Glossary of Med Chem: Drug Metabolism
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- Define xenobiotics
- Drugs and other substances foreign to the body
- Where does metabolism of xenobiotics take place?
- primarily in the hepatocytes of the liver (through the action of enzymes)
- What is the major site of extrahepatic metabolism?
(kidney, lungs and skin are minor)
- Where are most drugs metabolized?
- Enzymes modify the parent structure to a more ___________ product.
- Define metabolic pathways
- Various routes that a drug can take on its way to being enzymatically INACTIVATED and EXCRETED
- In a compound, how many phase I reactions can occur? Phase II reactions?
- Phase I: One or more
Phase II: only ONE
- What are the 2 main goals of metabolism?
- -Increased water solubility
-Enhanced rate of elimination
- What are the four possible effects on drug action?
-Bioactivation (of prodrugs)
- Explain first pass metabolism
- Drugs given orally are metabolized extensively in the liver (hepatic-portal vein) before reaching the general circulation
**This leads to decreased bioavailability**
- Explain prehepatic metabilism
- Refers to drug metabolism conducted by enzymes in the gut (before it ever reaches the liver)
- Name a classic inducer of CYP 450.
- Phenobarbital (Barbiturates)
(inducers - over metabolize - less effect)
- Name a classic inhibitor of CYP 450
(inhibitors - less metabolizing - toxicity)
- What happens when CYP 450 is induced?
- The drug is over metabolized leading to enhanced elimination and less therapeutic effect
- What happens when CYP 450 is inhibited?
- It keeps the drug from metabolizing leading to less elimination and toxicity
- What is a unique inhibitor of CYP 3A4?
- Grapefruit juice
- What are some factors that influence metabolism?
- -age, gender, nutrition, disease, race/ethnicity
-drug/drug and drug/food interactions
- What are the three types of Phase I reactions?
- What is another name for Phase II reactions?
- Conjugation reactions
- What is the main enzyme family in oxidations?
- What does the CYP450 system do?
- chemically inserts a single oxygen atom into their substrates
- CYP450 metabolism requires four things:
- 1. A heme protein
4. Molecular Oxygen
- CYP450 is in a resting state when bound to _____ and in an active state when bound to _____.
- Fe3+ (oxidized); Fe2+ (reduced)
- What is the primary phase I reaction?
(then reductions then hydrolyses)
- What is genetic polymorphism?
- When a racial group does not metabolize drugs well
-poor metabolizers can lead to reduced therapeutic effect
-ultrafast metabolizers can lead to toxicity
- Where does Hydroxylation take place?
- Aromatic rings, non-aromatic rings and carbon chains
- In phenyl rings where does hydroxylation take place?
- Primarily at the Para-position (if it is not blocked by a substituent)
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