Foods that interact with medications

-Dr.Dianne McCallister, Chief Medical Officer at Centura's Porter Adventist Hospital

Did you know that your morning grapefruit or a nightly cocktail might change the way your medications work?  

There are two basic reasons that foods interact with our medications:
First, most medications are taken orally - and they interact with foods in our digestive system.

A second reason is that there are some foods that contain high levels of vitamins that interfere with how a drug acts in the body.

Common Food Interactions

Milk interferes with the absorption of the tetracycline drugs- so dairy products should not be consumed in the 2 hours before or after taking the medication.

Oatmeal affects the drug digoxin, so should not be taken at the same time
Any food interferes with the absorption of bisphosphonates - taken for osteoporosis.

In addition, many other drugs are not absorbed well when taken with food

Vitamin interference

The drug warfarin (Coumadin) acts by inhibiting the bodies use of Vitamin K, thereby making the blood less likely to clot - or "thinner" and is used to prevent heart attacks, strokes, and blood clots in the legs.

Foods that contain a lot of Vitamin K - green leafy vegetables, brussel sprouts and broccoli in particular - can interfere with the drug and increase the chance of forming clots.

Another problem involves drugs called MAO inhibitors. Foods such as certain cheeses containing high levels of the amino acid tyramine. Tyramine interacts with the drug to produce changes in blood pressure that can be fatal.

Grapefruit Juice

Grapefruit juice  can interact with a large number of medications to slow down the metabolism of the meds - thereby increasing the effect of the medication - a few examples include estrogen, statins used for cholesterol lowering, blood thinners, blood pressure drugs and the antidepressant triazolam.
More than 85 medications have side effects caused by grapefruit.
For the entire list, visit


Alcohol is a depressant and can lead to respiratory depression - or death - when consumed with drugs that have a sedative effect.

How To Avoid Negative Interactions

Fortunately, your physician should review this with you when prescribing the medication, and in addition, the pharmacy puts labels on your prescriptions, and gives you information explaining how to take the medication (for example on an empty stomach) and particular foods to avoid while taking the medication.

It is extremely important to read and follow these instructions.

In addition - remember that there are reactions between supplements and other medications or foods, so be sure and read the labels on anything over the counter that you take.

If you have questions, your pharmacy  has a program that will check for interactions for you.

Finally - there are websites that give information. They include:




Dr. McCallister is on 7NEWS at 11 a.m. every Wednesday. If you have a topic or question you would like her to discuss, email .

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