to another, often catalyzed by transamination reactions or amidases.
Glycosylation: A type of conjugation where a sugar molecule is added to a molecule, mainly catalyzed by glycosyltransferases.
Esterification: A type of conjugation where a molecule is combined with an alcohol to form an ester.
"Drug metabolism is the metabolic breakdown of drugs by living organisms, usually through specialized enzymatic systems."
"Xenobiotic metabolism is the set of metabolic pathways that modify the chemical structure of xenobiotics, which are compounds foreign to an organism's normal biochemistry, such as any drug or poison."
"These pathways are a form of biotransformation present in all major groups of organisms and are considered to be of ancient origin."
"These reactions often act to detoxify poisonous compounds (although in some cases the intermediates in xenobiotic metabolism can themselves cause toxic effects)."
"The study of drug metabolism is called pharmacokinetics. The rate of metabolism determines the duration and intensity of a drug's pharmacologic action."
"Drug metabolism also affects multidrug resistance in infectious diseases and in chemotherapy for cancer."
"The actions of some drugs as substrates or inhibitors of enzymes involved in xenobiotic metabolism are a common reason for hazardous drug interactions."
"These pathways are also important in environmental science, with the xenobiotic metabolism of microorganisms determining whether a pollutant will be broken down during bioremediation, or persist in the environment."
"The enzymes of xenobiotic metabolism, particularly the glutathione S-transferases are also important in agriculture, since they may produce resistance to pesticides and herbicides."
"Drug metabolism is divided into three phases."
"In phase I, enzymes such as cytochrome P450 oxidases introduce reactive or polar groups into xenobiotics."
"These modified compounds are then conjugated to polar compounds in phase II reactions. These reactions are catalysed by transferase enzymes such as glutathione S-transferases."
"Finally, in phase III, the conjugated xenobiotics may be further processed."
"…before being recognized by efflux transporters and pumped out of cells."
"Drug metabolism often converts lipophilic compounds into hydrophilic products that are more readily excreted." Please note that while the provided quotes answer the questions, they are partial quotes and not complete sentences from the original paragraph.