Drug biotransformation, or drug metabolism, is a core pharmacological concept that affects drug efficacy, duration of action, and toxicity. It involves enzymatic conversion of drugs to more water-soluble metabolites for easier excretion. This quiz, based on Pharm.D. coursework (e.g., PHA5439, PHA5515, PHA5176), tests your understanding of metabolic pathways, enzymes, and clinical implications.
1. What is the primary site of drug biotransformation in the body?
- A. Kidney
- B. Small intestine
- C. Liver
- D. Lungs
Correct answer: C. Liver
2. The term “first-pass effect” refers to:
- A. Drug filtration in the kidney
- B. Drug metabolism in the intestinal wall
- C. Drug metabolism during its first pass through the liver
- D. Rapid onset of drug action
Correct answer: C. Drug metabolism during its first pass through the liver
3. Which of the following is a Phase I reaction?
- A. Glucuronidation
- B. Acetylation
- C. Oxidation
- D. Sulfation
Correct answer: C. Oxidation
4. The most important enzyme family in Phase I metabolism is:
- A. UDP-glucuronosyltransferases
- B. Glutathione S-transferases
- C. Cytochrome P450
- D. Esterases
Correct answer: C. Cytochrome P450
5. Which of the following processes is typical of Phase II reactions?
- A. Hydrolysis
- B. Oxidation
- C. Conjugation
- D. Reduction
Correct answer: C. Conjugation
6. Which enzyme is primarily responsible for glucuronidation?
- A. CYP3A4
- B. UGT
- C. MAO
- D. COMT
Correct answer: B. UGT
7. A prodrug is designed to:
- A. Decrease drug absorption
- B. Inhibit metabolism
- C. Be metabolized into an active compound
- D. Act faster than the parent drug
Correct answer: C. Be metabolized into an active compound
8. Which cytochrome P450 isoform metabolizes the largest proportion of clinically used drugs?
- A. CYP1A2
- B. CYP2D6
- C. CYP3A4
- D. CYP2C9
Correct answer: C. CYP3A4
9. Which of the following is an example of Phase I reduction?
- A. Azo reduction
- B. Hydroxylation
- C. Demethylation
- D. Epoxidation
Correct answer: A. Azo reduction
10. An example of a Phase II sulfation reaction involves the enzyme:
- A. SULT
- B. CYP2E1
- C. UGT
- D. MAO
Correct answer: A. SULT
11. What is the primary goal of drug metabolism?
- A. Enhance taste of medication
- B. Convert drug to lipophilic form
- C. Convert drug to more water-soluble form for excretion
- D. Store drug in tissues
Correct answer: C. Convert drug to more water-soluble form for excretion
12. Which of the following does NOT typically undergo Phase II metabolism?
- A. Glucuronide conjugation
- B. Methylation
- C. Sulfation
- D. Hydrolysis
Correct answer: D. Hydrolysis
13. Which factor can significantly affect drug metabolism?
- A. Food temperature
- B. Patient’s genotype
- C. Storage container
- D. Capsule color
Correct answer: B. Patient’s genotype
14. Acetaminophen toxicity is largely due to:
- A. Sulfation
- B. Glucuronidation
- C. Oxidative metabolites via CYP2E1
- D. Methylation
Correct answer: C. Oxidative metabolites via CYP2E1
15. Which drug metabolizing enzyme exhibits genetic polymorphism?
- A. CYP3A4
- B. CYP2D6
- C. UGT1A1
- D. MAO-A
Correct answer: B. CYP2D6
16. The term “poor metabolizer” refers to:
- A. High clearance of drug
- B. Inability to form water-soluble metabolites
- C. Genetically reduced or absent enzyme activity
- D. Increased Phase I reactions
Correct answer: C. Genetically reduced or absent enzyme activity
17. An inhibitor of CYP enzymes can cause:
- A. Faster metabolism
- B. Drug inactivation
- C. Increased drug concentration and toxicity
- D. Improved therapeutic index
Correct answer: C. Increased drug concentration and toxicity
18. Which phase of biotransformation increases drug polarity most significantly?
- A. Phase I
- B. Phase II
- C. Both equally
- D. Neither
Correct answer: B. Phase II
19. Which dietary substance is known to inhibit CYP3A4?
- A. Caffeine
- B. Vitamin C
- C. Grapefruit juice
- D. Ginseng
Correct answer: C. Grapefruit juice
20. What is the fate of most drugs after metabolism?
- A. Stored in bone
- B. Excreted in bile
- C. Excreted in urine or bile
- D. Remain unchanged in plasma
Correct answer: C. Excreted in urine or bile
21. Which conjugation reaction involves the addition of an acetyl group?
- A. Sulfation
- B. Glucuronidation
- C. Acetylation
- D. Methylation
Correct answer: C. Acetylation
22. The methylation of catecholamines is catalyzed by:
- A. MAO
- B. COMT
- C. CYP1A2
- D. SULT
Correct answer: B. COMT
23. Which type of drug is less likely to undergo extensive biotransformation?
- A. Hydrophilic drug
- B. Lipophilic drug
- C. Weak base
- D. Prodrug
Correct answer: A. Hydrophilic drug
24. Induction of CYP enzymes typically leads to:
- A. Prolonged half-life
- B. Reduced drug clearance
- C. Faster drug metabolism
- D. Decreased enzyme activity
Correct answer: C. Faster drug metabolism
25. Rifampin is a known inducer of:
- A. CYP2D6
- B. CYP1A2
- C. CYP3A4
- D. CYP2C9
Correct answer: C. CYP3A4
26. What is glucuronide conjugation typically associated with?
- A. Drug activation
- B. Formation of active metabolites
- C. Drug inactivation and detoxification
- D. Protein binding
Correct answer: C. Drug inactivation and detoxification
27. The biotransformation pathway for isoniazid involves:
- A. Methylation
- B. Hydroxylation
- C. Acetylation
- D. Oxidation
Correct answer: C. Acetylation
28. Which enzyme system is involved in alcohol metabolism?
- A. CYP3A4
- B. ADH and ALDH
- C. UGT
- D. MAO
Correct answer: B. ADH and ALDH
29. Which phase I reaction can create reactive intermediates?
- A. Oxidation
- B. Methylation
- C. Glucuronidation
- D. Acetylation
Correct answer: A. Oxidation
30. What does ‘microsomal enzyme’ refer to in drug metabolism?
- A. Mitochondrial enzymes
- B. Cytoplasmic kinases
- C. Enzymes in the smooth endoplasmic reticulum
- D. Ribosomal enzymes
Correct answer: C. Enzymes in the smooth endoplasmic reticulum
31. Which phase II reaction is most likely to be saturable at therapeutic doses?
- A. Glucuronidation
- B. Sulfation
- C. Acetylation
- D. Methylation
Correct answer: B. Sulfation
32. Polymorphism in which enzyme is important for warfarin metabolism?
- A. CYP2D6
- B. CYP2C9
- C. CYP3A4
- D. MAO-A
Correct answer: B. CYP2C9
33. What is the purpose of hepatic portal circulation in drug metabolism?
- A. Increase systemic exposure
- B. Delay onset of action
- C. Allow liver to metabolize substances before systemic circulation
- D. Enable lymphatic absorption
Correct answer: C. Allow liver to metabolize substances before systemic circulation
34. Which of the following is NOT a Phase I metabolic reaction?
- A. Oxidation
- B. Reduction
- C. Hydrolysis
- D. Sulfation
Correct answer: D. Sulfation
35. The ‘enterohepatic circulation’ of drugs refers to:
- A. Pulmonary recirculation
- B. Biliary excretion followed by intestinal reabsorption
- C. Lymphatic transport
- D. Renal reabsorption
Correct answer: B. Biliary excretion followed by intestinal reabsorption
36. Genetic polymorphism in UGT1A1 affects which drug?
- A. Irinotecan
- B. Digoxin
- C. Metoprolol
- D. Aspirin
Correct answer: A. Irinotecan
37. What is the effect of enzyme induction on plasma concentration of a drug?
- A. Increases plasma levels
- B. No effect
- C. Decreases plasma levels
- D. Random effects
Correct answer: C. Decreases plasma levels
38. Neonates are more sensitive to some drugs due to:
- A. Excess drug excretion
- B. Enhanced metabolism
- C. Immature liver enzymes
- D. Higher gastric pH
Correct answer: C. Immature liver enzymes
39. A drug that is extensively metabolized is likely to have:
- A. High oral bioavailability
- B. Low hepatic extraction
- C. High first-pass metabolism
- D. Long half-life
Correct answer: C. High first-pass metabolism
40. Which reaction is catalyzed by monoamine oxidase (MAO)?
- A. Hydrolysis of peptides
- B. Oxidative deamination of neurotransmitters
- C. Demethylation of DNA
- D. Acetylation of amines
Correct answer: B. Oxidative deamination of neurotransmitters
41. What type of drugs are most likely to require metabolic activation?
- A. Antacids
- B. Prodrugs
- C. Antihistamines
- D. Analgesics
Correct answer: B. Prodrugs
42. Enzyme inhibition can lead to:
- A. Shorter half-life
- B. Increased clearance
- C. Higher plasma drug levels
- D. Reduced absorption
Correct answer: C. Higher plasma drug levels
43. The enzyme COMT acts on:
- A. Catecholamines
- B. Esters
- C. Peptides
- D. Lipids
Correct answer: A. Catecholamines
44. What enzyme deficiency is linked to Gilbert’s syndrome?
- A. CYP2D6
- B. CYP3A4
- C. UGT1A1
- D. COMT
Correct answer: C. UGT1A1
45. What metabolic reaction involves adding a methyl group?
- A. Acetylation
- B. Hydroxylation
- C. Methylation
- D. Sulfation
Correct answer: C. Methylation
46. Codeine is converted to morphine by:
- A. CYP3A4
- B. CYP1A2
- C. CYP2D6
- D. CYP2C19
Correct answer: C. CYP2D6
47. Which enzyme is involved in aspirin hydrolysis?
- A. CYP3A4
- B. Esterase
- C. UGT
- D. SULT
Correct answer: B. Esterase
48. What is the result of decreased biotransformation?
- A. Enhanced drug clearance
- B. Decreased therapeutic effects
- C. Drug accumulation and toxicity
- D. Rapid onset of action
Correct answer: C. Drug accumulation and toxicity
49. Why are Phase II metabolites often inactive?
- A. Highly hydrophilic and can’t bind receptors
- B. Rapidly absorbed
- C. Target mitochondria
- D. Have increased potency
Correct answer: A. Highly hydrophilic and can’t bind receptors
50. Which class of enzymes catalyzes oxidation-reduction reactions in Phase I?
- A. Esterases
- B. Transferases
- C. Cytochrome P450 enzymes
- D. Ligases
Correct answer: C. Cytochrome P450 enzymes