A leading expert explains how the wrong combo could dampen a drug’s effect … or deliver a heftier dose.
By Lindsay Moyer, Center for Science in the Public Interest
| With Joseph Boullata, professor of clinical nutrition at Drexel University and a pharmacy specialist at the Hospital of the University of Pennsylvania.
Q: [Lindsay Moyer] How can a food interfere with a drug?
A: [Joseph Boullata] Sometimes, it’s because of similarities in the way that the body handles foods and drugs. Or it’s because of the chemistry of the food or the drug. For example, taking a drug with a meal can increase or decrease the absorption of the drug.
Q: So the drug might not work?
A: Right. Certain antibiotics, for example, do a great job of binding to minerals like calcium. When the antibiotic does that, it’s not going to be completely absorbed. And neither is the calcium.
That’s a big deal if somebody is taking an antibiotic for an infection. I remember a patient who had a urinary tract infection and was taking one of those antibiotics—ciprofloxacin—and nobody had told her how to take it.
She was taking it with yogurt every day. The infection didn’t get better, and then became resistant to the antibiotic. Eating yogurt a few hours later would have been fine.
Q: How can foods interfere with how the body handles drugs? …
A: Grapefruit juice is a good example. It contains a number of compounds that can destroy one of the main enzymes, cytochrome P450 3A4.
If that happens, any drug that would normally be metabolized by that enzyme—which is about 50 percent of all the drugs we have—wouldn’t be fully metabolized. That would increase the amount of drug in the body.
Q: Why do labels on many drugs say to avoid alcohol?
A: Alcohol can affect the central nervous system, the liver, and the kidneys. So, for example, if somebody is taking an antidepressant that also affects the central nervous system, alcohol may amplify the drug’s side effects …
Q: Do people on some blood pressure drugs have to avoid potassium-rich foods?
A: Most people don’t have to worry. One group of medications causes your body to hold on to potassium. Those are drugs like ACE inhibitors, angiotensin II receptor blockers, and potassium-sparing diuretics … Read more.
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