2013-01-23-Grapefruit-not-only-food-that-may-affect-medication_ST_U.xml
^$^Many people have seen prescription warning labels saying "Do not eat grapefruit or drink grapefruit juice while taking this medication." But other foods can interfere with medications, too.
Milk and other calcium products, for example, can block absorption of some antibiotics. Eating lots of chocolate with some antidepressants can cause a sharp rise in blood pressure. Black licorice can reduce effects of blood pressure drugs and diuretics.
It has been known for some time that grapefruit juice can "both increase or decrease the absorption of a small number of drugs," says Hartmut Derendorf, chairman of pharmaceutics at the University of Florida College of Pharmacy. But a review in the Canadian Medical Association Journal found many new drug formulations are being added to the list.
"If the drug is metabolized in the gut wall to a large extent and this metabolism is blocked, then concentrations in the blood will go up. An example is the lipid-lowering drug simvastatin (Zocor)," Derendorf says. "For other drugs, such as the antihistamine fexofenadine (Allegra), grapefruit juice blocks the uptake into the bloodstream, and the concentrations in blood will go down."
He says alternatives are available that will not interact with grapefruit and other citrus fruits containing furanocoumarins, the culprit behind the "grapefruit juice effect." These include Seville oranges (used in marmalade), limes and tangelos, a cross between tangerines and grapefruit. Sweet oranges (navel, Valencia) contain no furanocoumarins.
There's more attention than ever being paid to reducing interactions, Derendorf says; researchers are seeking safe alternatives, removing chemicals that cause interactions and, in some cases, changing the genetic makeup of foods to stop interactions.
In December, a team at the University of Florida's Citrus Research and Education Center published a paper about efforts to create a grapefruit hybrid with significantly reduced interaction risk.
Vitamins, minerals and herbs also can interfere with some drugs.
Calcium supplements, for example, may decrease absorption of dietary iron, which is why people at high risk for iron deficiency are encouraged to take calcium at bedtime instead of with meals.
It's important to tell your physician about all the medications you're taking (prescription, over-the-counter and supplements), read packaging materials and ask about potential interactions, says Christine Gerbstadt, a registered dietitian and spokeswoman for the Academy of Nutrition and Dietetics.
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