PRELIM 02 - Metabolic Changes of Drugs Flashcards
The process by which the drug is chemically converted in the body to a metabolite
Drug metabolism
Refers to the formation of inactive and relatively nontoxic compounds
Detoxification
Main site of drug metabolism
Liver
The first pass effect __________ bioavailability
Decreases
Effect wherein drugs are metabolized before they are distributed to the rest of the body
First pass effect
Effect that involves the rapid metabolism of an orally administered drug before reaching the general circulation
First pass effect
The most important enzyme system affecting drug metabolism
CYP450 enzyme system
Cytochrome P450 enzymes are involved in __________
Oxidative biotransformation
Cytochrome P450 enzymes are __________
Monooxygenases
Caffeine, testosterone, R-warfarin (CYP enzyme)
1A1
Acetaminophen, caffeine, phenacetin, R-warfarin (CYP enzyme)
1A2
17β-estradiol, testosterone (CYP enzyme)
2A6
Cyclophosphamide, erythromycin, testosterone (CYP enzyme)
2B6
Acetaminophen, tolbutamide, hexobarbital, S-warfarin, phenytoin, testosterone, R-warfarin, zidovudine (CYP enzyme)
2C-family
Acetaminophen, caffeine, chlorzoxazone, halothane (CYP enzyme)
2E1
Acetaminophen, codeine, debrisoquine (CYP enzyme)
2D6
Acetaminophen, caffeine, carbamazepine, codeine, cortisol, erythromycin, cyclophosphamide, S- and R-warfarin, phenytoin, testosterone, halothane, zidovudine (CYP enzyme)
3A4
2 phases of drug metabolism
Phase I, Phase II
Phase I is also known as __________
Functionalization reactions
Oxidation of aromatic moieties (Phase of drug metabolism)
Phase I (Functionalization reaction)
Oxidation of olefins (Phase of drug metabolism)
Phase I (Functionalization reaction)
Oxidation of benzylic, allylic carbon atoms, and carbon atoms to carbonyl and imines (Phase of drug metabolism)
Phase I (Functionalization reaction)
Oxidation involving carbon-heteroatom systems (Phase of drug metabolism)
Phase I (Functionalization reaction)
Oxidation of alcohols and aldehydes (Phase of drug metabolism)
Phase I (Functionalization reaction)
Other miscellaneous oxidative reactions (Phase of drug metabolism)
Phase I (Functionalization reaction)
Reduction of aldehydes and ketones (Phase of drug metabolism)
Phase I (Functionalization reaction)
Reduction of nitro and azo compounds (Phase of drug metabolism)
Phase I (Functionalization reaction)
Miscellaneous reductive reactions (Phase of drug metabolism)
Phase I (Functionalization reaction)
Hydrolysis of esters and amides (Phase of drug metabolism)
Phase I (Functionalization reaction)
Hydration of epoxides and arene oxides by epoxide hydrase (Phase of drug metabolism)
Phase I (Functionalization reaction)
Phase II reaction is also known as __________
Conjugation reactions
Glucuronic acid conjugation (Phase of drug metabolism)
Phase II (Conjugation reaction)
Sulfate conjugation (Phase of drug metabolism)
Phase II (Conjugation reaction)
Conjugation with glycine, glutamine, and other amino acids (Phase of drug metabolism)
Phase II (Conjugation reaction)
Glutathione or mercapturic acid conjugation (Phase of drug metabolism)
Phase II (Conjugation reaction)
Acetylation (Phase of drug metabolism)
Phase II (Conjugation reaction)
Methylation (Phase of drug metabolism)
Phase II (Conjugation reaction)
Involves the introduction of a functional polar group by direct introduction or modification/unmasking (Phase of drug metabolism)
Phase I (Functionalization reaction)
4 functional polar groups (OCNS)
OH, COOH, NH2, SH
__________ involves the direct introduction of functional group (Examples of Phase I reactions)
Hydration
__________, __________, and __________ involves modifying or unmasking existing functional groups (Examples of Phase I reactions) (ORH)
Oxidation, Reduction, Hydrolysis
Involves the conjugation or attachment of small, polar, and ionization endogenous compounds (Phase of drug metabolism)
Phase II (Conjugation reaction)
Phase II (Conjugation reactions) are catalyzed by __________
Transferase enzymes
Is the most common conjugative pathway in drug metabolism due to readily available supply of D-glucuronic acid (Examples of Phase II reactions)
Glucuronidation
In infants and young children, the __________ conjugate is the main urinary product
O-sulfate
Involves the conjugation of xenobiotics with sulfate (Examples of Phase II reactions)
Sulfonation/Sulfate conjugation
Conjugation of xenobiotics with sulfate occurs primarily with __________
Phenols
The sulfate conjugation process involves the activation of inorganic sulfate to the coenzyme __________
3-phosphoadenosine-5-phosphosulfate (PAPS)
The amino acids __________ and __________ are used to conjugate carboxylic acids (GG)
Glycine, Glutamine
The amino acids glycine and glutamine are used to conjugate __________
Carboxylic acids
__________ conjugation is common to most animals
Glycine
__________ conjugation appears to be confined mainly to humans and other primates
Glutamine
Takes place in most cells; important in detoxifying potentially dangerous environmental toxins (Examples of Phase II reactions)
Glutathione conjugation
Xenobiotics conjugated with GSH undergo further biotransformation to give S-substituted N-acetylcysteine products called __________
Mercapturic acids
Its main function is to terminate pharmacological activity and detoxification (Examples of Phase II reactions)
Acetylation
This variation is genetic and is caused mainly by differences in N-acetyltransferase activity
Acetylation polymorphism
__________ and __________ are rapid acetylators (EA)
Eskimos, Asians
__________ and some __________ groups are mainly slow acetylators (EW)
Egyptians, Western European
Is important in the biosynthesis of many endogenous compounds and in the inactivation of numerous physiologically active biogenic amines (Examples of Phase II reactions)
Methylation
The coenzyme involved in methylation reactions is __________
S-Adenosylmethionine (SAM)
Women are __________ ethanol metabolizers than men
Slower
Biotransformation time of phenylbutazone in rabbits
3 hours
Biotransformation time of phenylbutazone in horses
6 hours
Biotransformation time of phenylbutazone in monkeys
8 hours
Biotransformation time of phenylbutazone in mice
18 hours
Biotransformation time of phenylbutazone in man
36 hours
Caucasians are __________ acetylators
Slow
Meaning of NAPQI (a toxic byproduct of paracetamol metabolism)
N-acetyl-para-benzo-quinone imine
Antidote for paracetamol overdose
N-acetylcysteine