Herbalism Herb-Drug Interactions 1 — Questions and Answers
Question 1: St. John's Wort is well documented to reduce blood levels of many pharmaceutical drugs primarily because it:
- Inhibits CYP3A4 enzymes
- Induces CYP3A4 and P-glycoprotein expression (Correct answer)
- Blocks drug absorption in the gut
- Increases renal excretion of all drugs
Correct answer: Induces CYP3A4 and P-glycoprotein expression
St. John's Wort is a potent inducer of cytochrome P450 3A4 and P-glycoprotein, causing accelerated metabolism and reduced plasma levels of many drugs.
Question 2: Which common herbal anticoagulant interaction poses the greatest risk when combined with warfarin?
- Chamomile
- Ginger and garlic increasing bleeding risk (Correct answer)
- Valerian causing sedation
- Licorice causing fluid retention
Correct answer: Ginger and garlic increasing bleeding risk
Ginger and garlic have antiplatelet properties that can potentiate warfarin's anticoagulant effect, increasing the risk of bleeding.
Question 3: Patients taking MAO inhibitors (MAOIs) should avoid which herbal supplement due to the risk of hypertensive crisis?
- Lavender
- Ginkgo biloba
- Kava kava
- Tyramine-rich herbal tonics and fermented preparations (Correct answer)
Correct answer: Tyramine-rich herbal tonics and fermented preparations
Tyramine-containing herbs and foods can trigger a dangerous hypertensive crisis in patients taking MAOIs because MAOIs prevent tyramine breakdown.
Question 4: Which herb is most likely to interfere with immunosuppressant drugs like cyclosporine following organ transplant?
- Peppermint
- St. John's Wort (Correct answer)
- Slippery elm
- Marshmallow root
Correct answer: St. John's Wort
St. John's Wort induces liver enzymes that rapidly metabolize cyclosporine, potentially leading to organ rejection by dropping drug levels too low.
Question 5: Kava kava combined with central nervous system depressants such as benzodiazepines may cause:
- Increased drug clearance
- Additive CNS depression and sedation (Correct answer)
- Reduced effectiveness of the benzodiazepine
- Mild stimulatory effects
Correct answer: Additive CNS depression and sedation
Kava's kavalactones exert GABA-A receptor activity, adding to the CNS depressant effects of benzodiazepines and increasing sedation risk.
Question 6: Licorice root (Glycyrrhiza glabra) can potentiate the effects of corticosteroids primarily because glycyrrhizin:
- Directly mimics cortisol in the body
- Inhibits the enzyme 11β-HSD that breaks down cortisol (Correct answer)
- Increases adrenal gland size
- Stimulates the pituitary to release ACTH
Correct answer: Inhibits the enzyme 11β-HSD that breaks down cortisol
Glycyrrhizin inhibits 11β-hydroxysteroid dehydrogenase, which normally deactivates cortisol, leading to elevated cortisol and potentiation of steroid drugs.
Herbalism Herb-Drug Interactions 1
St.
John's Wort is well documented to reduce blood levels of many pharmaceutical drugs primarily because it: