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Related Concept Videos

Factors Affecting Drug Biotransformation: Biological01:19

Factors Affecting Drug Biotransformation: Biological

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Biological factors significantly impact drug metabolism, influencing drug clearance, efficacy, and potential toxicity.
Species differences: Variations in enzyme systems across species can cause disparities in drug metabolism. For instance, humans may metabolize certain drugs faster than rodents, altering therapeutic effects.
Strain differences: Genetic variations within a species can result in differing enzyme activity, impacting drug response and toxicity. For example, some mouse strains may...
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Factors Affecting Drug Biotransformation: Physicochemical and Chemical Properties of Drugs01:21

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A drug's physicochemical properties fundamentally influence its metabolism. For instance, a drug's molecular size and shape critically determine its interaction with enzymes and transporters — larger drugs may face difficulty reaching enzyme active sites, altering their metabolic pathways. The pKa of a drug, which establishes its ionization state, can impact its solubility and absorption, thereby influencing metabolism.
The drug's acidity or basicity is essential in...
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Phase II Reactions: Methylation Reactions01:17

Phase II Reactions: Methylation Reactions

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Methylation is a phase II biotransformation process involving the attachment of a methyl group to a substrate. Enzymes known as methyltransferases orchestrate this reaction.
The mechanism of methylation unfolds in two stages. The first stage sees a methyltransferase enzyme facilitating the transfer of a methyl group from S-adenosylmethionine (SAM) to the substrate, forming S-adenosylhomocysteine (SAH). The second stage involves further metabolism of SAH into homocysteine, which can be recycled...
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Nonlinear Pharmacokinetics: Dependence of Elimination Half-Life and Dose Clearance01:23

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The elimination half-life and drug clearance of drugs following nonlinear kinetics can vary with dosage. The Michaelis-Menten parameters and drug concentration influence these factors. As the dose increases, the elimination half-life tends to lengthen, resulting in a reduction in clearance and a disproportionately larger area under the curve. The total clearance can be derived from the Michaelis-Menten equation for drugs following a one-compartment model.
A study on guinea pigs examined the...
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Drug Metabolism: Phase I Reactions01:17

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A phase I reaction is a biochemical process that introduces a functionally reactive polar group to a substance. This transformation predominantly occurs in the liver, facilitated by the cytochrome P450 system of hemoproteins situated in the lipophilic endoplasmic reticulum of cells. The metabolite generated through this process can have varying polarities. If it is sufficiently polar, it can be easily excreted in the urine due to its water compatibility. However, if the metabolite is nonpolar,...
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Pharmaceutical substances known as xenobiotics are predominantly lipophilic and nonionized. This enables them to permeate lipid bilayers, such as cell membranes, and interact with intracellular target receptors. Lipophilic drugs have an advantage in crossing biological barriers and reaching their intended sites of action. However, lipophilic drugs often have a restricted capacity for renal expulsion or elimination from the body. When these drugs enter the kidneys and undergo glomerular...
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Effects of CYP3A4 Variants on Methadone Metabolism In Vitro.

Chen-Chen Wang1, Ming-Lei Zhang1, Yan-Dan Xu1

  • 1Department of Pharmacy, Quzhou KeCheng People's Hospital, Quzhou, Zhejiang, China.

Biomedical Chromatography : BMC
|December 4, 2024
PubMed
Summary

Cytochrome P450 (CYP450) gene variations impact methadone metabolism. This study evaluated 22 CYP3A4 variants, finding 12 decreased and 3 increased methadone

Keywords:
CYP3A4 variantsdrug‐metabolizing enzymegenetic polymorphismsintrinsic clearancemethadone metabolism

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Area of Science:

  • Pharmacogenomics
  • Drug Metabolism
  • Enzyme Kinetics

Background:

  • Cytochrome P450 (CYP450) enzymes, especially CYP3A4, are crucial for hepatic drug metabolism, processing over half of all drugs.
  • Methadone is extensively metabolized by CYP450 enzymes, making its metabolism susceptible to genetic variations.

Purpose of the Study:

  • To evaluate the catalytic efficiency of 22 CYP3A4 allelic variants on the in vitro oxidative metabolism of methadone.
  • To understand how CYP3A4 gene polymorphisms influence methadone's N-demethylation and intrinsic clearance.

Main Methods:

  • Utilized a baculovirus-insect cell expression system to produce recombinant CYP3A4 variants.
  • Assessed the N-demethylation activity of methadone by wild-type (CYP3A4*1) and variant CYP3A4 enzymes.
  • Quantified intrinsic clearance of methadone for each variant.

Main Results:

  • Twelve CYP3A4 variants showed significantly lower intrinsic clearance of methadone compared to the wild type.
  • Three CYP3A4 variants exhibited significantly increased intrinsic clearance of methadone.
  • Six variants showed no significant difference, and one variant had undetectable expression.

Conclusions:

  • CYP3A4 gene polymorphisms significantly alter methadone's metabolic clearance.
  • Understanding these variations can guide personalized methadone therapy and link genetic profiles to clinical outcomes.