Question

Drug interaction with grapefruit juice involves ________.

• A. CYP450 inhibition
• B. renal excretion
• C. increased metabolism
• D. enzyme induction

Hint:

Grapefruit juice interaction: - Mechanism: Irreversible inhibition of intestinal CYP3A4. - Outcome: Increases the bioavailability and toxicity risk of drugs like statins and calcium channel blockers.

Answer 1

The Correct Option is A

Concept: Grapefruit juice contains bio-active organic compounds, including furanocoumarins (such as bergamottin and dihydroxybergamottin) and flavonoids (such as naringin). These compounds act as potent, mechanism-based (irreversible) inhibitors of the CYP3A4 enzyme, a major member of the Cytochrome P450 enzyme family located in the intestinal wall and liver.

Step 1: Determine the mechanism of interaction.
When a patient consumes grapefruit juice along with drugs metabolized by CYP3A4 (such as simvastatin, amlodipine, or cyclosporine), the inhibition of intestinal CYP3A4 prevents presystemic first-pass metabolism. This leads to significantly increased bio-availability and elevated plasma concentrations of the drug, which can cause toxicity. Thus, the correct option is CYP450 inhibition.