Difference Between Phase I And Phase Ii Drug Metabolism Pdf

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17.05.2021 at 20:32
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difference between phase i and phase ii drug metabolism pdf

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Breast cancer is a complex disease which is provoked by a multitude of exogenous and endogenous factors including genetic variations. Recent genome-wide association studies identified a set of more than 18 novel low penetrant susceptibility loci, however, a limitation of this powerful approach is the hampered analysis of polymorphisms in DNA sequences with a high degree of similarity to other genes or pseudo genes. Since this common feature affects the majority of the highly polymorphic genes encoding phase I and II enzymes the retrieval of specific genotype data requires adapted amplification methods.

Topics on Drug Metabolism. All organisms are constantly and unavoidably exposed to xenobiotics including both man—made and natural chemicals such as drugs, plant alkaloids, microorganism toxins, pollutants, pesticides, and other industrial chemicals. Formally, biotransformation of xenobiotics as well as endogenous compounds is subdivided into phase I and phase II reactions.

Drug metabolism

Commonly there are four types of reactions involved in drug metabolism. These are: oxidation reduction hydrolysis conjugation The first three are often lumped together as phase I reactions, while the fourth process, conjugation, is called phase II metabolism. A common scheme in the overall metabolism of drugs is that metabolites are metabolized. In particular a drug may be oxidized, reduced or hydrolyzed and then another group may be added in a conjugation step. A common cause of capacity limited metabolism is a limit in the amount of the conjugate added in the conjugation step. Phase 0 Phase 0 has been described as the transport of drug from the blood into the heptacytes in the liver, the basolateral sinusoidal uptake processes see Chapter 11 Ishikawa, Although not included in the Phase 0 designation, absorption of drugs from the intestinal lumen to the portal blood supply involves transport and metabolism enzyme processes.

Introduction to Drug Metabolism pp Cite as. The routes by which drugs may be metabolised or biotransformed are many and varied and include the chemical reactions of oxidation, reduction, hydrolysis, hydration, conjugation and condensation. It is important that these pathways are studied as the route of metabolism of a drug can determine whether it shows any pharmacological or toxicological activity. Drug metabolism is normally divided into two phases, phase I or functionalisation reactions and phase II or conjugative reactions. The chemical reactions normally associated with phase I and phase II drug metabolism are given in Table 1. Unable to display preview. Download preview PDF.

Phase I biotransformation reactions introduce or expose functional groups on the drug with the goal of increasing the polarity of the compound. Although Phase I drug metabolism occurs in most tissues, the primary and first pass site of metabolism occurs during hepatic circulation. Additional metabolism occurs in gastrointestinal epithelial, renal, skin, and lung tissues. Within cells, most phase I enzymes are located in the endoplasmic reticulum and thus are enriched in microsomal preparations. Phase I reactions are broadly grouped into three categories, oxidation, reduction, and hydrolysis. As most small molecule drugs are lipophilic in nature, drug metabolism converts these hydrophobic compounds into more water soluble compounds that can be excreted.

Pathways of drug metabolism

The liver is the principal site of drug metabolism for review, see [ 1 ]. Although metabolism typically inactivates drugs, some drug metabolites are pharmacologically active—sometimes even more so than the parent compound. An inactive or weakly active substance that has an active metabolite is called a prodrug, especially if designed to deliver the active moiety more effectively. Drugs can be metabolized by oxidation, reduction, hydrolysis, hydration, conjugation, condensation, or isomerization; whatever the process, the goal is to make the drug easier to excrete. The enzymes involved in metabolism are present in many tissues but generally are more concentrated in the liver.

Phase I Drug Metabolism

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Drug metabolism is the metabolic breakdown of drugs by living organisms , usually through specialized enzymatic systems. More generally, xenobiotic metabolism from the Greek xenos "stranger" and biotic "related to living beings" 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.

Drug Metabolism

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Victoire G.
19.05.2021 at 13:31 - Reply

drugs into compounds which are easier to eliminate. The Metabolism is often divided into two phases: Phase three possible results of phase 1 metabolism.

23.05.2021 at 15:55 - Reply

This results in activation or inactivation of the parent drug. Phase II metabolism. Phase II reactions involve conjugation of the drug with endogenous charged.

Onan S.
25.05.2021 at 01:24 - Reply

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Karolin F.
26.05.2021 at 21:53 - Reply

Phase I reactions of drug metabolism involve oxidation, reduction, or hydrolysis of the parent drug, resulting in its conversion to a more polar molecule. Phase II reactions involve conjugation by coupling the drug or its metabolites to another molecule, such as glucuronidation, acylation, sulfate, or glicine.

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