Metabolism and Excretion of Drugs: Key Concepts and Enzymes
What is drug metabolism? - correct answer The biotransformation of drugs, where enzymes
cause a chemical change to the drug molecule, either building it up or breaking it down.
What are the two main processes involved in drug elimination? - correct answer Metabolism
and excretion.
How does metabolism affect a drug's ability to move around the body? - correct answer
Altering the chemical structure of the drug often makes it easier to excrete or changes its
effects by affecting its ability to bind to receptors.
What are the possible outcomes of drug metabolism? - correct answer 1. Termination of drug
activity. 2. Increased drug activity (activation of prodrugs). 3. No change in activity (metabolite
is also biologically active). 4. Production of toxic or carcinogenic metabolites.
What is an example of a prodrug and its active form? - correct answer Acetylsalicylic acid
(aspirin) is converted to salicylate, its active derivative.
What happens when paracetamol is metabolized? - correct answer It can produce NAPQI, a
very toxic metabolite, especially in cases of overdose.
Where is the major site of drug metabolism? - correct answer The liver.
What role do CYP450 enzymes play in drug metabolism? - correct answer They are involved in
drug metabolism in the intestinal wall.
What are some sites of drug metabolism besides the liver? - correct answer Intestinal wall, GI
tract (gut bacteria and proteases), plasma (esterases), and lungs.
What are the four main types of metabolism reactions? - correct answer 1. Oxidation. 2.
Reduction. 3. Hydrolysis. 4. Conjugation.
What occurs during oxidation in drug metabolism? - correct answer An increase in the
proportion of oxygen on the molecule.
What is hydrolysis in the context of drug metabolism? - correct answer The addition of a water
molecule to a compound, usually resulting in bond cleavage.
What is conjugation in drug metabolism? - correct answer The addition of an endogenous
substrate, which usually increases molecular mass, polarity, and water solubility.
Why is conjugation important for drug excretion? - correct answer It makes the drug more
polar and water-soluble, facilitating easier excretion.
What factors are required for enzymatic metabolism to occur? - correct answer The substrate,
enzyme, and any co-factors must be in high supply.
, How can enzymatic metabolism occur? - correct answer It may occur sequentially, may
compete, or may not occur at all; it is opportunistic.
What is the effect of liver enzymes on oral drug bioavailability? - correct answer Enzymes in the
liver and gut wall influence the amount of oral drug that gets into the bloodstream.
What is the role of esterase in drug metabolism? - correct answer Esterases are involved in
prodrug activation and metabolism within the plasma.
What is the significance of gut bacteria in drug metabolism? - correct answer They contribute
to metabolism in the GI tract.
What happens to the detoxification capacity of the liver during a paracetamol overdose? -
correct answer It becomes overwhelmed, leading to a dangerous increase in the concentration
of NAPQI.
What is the relationship between drug metabolism and drug activity? - correct answer
Metabolism often terminates drug activity but can also increase activity or produce toxic
metabolites.
What is the primary function of drug metabolism? - correct answer To alter the chemical
structure of drugs for elimination and to potentially activate prodrugs.
What three components are needed for a reaction in phase I and II metabolism? - correct
answer A substrate, an enzyme, and a co-factor.
What is the role of a co-factor in enzyme reactions? - correct answer To activate the enzyme.
What type of reaction does Phase 1 metabolism typically involve? - correct answer Oxidation.
What type of reaction does Phase 2 metabolism typically involve? - correct answer Conjugation.
What is the most important family of oxidative enzymes involved in drug metabolism? - correct
answer The CYP450 family.
Where are CYP450 enzymes mainly located? - correct answer On the smooth endoplasmic
reticulum and some around the mitochondria.
Name two other enzymes that can catalyze oxidation besides CYP450. - correct answer Alcohol
dehydrogenase and aldehyde dehydrogenase.
What are the five features of CYP450 oxidation? - correct answer 1. Substrate binding 2.
Oxygen binding 3. Oxygen splitting 4. Inserting oxygen into substrate 5. Release of the
metabolite.
What is the significance of the P450 reference in CYP nomenclature? - correct answer It refers
to the wavelength detected during HPLC at 450 nm.
What is drug metabolism? - correct answer The biotransformation of drugs, where enzymes
cause a chemical change to the drug molecule, either building it up or breaking it down.
What are the two main processes involved in drug elimination? - correct answer Metabolism
and excretion.
How does metabolism affect a drug's ability to move around the body? - correct answer
Altering the chemical structure of the drug often makes it easier to excrete or changes its
effects by affecting its ability to bind to receptors.
What are the possible outcomes of drug metabolism? - correct answer 1. Termination of drug
activity. 2. Increased drug activity (activation of prodrugs). 3. No change in activity (metabolite
is also biologically active). 4. Production of toxic or carcinogenic metabolites.
What is an example of a prodrug and its active form? - correct answer Acetylsalicylic acid
(aspirin) is converted to salicylate, its active derivative.
What happens when paracetamol is metabolized? - correct answer It can produce NAPQI, a
very toxic metabolite, especially in cases of overdose.
Where is the major site of drug metabolism? - correct answer The liver.
What role do CYP450 enzymes play in drug metabolism? - correct answer They are involved in
drug metabolism in the intestinal wall.
What are some sites of drug metabolism besides the liver? - correct answer Intestinal wall, GI
tract (gut bacteria and proteases), plasma (esterases), and lungs.
What are the four main types of metabolism reactions? - correct answer 1. Oxidation. 2.
Reduction. 3. Hydrolysis. 4. Conjugation.
What occurs during oxidation in drug metabolism? - correct answer An increase in the
proportion of oxygen on the molecule.
What is hydrolysis in the context of drug metabolism? - correct answer The addition of a water
molecule to a compound, usually resulting in bond cleavage.
What is conjugation in drug metabolism? - correct answer The addition of an endogenous
substrate, which usually increases molecular mass, polarity, and water solubility.
Why is conjugation important for drug excretion? - correct answer It makes the drug more
polar and water-soluble, facilitating easier excretion.
What factors are required for enzymatic metabolism to occur? - correct answer The substrate,
enzyme, and any co-factors must be in high supply.
, How can enzymatic metabolism occur? - correct answer It may occur sequentially, may
compete, or may not occur at all; it is opportunistic.
What is the effect of liver enzymes on oral drug bioavailability? - correct answer Enzymes in the
liver and gut wall influence the amount of oral drug that gets into the bloodstream.
What is the role of esterase in drug metabolism? - correct answer Esterases are involved in
prodrug activation and metabolism within the plasma.
What is the significance of gut bacteria in drug metabolism? - correct answer They contribute
to metabolism in the GI tract.
What happens to the detoxification capacity of the liver during a paracetamol overdose? -
correct answer It becomes overwhelmed, leading to a dangerous increase in the concentration
of NAPQI.
What is the relationship between drug metabolism and drug activity? - correct answer
Metabolism often terminates drug activity but can also increase activity or produce toxic
metabolites.
What is the primary function of drug metabolism? - correct answer To alter the chemical
structure of drugs for elimination and to potentially activate prodrugs.
What three components are needed for a reaction in phase I and II metabolism? - correct
answer A substrate, an enzyme, and a co-factor.
What is the role of a co-factor in enzyme reactions? - correct answer To activate the enzyme.
What type of reaction does Phase 1 metabolism typically involve? - correct answer Oxidation.
What type of reaction does Phase 2 metabolism typically involve? - correct answer Conjugation.
What is the most important family of oxidative enzymes involved in drug metabolism? - correct
answer The CYP450 family.
Where are CYP450 enzymes mainly located? - correct answer On the smooth endoplasmic
reticulum and some around the mitochondria.
Name two other enzymes that can catalyze oxidation besides CYP450. - correct answer Alcohol
dehydrogenase and aldehyde dehydrogenase.
What are the five features of CYP450 oxidation? - correct answer 1. Substrate binding 2.
Oxygen binding 3. Oxygen splitting 4. Inserting oxygen into substrate 5. Release of the
metabolite.
What is the significance of the P450 reference in CYP nomenclature? - correct answer It refers
to the wavelength detected during HPLC at 450 nm.
