More Dangerous Than You Think

Grapefruit Juice and the Potential for Drug Interactions

 

The Era of Dietary Supplements

In 2004, the FDA halted retail sales of the herbal stimulant ephedra, after its use was linked to 155 deaths (AP, 2004). Among the more serious side effects associated with ephedra were heart attacks and strokes (AP, 2004). However, for every ephedra-containing supplement banned, there are many more "miracle in a bottle" pills to take its place (Specter, 2004). The myriad of herbal and dietary supplements available to American consumers present concerns that these unregulated products present dangers to public health.

One of the more popular ephedra alternatives that has popped up in the marketplace is bitter orange. Bitter orange contains synephrine which is a chemical stimulant similar to ephedra. However, what many people do not realize about bitter orange-a sour "Seville orange"-is that it is closely related to the grapefruit (AP, 2004).

 

Figure 1: A comparison of the closely related Seville orange on the left and the grapefruit on the right

 

The Not so Innocuous Grapefruit

A Serendipitous Discovery

Grapefruit juice was once used in a drug trial for the calcium channel antagonist felodipine to mask the taste of the ethanol used to dissolve the drug (Dahan et al, 2003 ). Surprisingly, however, the results of this study were that the felodipine concentrations found in treated patients' serum were higher than ever observed in other investigations of the same drug. Eventually, the investigators pinpointed the culprit-the grapefruit juice (Dahan et al, 2003). This single factor-grapefruit juice-enhanced the bioavailability of felodipine, which has the potential to alter the pharmacokinetic and pharmacodynamic parameters of the drug seen in previous clinical trials. Current research focuses on various mechanisms of interaction between grapefruit juice and drugs as well as to identify the constituents of grapefruit juice responsible for drug interactions.

This website serves as both an introduction to the way some drugs are metabolized in the body, as well as a presentation of some of the components in grapefruit juice that may be culpable of causing surprisingly detrimental drug interactions.

 

 

Xuemei Cai · caix@email.arizona.edu

Biochemistry 462b Honors Project · The University of Arizona

Instructor Dr. Don Bourque

Last Revised May 2004