The University Record, June 11, 1997

Grapefruit 'juices' up certain drugs

By Pete Barkey
Medical Center Public Relations

If you want your medicine to work harder, you might want to pay closer attention to your breakfast menu. In a follow-up to an earlier study, a Medical Center physician and his colleagues have expanded research into how and why grapefruit juice helps the body absorb some medications more efficiently.

Paul B. Watkins, director of the General Clinical Research Center, earlier found that patients who took certain medications with grapefruit juice absorbed more of the medicine.

The key to how grapefruit juice enhances drug absorption, according to Watkins, lies in the interaction between the grapefruit juice and an enzyme found in the small intestine. The new study found that the juice actually decreases the amount of this enzyme, which normally acts as a sort of medicinal gatekeeper. People typically have varying amounts of the enzyme in their intestines, possibly explaining why some absorb greater amounts than others.

Watkins and his colleagues feel this new study, published in the May 15 Journal of Clinical Investigation, opens the door to greater control over how much medication is delivered from a given dose. Researchers now believe that by adding the responsible substance contained in grapefruit directly into oral medications, the reliability and safety of certain drugs can be noticeably improved. Additionally, a better understanding of the link between grapefruit juice and drug absorption has far-reaching ramifications into the role that diet plays in how efficiently the body absorbs medication.