Grapefruit Juice Increases Drug Potency

A recent article from the New York Times (free subscription required for viewing), detailed how grapefruit juice can increase the potency of some drugs to potentially dangerous levels through its inhibition of certain enzymes.

A group of enzymes called the cytochrome P 450 system, specifically an enzyme called CYP 3A4, held the answer as to why grapefruit juice increased the power of certain drugs so greatly. These enzymes break down many drugs and toxins into substances that are "less potent or more easily excreted or both," according to the article. Grapefruit juice inhibits the ability of CYP 3A4 to break down these drugs, increasing its potency because more can enter the bloodstream. The drug specifically binds with the enzyme in the intestines, so this effect can only happen if the drug is taken orally.

The vast majority of grapefruit juice’s interactions with drugs are not very serious, though some special cases do arise. Cholesterol lowering drugs like Lipitor and Zocor have increased potency, which can lead to a fatal muscle disorder. Grapefruit juice can also hinder the metabolism of drugs like Prozac, used to treat depression. Grapefruit juice has the greatest effect, but lime juice and orange juice made from Seville oranges affect the enzyme in similar ways.

Solution: take the drugs with water.