What is first phase metabolism?

Phase 1 metabolism involves chemical reactions such as oxidation (most common), reduction and hydrolysis. There are three possible results of phase 1 metabolism. The drug becomes completely inactive. … One or more of the metabolites are pharmacologically active, but less so than the original drug.

What are the 3 phases of metabolism?

The metabolism of xenobiotics is often divided into three phases:- modification, conjugation, and excretion.

What is the difference between Phase 1 and Phase 2 metabolism?

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.

Where does phase 1 metabolism occur?

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.

What are the 2 phases of metabolism?

Metabolism is often divided into two phases of biochemical reaction – phase 1 and phase 2. Some drugs may undergo just phase 1 or just phase 2 metabolism, but more often, the drug will undergo phase 1 and then phase 2 sequentially.

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What is Phase 1 xenobiotic metabolism?

Metabolism is often divided into two phases: Phase 1 metabolism involves chemical reactions such as oxidation (most common), reduction and hydrolysis. There are three possible results of phase 1 metabolism. The drug becomes completely inactive. In other words, the metabolites are pharmacologically inactive.

What is oxidation in phase 1 metabolism?

Oxidation – (Figure 1) Oxidation reactions are some of the most common xenobiotic transformations occurring in plants. These Phase I reactions result in either detoxication or activation of the herbicide. and the atom is reduced to water by an electron donor, such as NADPH (equation 1). …

Where does Phase 2 of drug metabolism occur?

Glucuronidation, the most common phase II reaction, is the only one that occurs in the liver microsomal enzyme system. Glucuronides are secreted in bile and eliminated in urine. Thus, conjugation makes most drugs more soluble and easily excreted by the kidneys.

What are the phases of drug metabolism?

Drug metabolism reactions comprise of two phases: Phase I (functionalization) reactions such as oxidation, hydrolysis; and Phase II (conjugation) reactions such as glucuronidation, sulphate conjugation. Oxidation reactions are the most common and vital.

Does Phase 2 metabolism occur in the liver?

The liver is the primary site for metabolism. Liver contains the necessary enzymes for metabolism of drugs and other xenobiotics. These enzymes induce two metabolism pathways: Phase I (functionalization reactions) and Phase II (biosynthetic reactions) metabolism.

Is first pass metabolism the same as Phase 1?

Phase 1 reactions are often oxidations or hydrolysis reactions, although reductions also occur. In terms of first-pass metabolism in the liver – hydrolysis of pharmacologically inactive esters (prodrugs) to active drugs are important phase 1 reactions.

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What is Glucuronidation metabolism?

n. a metabolic process by which drugs or other substances are combined with glucuronic acid to form more water-soluble compounds, which are more readily excreted by the kidneys or in bile. Glucuronidation is the most prevalent of the Phase II reactions of drug metabolism. ADVERTISEMENT.

How does polarity affect metabolism?

Metabolism is the enzymatic conversion of one chemical compound into another. Overall, metabolic processes will convert the drug into a more water-soluble compound by increasing its polarity. … This is an essential step before the drug can be excreted in the body fluids such as urine or bile.

What are the 2 major goals of drug metabolism?

The purpose of metabolism in the body is usually to change the chemical structure of the substance, to increase the ease with which it can be excreted from the body. Drugs are metabolized through various reactions including: Oxidation. Reduction.

What is oxidation in metabolism?

Metabolic energy derives from processes of oxidation and reduction. When energy is consumed in a process, chemical energy is made available for synthesis of ATP as one atom gives up electrons (becomes oxidized) and another atom accepts electrons (becomes reduced).

What are the reactions under phase 1 metabolism?

Phase I metabolism consists of reduction, oxidation, or hydrolysis reactions. These reactions serve to convert lipophilic drugs into more polar molecules by adding or exposing a polar functional group such as -NH2 or -OH.

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