INTERACTIONS OF GRAPEFRUIT WITH MEDICATIONS

How common is grapefruit juice-drug interactions in clinical practice?

The potential for this type of drug interaction is enormous. Dr. David Bailey, stated in the September 3rd, 1998 issue of the Medical Tribune: 

"Sixty percent of drugs that are (commonly) prescribed are metabolized to some extent by this enzyme, CYP3A4 (Cytochrome P450 3A4). Many drugs undergo first-pass metabolism by CYP3A4. Hence, the inhibition of this enzyme in the gut causes plasma concentrations of these drugs to increase markedly after oral administration. The result can be significant. For example, taking one tablet of lovastatin (Mevacor) with a glass of grapefruit juice is the same as taking 12 to 15 tablets with a glass of water. Certain antihistamines, benzodiazepines, cyclosporin, caffeine, calcium antagonists and cisapride are among other drugs with which grapefruit interacts. So this interaction is very important and the list (of drugs) is going to continue to grow".

The list of specific drugs and drug types which interact with grapefruit juice is slowly expanding, but still very incomplete. We will take a look at few of these where clinical data is available.

Next Topic: Interaction of Grapefruit Juice with Antihistamines