The Grapefruit Juice Effect

A drug interaction is the effect that a substance can have when taken together with a drug. Grapefruit juice has proven to be a source of interaction with many drugs, causing increased bioavailability, leading to possible toxicity and increased instances of side effects. This paper discusses the mechanisms of the interaction and the components of grapefruit juice responsible for the interaction, as well as two classes of drugs that are affected, calcium channel antagonists and HMGCoA reductase inhibitors, and possible ways to avoid the interaction. The mechanisms are inhibition of the enzyme cytochrome P-450 3A4 (CYP3A4) and the transport molecule P-glycoprotein. Furancoumarins are responsible for the interaction. In general, drugs that are affected have a low oral bioavailability and are substrates of CYP3A4. The interaction is best avoided by not drinking grapefruit juice, or choosing a drug that doesn’t interact. Other possibilities include juice low in furanocoumarins due to harvest factors, and furanocoumarin free juice. In conclusion, one should exercise caution unless it has been proven that the drugs being taken do not interact with grapefruit juice