Herb–drug and herb–food interactions: examples and management MCQs With Answer

Introduction

This MCQ set on Herb–drug and herb–food interactions: examples and management is designed for M.Pharm students preparing for Advanced Pharmacognosy I (MPG 102T). The questions emphasize clinically relevant mechanisms (CYP enzymes, transporters, platelet function, vitamin K effects), representative herb and food examples, and practical management strategies such as therapeutic drug monitoring, dose adjustment, and patient counseling. Each question tests conceptual understanding and application to real-world scenarios—helpful for exam preparation and safer patient care. Answers are provided to enable self-assessment and deeper study of interaction pathways and evidence-based interventions.

Q1. Which constituent of St John’s wort is primarily responsible for potent induction of CYP3A4 and P-glycoprotein?

• Hyperforin
• Hypericin
• Ginkgolide
• Allicin

Correct Answer: Hyperforin

Q2. Grapefruit juice can markedly increase systemic exposure of which drug by inhibiting intestinal CYP3A4 and affecting OATP-mediated uptake?

• Felodipine
• Warfarin
• Digoxin
• Metformin

Correct Answer: Felodipine

Q3. Which herbal product is well known to reduce warfarin anticoagulant effect by inducing hepatic CYP enzymes and accelerating warfarin clearance?

• St John’s wort
• Garlic
• Ginkgo biloba
• Cranberry

Correct Answer: St John’s wort

Q4. The increased bleeding risk observed when garlic supplements are taken with anticoagulants is primarily due to which mechanism?

• Inhibition of platelet aggregation
• Induction of CYP3A4 leading to higher anticoagulant levels
• High vitamin K content neutralizing anticoagulant effect
• Inhibition of P-glycoprotein decreasing drug clearance

Correct Answer: Inhibition of platelet aggregation

Q5. Regular consumption of green tea may reduce INR in patients on warfarin primarily because of which constituent-related effect?

• Inhibition of CYP2C9
• Vitamin K content
• Increased P-glycoprotein activity
• Direct anticoagulant effect

Correct Answer: Vitamin K content

Q6. Ginkgo biloba increases bleeding risk when combined with antiplatelet or anticoagulant drugs mainly by which pharmacologic action?

• Inhibition of platelet-activating factor
• Induction of CYP3A4 metabolism
• Inhibition of vitamin K epoxide reductase
• Activation of warfarin metabolism via CYP2C9

Correct Answer: Inhibition of platelet-activating factor

Q7. A patient on chronic benzodiazepine therapy asks about starting kava for anxiety. What is the most appropriate recommendation?

• Avoid coadministration due to additive CNS depression and hepatotoxicity
• No precautions are required—kava is safe with benzodiazepines
• Increase the benzodiazepine dose to compensate for interaction
• Take kava only in the morning to reduce interaction risk

Correct Answer: Avoid coadministration due to additive CNS depression and hepatotoxicity

Q8. Curcumin (from turmeric) can potentiate warfarin anticoagulation by inhibiting which cytochrome P450 isoform primarily responsible for S‑warfarin metabolism?

• CYP3A4
• CYP1A2
• CYP2C9
• P-glycoprotein

Correct Answer: CYP2C9

Q9. Grapefruit juice can alter oral drug absorption by inhibiting which intestinal uptake transporter?

• P-glycoprotein (P-gp)
• OATP1A2
• OCT1
• BCRP (ABCG2)

Correct Answer: OATP1A2

Q10. To minimize interaction between tea (tannins) and an oral iron supplement, what minimum spacing is commonly recommended?

• 30 minutes
• 2 hours
• 12 hours
• No need to separate; take together

Correct Answer: 2 hours

Q11. A transplant patient on cyclosporine wishes to take St John’s wort. Which is the safest management step?

• Temporarily double the cyclosporine dose without monitoring
• Avoid concomitant use and monitor cyclosporine levels if exposure occurred
• No change required—St John’s wort is safe with cyclosporine
• Switch cyclosporine to a statin to avoid interaction

Correct Answer: Avoid concomitant use and monitor cyclosporine levels if exposure occurred

Q12. Which herbal supplement is most strongly associated with precipitating serotonin syndrome when combined with SSRIs?

• St John’s wort
• Ginkgo biloba
• Garlic
• Echinacea

Correct Answer: St John’s wort

Q13. Which food is most likely to antagonize warfarin therapy due to high vitamin K content?

• Grapefruit
• Spinach
• Cranberry juice
• Ginger

Correct Answer: Spinach

Q14. Chronic use of St John’s wort can lower plasma concentrations of digoxin primarily by induction of which efflux transporter?

• St John’s wort
• Grapefruit juice
• Aloe vera
• Licorice

Correct Answer: St John’s wort

Q15. If a clinically important herb–drug interaction is unavoidable and there is no alternative therapy, the best general management strategy is which of the following?

• Stop the prescribed drug and substitute the herb
• Ignore the interaction since effects are usually minor
• Therapeutic drug monitoring and dose adjustment with close clinical monitoring
• Double the dose of the interacting drug to overcome the effect

Correct Answer: Therapeutic drug monitoring and dose adjustment with close clinical monitoring

Q16. Which herbal product has a recognized risk of hepatotoxicity and should be used cautiously or avoided with other hepatotoxic drugs?

• Kava
• Ginkgo biloba
• Ginger
• Echinacea

Correct Answer: Kava

Q17. Which grapefruit constituent is chiefly implicated in irreversible inhibition of intestinal CYP3A4 leading to clinically significant interactions?

• Bergamottin (a furanocoumarin)
• Hyperforin
• Berberine
• Allicin

Correct Answer: Bergamottin (a furanocoumarin)

Q18. Which herb is known to potentiate the effect of oral hypoglycemic drugs and may increase risk of hypoglycemia?

• Fenugreek
• Ginkgo biloba
• St John’s wort
• Aloe vera

Correct Answer: Fenugreek

Q19. Which herbal product is reported to inhibit CYP3A4 and thereby can increase plasma levels of CYP3A4‑metabolized statins?

• Goldenseal
• St John’s wort
• Garlic
• Echinacea

Correct Answer: Goldenseal

Q20. A patient on warfarin plans to start an over-the-counter herbal supplement. What is the most appropriate immediate advice?

• Stop warfarin and take the herbal supplement instead
• Continue warfarin as usual; herbs do not affect INR
• Obtain baseline INR, consult the prescriber, and arrange close INR monitoring after starting the supplement
• Only use herbal teas labeled “safe with warfarin” without consulting a clinician

Correct Answer: Obtain baseline INR, consult the prescriber, and arrange close INR monitoring after starting the supplement

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