Adverse Drug Reactions and Interactions · USMLE Step 1

Grapefruit juice can increase plasma levels of certain medications by inhibiting which enzyme in the gut and liver?

  1. CYP1A1
  2. CYP3A4
  3. MAO-A
  4. CYP2D6
Show answer and explanation

Correct answer: CYP3A4

Grapefruit juice contains furanocoumarins that irreversibly inhibit CYP3A4 in intestinal and hepatic cells, reducing first-pass metabolism and increasing drug concentrations.

Difficulty: Medium Question 5 of 19

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