Which statement about St. John's wort and calcium channel blockers is true?

Which statement about St. John's wort and calcium channel blockers is true?

• A. Reduces effectiveness
• B. Increases effectiveness
• C. No effect
• D. Causes toxicity

Answer: (A)

This question focuses on how St. John’s wort affects calcium channel blockers through enzyme induction that changes drug levels. St. John’s wort increases the activity of liver enzymes (mainly CYP3A4) and P-glycoprotein, which speeds up the metabolism and clearance of many medications. Calcium channel blockers used for hypertension are substrates of these pathways, so when St. John’s wort is taken with them, their plasma concentrations drop. That leads to a reduced antihypertensive effect, meaning poorer blood pressure control. It’s a pharmacokinetic interaction, and it’s not associated with increased toxicity from the calcium channel blocker; rather, it can cause subtherapeutic drug levels. The statement that best fits is that St. John’s wort reduces the effectiveness of calcium channel blockers.

This question focuses on how St. John’s wort affects calcium channel blockers through enzyme induction that changes drug levels. St. John’s wort increases the activity of liver enzymes (mainly CYP3A4) and P-glycoprotein, which speeds up the metabolism and clearance of many medications. Calcium channel blockers used for hypertension are substrates of these pathways, so when St. John’s wort is taken with them, their plasma concentrations drop. That leads to a reduced antihypertensive effect, meaning poorer blood pressure control. It’s a pharmacokinetic interaction, and it’s not associated with increased toxicity from the calcium channel blocker; rather, it can cause subtherapeutic drug levels. The statement that best fits is that St. John’s wort reduces the effectiveness of calcium channel blockers.