Grapefruit not so great with some medications
Grapefruit has always been viewed as a healthful food. It has been touted as a weight loss miracle and an excellent source of vitamin C and potassium. But before washing down certain medications with a glass of grapefruit juice, one should be aware that the interaction of the fruit with the drug may cause adverse effects. According to the Food and Drug Administration, grapefruit interferes with the actions of both prescription and over-the-counter drugs.
The effect of grapefruit depends on the type of medication consumed, as it can either increase levels of absorption of the medication into the body or limit its effectiveness.
Recent FDA reports of drugs that interact with grapefruit include cholesterol medications such as Lipitor, anti-depressant medications such as Zoloft, and antihistamine medications such as Allegra.
According to The Harvard Medical School Family Health Guide, certain benzodiazepines—or anti-anxiety medications—such as Valium also interact with the fruit, as do some calcium channel blockers used to treat high blood pressure.
Grapefruit has the potential to affect the body even if the fruit or juice has been consumed days before or after the medications, according to the American Academy of Family Physicians.
The National Center for Biotechnology Information reports that in the body, grapefruit blocks CYP3A4, an enzyme involved in drug metabolism that helps break down substances in the small intestine.
When this enzyme is blocked, the absorption of certain drugs into the bloodstream is increased, which can ultimately lead to dangerously high drug concentrations and increased overdose risk, the FDA reports.
Santa Monica College nursing professor and registered nurse Dr. Vini Angel claims that there are vital concerns regarding the effects of grapefruit in the body, especially for organ transplant recipients.
“[For] an organ transplant recipient taking cyclosporine to prevent organ rejection, grapefruit and grapefruit juice must be avoided because it increases absorption, which increases the risk of drug toxicity,” says Angel.
Doctors are not certain which chemical compound in grapefruit is responsible for interacting with medications, but many believe that it may be a component called furanocoumarin, according to a report from Harvard Medical School. Tangelos and Seville oranges, commonly used to make orange marmalade, also contain furanocoumarin.
The report states that not much grapefruit is needed to cause a reaction in the body. A single glass of grapefruit juice can produce a 47 percent reduction of the intestinal enzyme that regulates absorption, which can increase overdose risk.
With other medications, grapefruit may have the exact opposite effect by blocking the transporter proteins necessary for absorption, thus lowering the amount absorbed. The FDA reports that grapefruit blocks transporters in anti-allergy medications such as Allegra, which can reduce effectiveness.
Not all medications are affected by grapefruit, so the FDA recommends consulting with a local pharmacist or healthcare provider to find out whether a prescription is contraindicated.
“Registered nurses also teach patients about drug-food interactions and which foods they should avoid,” says Angel.