Recently I was asked why grapefruit can interfere with some medications – the answer to which doctors have suspected for many years, but has only been known definitively since 1989. The simplest answer is that grapefruit can block our digestive enzymes from breaking down medications, which makes those medications stronger than prescribed. Prescription overdose is a risk when grapefruit (or grapefruit juice) is present – even in small amounts and even if eaten up to three days before starting the medication.
It’s important to look for any grapefruit related warning labels on prescription medication specifically because no single class of drugs is affected. Drugs that interact with grapefruit are typically taken orally, metabolized by the CYP3A4 Enzyme and found in very small amounts in the part of the circulatory system that moves oxygen from the heart to the rest of the body. This is especially important for those on high blood pressure medications. Some of the most common drugs affected by grapefruit are Lipitor, Zocor, Procardia and cyclosporine drugs.
Allegra, and several others drugs used to treat allergies, can be blocked by grapefruit , causing the opposite affect and decreasing its effectiveness. To date, the FDA lists over 85 drugs that can be adversely affected by grapefruit.
Grapefruit isn’t the only fruit to be cautions with when taking prescription medication. Some studies have shown that apple juice can be dangerous as well, decreasing the body’s ability to absorb antibiotics, antihistamines, certain chemo drugs and beta blockers. Pomegranate juice may also cause similar problems to those of grapefruit. Always discuss with your pharmacist any interactions listed for your particular prescription medication.