INTERACTIONS OF GRAPEFRUIT WITH MEDICATIONS

In The Beginning..The Genesis of the Grapefruit Interaction

The grapefruit juice interaction originates from its connection to an enzyme called cytochrome P450, an enzyme that plays a pivotal role in the way a medication gets absorbed to our body after we consume it.

A Short Description of the Technical Jargon

When we take a medicine orally (by mouth), it has to get into our blood stream to do its job. (The medications that are intravenously administered, sidesteps this process and gets directly into the blood stream. That is why many of the medications that can be administered orally and intravenously, can be safely used in the intravenous route, while the oral route are subject to interactions.) The absorption usually takes place in the large or small intestines. The liver plays a key role in many of these metabolism b y removing a significant amount of the medication from the serum. For many medications, there is an optimum concentration of the active ingredient that need to be present in the serum for a certain amount of time for it to work. So, two factors are important. The maximum concentration of the active ingredient in the serum (called Cmax). The time factor is determined by plotting the concentration in the blood stream versus time and determining the area under the curve (AUC). Obviously, more AUC means we had been exposed to this ingredient for a longer time. Any mechanism that alters the optimum values of Cmax and AUC can affect the way the drug reacts. We will see later that grapefruit affects both Cmac and AUC for several prescription medications that take advantage of the Cytochrome P450 isoenzyme for the metabolism of the drug.

All drugs and many other substances within our body such as prostaglandins, fatty acids and steroids, utilize one or more of the cytochrome P450 isoenzymes in their respective metabolic (elimination) pathways. It turns out that one of the most important dietary factors that affects this isoenzyme is a bioflavinoid and possibly other ingredients contained in grapefruits and in grapefruit juice.

Next Topic: How Does Grapefruit Cause Such Interaction with Medications?