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
