Enzyme induction MCQs With Answer

Enzyme induction MCQs With Answer is a focused set of practice questions designed for B. Pharm students to deepen understanding of drug metabolism, pharmacokinetics, and clinical drug interactions. This introduction covers mechanisms of enzyme induction, key inducers (rifampicin, carbamazepine, phenobarbital, St. John’s wort, smoking), nuclear receptors (PXR, CAR), affected enzymes (CYP3A4, CYP2C9, CYP1A2, UGT), clinical consequences (reduced drug efficacy, contraceptive failure, altered prodrug activation), and timelines for onset and resolution. These MCQs emphasize application, interpretation of interaction outcomes, and monitoring strategies essential for safe pharmacotherapy. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the primary molecular mechanism by which rifampicin induces hepatic drug-metabolizing enzymes?

• Competitive inhibition of CYP450 enzymes
• Activation of nuclear receptors (e.g., PXR) increasing gene transcription
• Direct phosphorylation of enzyme proteins enhancing activity
• Increasing hepatic blood flow to clear drugs faster

Correct Answer: Activation of nuclear receptors (e.g., PXR) increasing gene transcription

Q2. Which cytochrome P450 isoform is most commonly induced by many clinically important inducers like rifampicin and phenobarbital?

• CYP2D6
• CYP3A4
• CYP2E1
• CYP2C19

Correct Answer: CYP3A4

Q3. Which statement correctly distinguishes enzyme induction from enzyme inhibition?

• Induction decreases enzyme protein levels; inhibition increases levels
• Induction is rapid (minutes); inhibition takes days to develop
• Induction increases synthesis of enzymes; inhibition reduces enzyme activity
• Induction always causes toxicity; inhibition never does

Correct Answer: Induction increases synthesis of enzymes; inhibition reduces enzyme activity

Q4. Autoinduction refers to which phenomenon?

• A drug reducing its own absorption in the gut
• A drug inducing the metabolic enzymes that accelerate its own clearance
• A drug inhibiting the enzymes that metabolize other drugs
• A drug causing immune-mediated clearance of itself

Correct Answer: A drug inducing the metabolic enzymes that accelerate its own clearance

Q5. Which of the following drugs is a classic example of an autoinducing anticonvulsant?

• Valproic acid
• Carbamazepine
• Levetiracetam
• Benzocaine

Correct Answer: Carbamazepine

Q6. St. John’s wort can reduce plasma concentrations of oral contraceptives primarily because it:

• Inhibits CYP2D6, decreasing hormone clearance
• Induces CYP3A4, increasing metabolism of contraceptive hormones
• Blocks intestinal absorption of hormones by binding them
• Competes with estrogen for receptor binding

Correct Answer: Induces CYP3A4, increasing metabolism of contraceptive hormones

Q7. Which nuclear receptor is most closely associated with induction of CYP3A4?

• Glucocorticoid receptor (GR)
• PXR (Pregnane X Receptor)
• Estrogen receptor (ER)
• Vitamin D receptor (VDR)

Correct Answer: PXR (Pregnane X Receptor)

Q8. The clinical consequence of enzyme induction on warfarin is usually:

• Increased INR and bleeding risk
• Decreased warfarin clearance and toxicity
• Decreased INR due to increased warfarin metabolism
• No change in anticoagulant effect

Correct Answer: Decreased INR due to increased warfarin metabolism

Q9. Which inducer is strongly associated with increased metabolism of theophylline and caffeine via CYP1A2 induction?

• Rifampicin
• Smoking (polycyclic aromatic hydrocarbons)
• Fluoxetine
• Allopurinol

Correct Answer: Smoking (polycyclic aromatic hydrocarbons)

Q10. Time course of enzyme induction after starting an inducer is typically:

• Within minutes
• Hours to days
• Days to weeks
• Months to years

Correct Answer: Days to weeks

Q11. Induction of phase II enzymes (e.g., UGTs) will most likely result in:

• Reduced conjugation and drug accumulation
• Increased conjugation and enhanced drug clearance
• Direct inhibition of transporter proteins
• Selective inhibition of CYP enzymes only

Correct Answer: Increased conjugation and enhanced drug clearance

Q12. Which laboratory finding suggests in vivo enzyme induction of a drug metabolized by a specific pathway?

• Increased plasma concentration of parent drug with reduced metabolites
• Decreased clearance and longer half-life
• Decreased plasma concentration of parent drug and increased metabolite ratio
• No change in pharmacokinetic parameters

Correct Answer: Decreased plasma concentration of parent drug and increased metabolite ratio

Q13. Which drug interaction is most likely when rifampicin is co-administered with oral midazolam?

• Rifampicin inhibits midazolam causing sedation
• Rifampicin induces midazolam metabolism reducing its sedative effect
• Rifampicin and midazolam compete for renal excretion
• Midazolam induces rifampicin metabolism

Correct Answer: Rifampicin induces midazolam metabolism reducing its sedative effect

Q14. Which statement about enzyme induction reversibility is correct?

• Enzyme levels return to baseline immediately after stopping the inducer
• Induction persists until new enzyme proteins are synthesized
• Inducers irreversibly change DNA causing permanent induction
• Induction resolves gradually over days to weeks after discontinuation

Correct Answer: Induction resolves gradually over days to weeks after discontinuation

Q15. Phenobarbital induces multiple enzymes. One clinical implication is:

• Enhanced effect of warfarin leading to bleeding
• Reduced effectiveness of oral contraceptives and some antibiotics
• Increased blood levels of psychostimulants
• Immediate allergic reactions

Correct Answer: Reduced effectiveness of oral contraceptives and some antibiotics

Q16. Which assay approach is commonly used in vitro to screen for enzyme induction potential of a new drug candidate?

• Single-dose acute toxicity test in humans
• Hepatocyte or reporter gene assays measuring CYP mRNA or activity
• Renal clearance studies in rodents
• Protein binding assays only

Correct Answer: Hepatocyte or reporter gene assays measuring CYP mRNA or activity

Q17. A prodrug that requires CYP activation may show what effect when co-administered with a strong inducer?

• Decreased activation and reduced efficacy
• Increased activation and potentially enhanced effect
• No change because induction only affects parent drugs
• Immediate allergic sensitization to the prodrug

Correct Answer: Increased activation and potentially enhanced effect

Q18. Which of the following is NOT typically considered a mechanism of enzyme induction?

• Increased gene transcription via nuclear receptors
• Enhanced mRNA stability leading to more translation
• Direct covalent activation of pre-existing enzyme protein
• Increased translation of enzyme mRNA

Correct Answer: Direct covalent activation of pre-existing enzyme protein

Q19. Co-administration of rifampicin with oral tacrolimus typically requires:

• Lowering the tacrolimus dose due to reduced clearance
• No dose change because rifampicin only affects antibiotics
• Increasing the tacrolimus dose because rifampicin induces its metabolism
• Switching to intravenous tacrolimus

Correct Answer: Increasing the tacrolimus dose because rifampicin induces its metabolism

Q20. Carbamazepine induction of its own metabolism results in which pharmacokinetic change over time?

• Progressive decrease in clearance leading to accumulation
• Progressive increase in clearance leading to lower plasma levels
• No change after the first dose
• Immediate decrease in bioavailability only

Correct Answer: Progressive increase in clearance leading to lower plasma levels

Q21. Which environmental exposure is known to induce CYP1A2 activity?

• Grapefruit juice
• Cigarette smoke
• High-fiber diet
• Cold ambient temperature

Correct Answer: Cigarette smoke

Q22. Which herbal supplement is a potent inducer of CYP3A4 and can cause multiple drug interactions?

• Ginkgo biloba
• St. John’s wort
• Echinacea
• Turmeric

Correct Answer: St. John’s wort

Q23. Induction of drug-metabolizing enzymes can affect therapeutic drug monitoring by:

• Causing misinterpretation if sampling does not account for altered clearance
• Eliminating the need for monitoring because levels become stable
• Making assays more accurate automatically
• Only affecting urine tests, not plasma

Correct Answer: Causing misinterpretation if sampling does not account for altered clearance

Q24. Which of the following drugs is an inducer known to reduce plasma concentrations of HIV protease inhibitors?

• Ketoconazole
• Rifampicin
• Itraconazole
• Cimetidine

Correct Answer: Rifampicin

Q25. Which clinical strategy is appropriate when adding a known inducer to a patient’s regimen?

• Ignore the interaction because induction is insignificant
• Monitor therapeutic effect and consider dose adjustment or alternative drug
• Immediately stop the inducer without consultation
• Switch all drugs to prodrugs

Correct Answer: Monitor therapeutic effect and consider dose adjustment or alternative drug

Q26. Which of the following best explains why induction effects may vary between patients?

• Genetic polymorphisms, concomitant drugs, age, liver function, and diet
• All patients have identical induction responses
• Induction is only determined by drug dose and nothing else
• Induction depends only on renal excretion rates

Correct Answer: Genetic polymorphisms, concomitant drugs, age, liver function, and diet

Q27. Which drug is least likely to be affected by CYP3A4 induction?

• Simvastatin
• Midazolam
• Insulin (exogenous peptide)
• Tacrolimus

Correct Answer: Insulin (exogenous peptide)

Q28. A patient on oral antibiotic therapy becomes pregnant and starts rifampicin for tuberculosis. What is a major concern regarding her contraceptive method?

• Rifampicin enhances contraceptive action increasing side effects
• Rifampicin induces metabolism of hormonal contraceptives causing failure
• Rifampicin has no interaction with hormonal contraception
• Rifampicin converts hormones to active teratogens

Correct Answer: Rifampicin induces metabolism of hormonal contraceptives causing failure

Q29. Which monitoring parameter is most useful when a patient on chronic therapy starts a potent inducer that affects a narrow therapeutic index drug?

• Clinical signs only, laboratory tests unnecessary
• Plasma drug concentration and relevant clinical effect measurements (e.g., INR for warfarin)
• Random urine color checks
• Complete blood count weekly regardless of drug

Correct Answer: Plasma drug concentration and relevant clinical effect measurements (e.g., INR for warfarin)

Q30. Which best describes the clinical importance of distinguishing between enzyme induction and enzyme inhibition?

• Both have identical clinical time courses and management strategies
• Induction often requires dose increases or alternative drugs and has delayed onset/reversal, while inhibition may cause immediate toxicity and needs prompt dose reduction
• Inhibition always leads to therapeutic failure while induction always causes toxicity
• Neither affects drug dosing decisions in clinical practice

Correct Answer: Induction often requires dose increases or alternative drugs and has delayed onset/reversal, while inhibition may cause immediate toxicity and needs prompt dose reduction

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com