Question 1

Which of the following best describes the primary function of cytochrome P450 (CYP) enzymes in drug metabolism?

Accepted Answer

They catalyze oxidation reactions, introducing or exposing functional groups to increase drug solubility.

Question 2

A patient is prescribed a drug that is metabolized primarily by CYP2D6. Which factor is most likely to affect the rate of metabolism for this drug?

Accepted Answer

Genetic polymorphisms in CYP2D6

Question 3

Which phase I reaction is responsible for converting a primary alcohol group to an aldehyde, and which cofactor is required?

Accepted Answer

Alcohol dehydrogenase reaction; nicotinamide adenine dinucleotide (NAD+)

Question 4

St. John’s wort is known to induce CYP3A4. What is the likely consequence for a patient taking a drug metabolized by CYP3A4?

Accepted Answer

Decreased plasma concentration of the drug

Question 5

Which equation best represents the rate of drug metabolism as a function of enzyme concentration and substrate concentration, assuming Michaelis-Menten kinetics?

Accepted Answer

$$ v = \frac{V_{max} \cdot [S]}{K_m + [S]} $$

Question 6

A drug containing a nitro group undergoes reduction to form an amine. Which phase I reaction is this?

Accepted Answer

Reduction

Question 7

Which CYP family is primarily responsible for the metabolism of endogenous steroids?

Accepted Answer

CYP7, CYP11, CYP17, CYP19, CYP21, CYP27

Question 8

A patient is taking quinidine, which inhibits CYP2D6. What is the expected effect on a drug metabolized by CYP2D6?

Accepted Answer

Slower clearance and increased plasma concentration

Question 9

Which of the following is a common misconception about the role of CYP enzymes in drug metabolism?

Accepted Answer

CYP enzymes are involved in both phase I and phase II reactions.

Question 10

Which phase I reaction is illustrated by the conversion of 6-methylmercaptopurine to 6-mercaptopurine?

Accepted Answer

S-dealkylation

Question 11

Which factor is LEAST likely to affect the activity of drug-metabolizing enzymes?

Accepted Answer

Drug color and taste

Question 12

Which CYP family metabolizes the largest percentage of clinically used drugs?

Accepted Answer

CYP2

Question 13

A drug is metabolized by CYP2E1, which is induced in alcoholics. What is the likely effect of chronic alcohol consumption on the metabolism of this drug?

Accepted Answer

Increased metabolism and decreased drug concentration

Question 14

Which of the following reactions is NOT a typical phase I reaction?

Accepted Answer

Glucuronidation

Question 15

Which enzyme uses flavin-adenine dinucleotide (FAD) to create a peroxide during drug metabolism?

Accepted Answer

Flavin monooxygenase

Question 16

Which reaction is responsible for the conversion of an aldehyde to a carboxylic acid, and which cofactor is required?

Accepted Answer

Aldehyde dehydrogenase reaction; nicotinamide adenine dinucleotide (NAD+)

Question 17

Which CYP family is generally inducible and metabolizes polycyclic aromatic hydrocarbons?

Accepted Answer

CYP1

Question 18

A drug undergoes N-dealkylation during metabolism. What is the result of this reaction?

Accepted Answer

Removal of an alkyl group from a nitrogen atom

Question 19

Which of the following best describes the role of hydrolysis in drug metabolism?

Accepted Answer

Hydrolysis breaks down drugs by adding water to cleave ester or amide bonds.

Question 20

Which equation represents the conversion of a primary alcohol to an aldehyde by alcohol dehydrogenase?

Accepted Answer

$$ RCH_2OH + NAD^+ \rightarrow RCHO + NADH + H^+ $$

Drug Metabolism: Phase I Reactions and Cytochrome P450 Enzymes

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