Foods that don’t pair well with meds

By John Murphy, MDLinx
Published March 14, 2019

Key Takeaways

What patients eat and drink can affect the way their prescription medicines work. During a hectic day with a hefty caseload, it can be easy to forget to mention some of these details or just as easy for patients to forget you’ve mentioned it. So, here’s a refresher—with some updated information—to help you emphasize these important food-drug interactions.

Grapefruit juice and statins

The warning against drinking grapefruit juice while taking statins is well known, but you might not know the whole story.

Certain statins—atorvastatin, lovastatin, and simvastatin—carry noticeable warnings in their prescribing information: “Avoid grapefruit juice with simvastatin,” for example. The reason for this warning is that grapefruit juice can increase the risk of the drug’s side effects, notably myopathy—which includes the rare and potentially fatal side effect of rhabdomyolysis.

But, take note that grapefruit juice increases a statin’s side effects because it increases the bioavailability of the drug in the body. More drug equals greater risk of side effects. But this also means a more powerful effect from the drug.

In fact, researchers reported in The American Journal of Medicine that drinking a glass of grapefruit juice with 40 mg of either simvastatin or lovastatin increased the effective dose of the drug by 3.6-fold. Even when the grapefruit juice was consumed 12 hours before taking either drug, there was a 1.9-fold increase.

“The expected effect of grapefruit juice consumption is to increase the reduction of LDL cholesterol by up to about 6 percentage points, with a similar reduction in the incidence of [ischemic heart disease],” the authors wrote. “It would be perverse to regard this enhanced efficacy as an adverse effect. Even with the small risk of rhabdomyolysis, there is a net health benefit.”

Overall, there is no need to advise people taking statins to avoid drinking grapefruit juice, these authors concluded.

Bananas and ACE inhibitors

Angiotensin converting enzyme (ACE) inhibitors—such as captopril, enalapril, and lisinopril—dilate the blood vessels to lower hypertension or treat heart failure.

ACE inhibitors can increase the amount of potassium in the body and disrupt the potassium balance. Potassium is critically involved in electric signal functioning of the heart. Too much potassium can interfere with this electrical signaling in the myocardium, causing arrhythmia and heart palpitations. So, people taking ACE inhibitors should avoid eating large amounts of foods high in potassium, such as bananas. Other foods high in potassium include avocados, beets, oranges and orange juice, potatoes, spinach, tomatoes and tomato sauce, as well as salt substitutes.

Kale and warfarin

Vitamin K is essential for proper blood-clotting. But individuals who are at risk for harmful blood clots—the kind that cause heart attack, stroke, deep vein thrombosis, or pulmonary embolism—are prescribed anticoagulants like warfarin.

Warfarin decreases the activity of vitamin K, which inhibits the formation of harmful blood clots. Leafy greens, such as kale and spinach, have a lot of vitamin K. Eating a large serving of food high in vitamin K can decrease the anticoagulative effects of warfarin. By the same token, suddenly lowering your vitamin K intake can amplify these effects. Ideally, it’s best to keep vitamin K intake as consistent as possible. So, if you don’t want to give up kale, spinach, or other foods rich in vitamin K, at least eat them regularly and in the same amounts.

Black licorice and digoxin

Digoxin—a glycoside drug used for treating heart failure and atrial fibrillation—works by slowing down the flow of sodium and potassium in and out of myocardial cells. This results in a strengthening of heart muscle, which, in turn, improves its ability to pump blood. Digoxin also slows down the electrical signals that control the heart rate to help restore a normal, steady heart rhythm.

Black licorice contains the compound glycyrrhizin, which is derived from licorice root and used as a sweetener and flavoring in some candies, cakes, and other foods and beverages. Glycyrrhizin can elevate sodium levels and reduce potassium levels. People who consume too much glycyrrhizin—from an overindulgence in black licorice or from taking licorice root dietary supplements– can develop abnormal heart rhythm, high blood pressure, swelling, lethargy, or congestive heart failure.

“If you’re 40 or older, eating 2 ounces of black licorice a day for at least 2 weeks could land you in the hospital with an irregular heart rhythm or arrhythmia,” according to a warning from the FDA.

However, most licorice candy sold in the United States contains little or no actual licorice, the FDA advised. Also, licorice root supplements that have had the glycyrrhizin removed are available.

Cheese and MAOIs

Strong and aged cheeses—such as aged cheddar, Swiss, Parmesan, Camembert, and blue cheeses like Stilton and Gorgonzola—have high levels of tyramine, an amino acid that helps regulate blood pressure. Foods that contain protein also contain small amounts of tyramine, and tyramine levels increase in aged foods. Tyramine-rich foods include not only aged cheeses, but also cured and smoked meats, pickles, sauerkraut, tap beer, red wine, and chocolate in excessive amounts.

Monoamine oxidase inhibitors (MAOIs) are typically used for treatment-resistant depression. They block monoamine oxidase, an enzyme that breaks down excess amounts of tyramine in the body, and thus relieves depression. Eating foods high in tyramine while taking MAOIs can cause hypertensive crisis—a dangerous, emergency-level spike in blood pressure.

On a brighter note, the use of MAOIs for depression has decreased as new antidepressants have been developed—so those with chronic depression don’t have to go without their cheese and sliced sausage.

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