Answer to Question 1
Some food components alter the activities of enzymes that metabolize drugs or may counteract drug effects in other ways. Compounds in grapefruit juice (or whole grapefruit) have been found to inhibit or inactivate enzymes that metabolize a number of different drugs. As a result of the reduced enzyme action, blood concentrations of the drugs increase, leading to stronger physiological effects. The effect of grapefruit juice can last for a substantial period, possibly as long as several days after the juice is consumed; thus, the interaction cannot be avoided just by separating grapefruit juice consumption from drug administration.
Answer to Question 2
B