How can grapefruit juice affect drug levels, and which drug classes are most affected?

• A. It reduces drug levels by inducing metabolism.
• B. It has no effect on drug levels.
• C. It inhibits intestinal CYP3A4, increasing levels of certain statins, calcium channel blockers, macrolide antibiotics, and immunosuppressants.
• D. It only affects antibiotics.

Answer: (C)