Fruit Juices and your medicines: not a good combination

Twenty years ago, Dr David Bailey and colleagues in the University of Western Ontario, Canada, were the first to note the unholy combination of grapefruit juice and medicines by increasing the level of the drug in the body making it more toxic and more side effects. Now, Dr Bailey gives new evidence that grapefruits, as well as oranges and apples, can also give the opposite effect – that is, reducing a drug’s effects by preventing its absorption in the intestines. The drug that he currently studied was the antihistamine fexofenadine though other drugs like the beta-blocker, atenolol, antibiotics such as ciprofloxacin and levofloxacin, and many others are also thought to be influenced by the presence of such fruits. The culprit in the grapefruit is a flavonoid called naringin, and it is known to be highly particular for water-soluble and highly polarized drugs and vitamins.

Dr Bailey and colleagues first reported this “Grapefruit juice effect” when they observed that combining grapefruit and the antihypertensive felodipine boosted the drug’s blood level. Since then, other studies have included nearly 50 drugs more that can be acted upon by this seemingly innocent fruit.

His advice to all: drink your medicine on an empty stomach unless it is needed or recommended to take them with food.