Harvard Health Letter

By the way, doctor: Does grapefruit juice affect aspirin?

Q. I am 78, and for about 10 years, I have been taking an 81-mg aspirin every morning with a glass of grapefruit juice. I heard that it's not a good idea to drink grapefruit juice with some blood-thinning drugs. Is that true of aspirin too?

A. Like you and millions of other people, I love the taste of grapefruit juice. It also has many health-promoting substances in it. However, around 1987 it was accidentally discovered that grapefruit juice can change the blood levels of many drugs, raising several of them and lowering a few others. As you might imagine, these changes can cause side effects or reduce a drug's effectiveness. Whether a drug is affected by grapefruit juice depends on how it's metabolized in the liver.

Although most medications aren't affected, some of the most commonly prescribed ones are. These include several of the cholesterol-lowering statin drugs, several calcium-channel blockers, the blood pressure drug losartan (Cozaar), several sedatives and sleeping pills, and drugs for erectile dysfunction, such as sildenafil (Viagra). To make things more complicated, the effects of grapefruit juice on the levels of a particular drug can be quite variable from one person to the next.

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