Enzyme grapefruit juice, effect

In addition to the problem of immediate potential toxicity of plant chemicals, there is a growing body of evidence that points to adverse interactions between foods and pharmaceuticals. For example, bergamottin in grapefruit juice is responsible for the grapefruit juice effect on the bioavailability of several prescription drugs. The compound inhibits cytochrome P-450 enzymes responsible for drug metabolism... 

Some chemical exposures may be hepatic enzyme inducers/inhibitors, altering the effects of drugs like warfarin. Some foods such as mono-amines, will cause reactions in patients given MAOIs grapefruit juice may interact with terfenadine and some other drugs. New diseases may cause problems heart failure causing reduced liver blood flow can reduce the metabolism of drugs like warfarin. 

Tobacco and rifampin both induce hepatic enzymes, which may decrease the duration of action of the BZs. Grapefruit juice has received recent recognition as a factor in the pharmacokinetics of many drugs. Grapefruit juice slows down the GI absorption of midazolam and also decreases biotransformation, which leads to a delayed onset of effect and an increase in drowsiness (Ameer and Weintraub, 1997). 

Table V. Effect of Enzyme Treatment on Naringin Content and Bit-terness Perception in Grapefruit Juice.(79) ...

Grapefruit juice also inhibits the CYP1A2 enzyme system in vitro but not in vivo. This is consistent with the understanding that the effect of grapefruit juice occurs at the level of the intestinal wall where levels of CYP2A expression are low. These CYP2A substrates studied with grapefruit juice have included caffeine, theophylline, and coumarin (Table 34.1). 

One area that has received a considerable amount of recent attention is the inhibition of intestinal CYP enzymes by components of grapefruit juice.48 This effect has been shown to produce substantial increases in the plasma concentrations of a wide variety of CYP3A substrates. 

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