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.
Where does Phase 2 metabolism occur?
Conjugation. 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 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.
Do all drugs undergo Phase 1 and Phase 2 metabolism?
This is called conjugation and the product is called a conjugate. Metabolites formed in phase 2 are unlikely to be pharmacologically active. Some drugs undergo either phase 1 or phase 2 metabolism, but most undergo phase 1 metabolism followed by phase 2 metabolism.
What are the two 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.
What is involved in Phases I and II of biotransformation?
The first phase involves oxidations, reductions or hydrolyses or a combination of any of these three, and for convenience these may be termed “phase I reactions”; the second phase (“phase II reactions”) consists of synthesis, mainly conjugations such as glucuronide, ethereal sulphate, thiocyanate, and hippuric acid …
What are the two routes by which drugs can be eliminated into the system?
Renal excretion is the most common route of drug elimination. However, many drugs are excreted into bile via the liver and some volatile substances (primarily gaseous anesthetics) can be excreted via the lungs.
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.
What is a Phase 1 reaction?
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. Typically, oxidation is the most common phase I reaction.
What happens if a drug is not metabolized?
The substances that result from metabolism (metabolites) may be inactive, or they may be similar to or different from the original drug in therapeutic activity or toxicity. Some drugs, called prodrugs, are administered in an inactive form, which is metabolized into an active form.
What is second pass metabolism?
GC -> Liver. Second-pass metabolism is where the drug comes back to the liver from the circulation.
Does a fast metabolism affect medication?
If your body metabolizes a drug too quickly, you may not get any benefit from the prescribed dose. Your dose may need to be increased to reach a therapeutic effect.
Is Glucuronidation a Phase 2?
Glucuronidation is a well-characterized phase II metabolic pathway that has high capacity and provides rapid drug inactivation via the polar glucuronide metabolites produced.
What is the difference between biotransformation and metabolism?
Biotransformation is the process by which a substance changes from one chemical to another (transformed) by a chemical reaction within the body. Metabolism or metabolic transformations are terms frequently used for the biotransformation process.
What is Glucuronidation metabolism?
Glucuronidation involves the metabolism of parent compound by UDP-glucuronosyltransferases (UGTs) into hydrophilic and negatively charged glucuronides that cannot exit the cell without the aid of efflux transporters.22 мая 2017 г.
What are the factors affecting metabolism?
Your metabolic rate is influenced by many factors – including age, gender, muscle-to-fat ratio, amount of physical activity and hormone function.