Difference Between Phase I And Phase Ii Drug Metabolism Pdf

difference between phase i and phase ii drug metabolism pdf

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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.

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.

Drug Metabolism

NCBI Bookshelf. Simone Phang-Lyn ; Valerie A. Llerena 2. Biotransformation is a metabolic process that takes place mainly in the liver and helps to facilitate the excretion of both exogenous and endogenous substances. A series of reactions alter the chemical structures of these substances.

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. On the other hand, these conjugations also play an essential role in the toxicity of many chemicals due to the metabolic formation of toxic metabolites such as reactive electrophiles. Gene polymorphism of biotransformation enzymes may often play a role in various pathophysiological processes. Conjugation reactions usually involve metabolite activation by a high—energy intermediate and have been classified into two general types: type I e.

Phase I vs. Phase II Metabolism

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. With regard to breast cancer these genes are of certain interest due to their involvement in the metabolism of carcinogens like exogenous genotoxic compounds or steroid hormones. The present review summarizes the observed effects of functional genetic variants of phase I and II enzymes in well designed case control studies to shed light on their contribution to breast cancer risk. The implementation of cost effective high-throughput genotyping methods enables the determination of genotypes at large scale and fast pace.

If your institution subscribes to this resource, and you don't have a MyAccess Profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus. Please consult the latest official manual style if you have any questions regarding the format accuracy. All organisms are exposed to foreign chemical compounds xenobiotics in the air, water, and food. To ensure elimination of pharmacologically active xenobiotics as well as to terminate the action of many endogenous substances, evolution has provided metabolic pathways that alter their activity and their susceptibility to excretion. Many cells that act as portals for entry of external molecules into the body eg, pulmonary epithelium, intestinal epithelium contain transporter molecules MDR family [P-glycoproteins], MRP family, others that expel unwanted molecules immediately after absorption. However, some foreign molecules evade these gatekeepers and are absorbed. Therefore, all higher organisms, especially terrestrial animals, require mechanisms for ridding themselves of toxic foreign molecules after they are absorbed, as well as mechanisms for excreting undesirable substances produced within the body.

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. 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 metabolism of pharmaceutical drugs is an important aspect of pharmacology and medicine. For example, the rate of metabolism determines the duration and intensity of a drug's pharmacologic action.

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

Chapter 17

В перерывах между сигналами Сьюзан выкрикнула: - Ты - Северная Дакота, Энсей Танкадо передал тебе копию ключа. Он нужен мне немедленно. - Ты сошла с ума! - крикнул в ответ Хейл.  - Я вовсе не Северная Дакота! - И он отчаянно забился на полу. - Не лги, - рассердилась Сьюзан.

Drug metabolism

Ее основная работа в последние три года заключалась в тонкой настройке самого секретного компьютера в мире: большая часть программ, обеспечивавших феноменальное быстродействие ТРАНСТЕКСТА, была ее творением. Шифр в миллион бит едва ли можно было назвать реалистичным сценарием. - Ладно, - процедил Стратмор.  - Итак, даже в самых экстремальных условиях самый длинный шифр продержался в ТРАНСТЕКСТЕ около трех часов.

 Я все сотру перед уходом, - пообещала.  - Если только вы с женой не захотите сохранить этот фильм для своей частной коллекции. - Делай свою распечатку и выметайся! - зарычал. - Si, senor, - засмеявшись, ответила Мидж с подчеркнутым пуэрто-риканским акцентом и, подмигнув Бринкерхоффу, направилась к двойной двери директорского кабинета. Личный кабинет Лиланда Фонтейна ничем не походил на остальные помещения дирекции. В нем не было ни картин, ни мягкой мебели, ни фикусов в горшках, ни антикварных часов.

Polymorphisms of phase I and phase II enzymes and breast cancer risk


Robert L.


The liver is the principal site of drug metabolism for review, see [ 1 ].



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Somerville R.


Phase I biotransformation reactions introduce or expose functional groups on the drug with the goal of increasing the polarity of the compound.