- No caffeine-containing food or beverages (e.g., coffee, colas, chocolate, or over-the-counter medications) or food items that have been reported to affect drug/carcinogen metabolizing enzymes (e.g., grapefruit, grapefruit juice, cruciferous vegetables, and food cooked over charcoal) beginning 72 hours before and until 8 hours after each set of CYP probe drug administration