Most adults who take medication know that certain foods can interact – in a bad way – with certain drugs. But they may not know the full extent of the danger.
One harmful interaction familiar to many is grapefruit juice and cholesterol-lowing statins. However, people may be surprised to learn that grapefruit juice should be avoided while taking many other types of medications; more on that later.
Food has an effect on drug intake in several ways:
- Absorption. Drugs are absorbed by passing from the GI tract into the blood. Food can interfere with drug absorption, making the drug less effective. For this reason, some drugs should not be taken with any type of food. On the other hand, some drugs should be taken with food, to avoid stomach irritation.
- Breakdown. When a drug is taken, it is metabolized – the body alters its chemistry. Certain foods act to enhance or inhibit the metabolism process.
- Excretion. All drugs are eventually eliminated from the body; in most cases the excretion is by the kidneys in urine. This process may be affected by food and the nutrients it contains.
Mark Frankenberger is a Doctor of Pharmacy and the pharmacy manager of Corey’s, a Vero Beach institution since 1956. From his perspective, one of the most significant food/drug interactions is that of green leafy vegetables with the blood-thinning drug warfarin (the most common brand name is Coumadin).
Green leafy vegetables include kale, spinach, collards, turnips, broccoli and chard. These greens are high in Vitamin K and can decrease the ability of blood thinners to prevent clotting. It’s not necessary to give up the greens completely, but problems arise when there is a sudden increase or decrease in intake, so the advice is to keep consumption at consistent levels.
“We see fewer and fewer patients on Coumadin,” Dr. Frankenberger says. “There are other drugs that thin the blood that don’t require a modification in diet, but those drugs have significantly higher cost, so there’s a trade-off.”
Other common food/drug interactions include:
- Salt substitutes interact with digoxin and ACE inhibitors. Salt substitutes often replace sodium with potassium. An increase in potassium can decrease the effectiveness of digoxin, a heart failure medication. ACE inhibitors, taken for high blood pressure, contain potassium, so using salt substitutes can lead to an unhealthy increase in blood potassium levels.
- Natural black licorice interacts with digoxin, blood pressure medication and blood-thinning drugs. Glycyrrhiza is natural ingredient used to make black licorice. It is known to deplete the body of potassium while causing an increased retention of sodium. This can strengthen the effect of the heart medicine digoxin, and cause the heart to beat improperly. Glycyrrhiza can also decrease the effectiveness of blood pressure medications; another effect is to increase the body’s clotting mechanism, which is in direct conflict with the purpose of blood thinning drugs.
- Tyramine interacts with MAOIs and Parkinson medication. High levels of the amino acid tyramine in the blood can increase blood pressure. Certain medications interfere with the breakdown of tyramine, including monoamine oxidase inhibitors (used to treat depression) and drugs used to treat the symptoms of Parkinson’s disease. Those taking these drugs should avoid foods high in tyramine to avoid high blood pressure; the list includes hot dogs, smoked meats, aged meats and cheeses, processed lunch meats, fermented soy products, chocolate and draft beer.
- Grapefruit juice interacts with many medications. Grapefruit juice increases the absorption of a number of cholesterol-lowering statin drugs. While increased absorption may sound like a good thing, it’s not – too much of a drug is just as bad as too little. Grapefruit juice can also cause the body to metabolize other drugs abnormally, resulting in too-high or too-low blood levels of the drug. Many other medications are affected in this way – including blood pressure drugs, antihistamines, thyroid replacement drugs, stomach acid-blocking drugs and the cough suppressant dextromethorphan. The best advice is to avoid grapefruit juice completely if taking any of these drugs.
The risk for harmful food and drug interactions can be affected by age, gender, medical history, number and type of medications used, body weight and nutritional status.
Special attention should be paid to alcohol, as it can interact badly with scores of prescription medications. Examples of commonly used medications with serious alcohol interactions include:
- Heart medications. Alcohol can cause a rapid heartbeat and sudden changes in blood pressure.
- NSAIDs (non-steroidal anti-inflammatory drugs): Alcohol can increase risk of ulcers and stomach bleeding.
- Blood thinning medications. Alcohol can lead to internal bleeding.
- Sleep medications. Alcohol can cause impaired breathing, problems with motor control and unusual behavior.
In addition to these chemical interactions, Dr. Frankenberger says that you should avoid alcohol if you are taking any drug that could make you dizzy or throw off your balance. And just because a medication is over-the-counter doesn’t mean it’s safe to take with alcohol – many non-prescription medications also have undesirable alcohol interactions, including those taken for colds, coughs, fever, and nausea.
We also need to talk about coffee. While it has known health benefits, it can also interfere with how some medications work, including anti-depressants, thyroid medication and osteoporosis drugs. Fortunately, the guidance isn’t to give up your morning (or afternoon) coffee, but to take those medications at a different time of the day.
Dr. Frankenberger says some people are extra-sensitive to caffeine. “People with a heart condition, for example arrhythmia, should be careful about their caffeine intake, especially if they have this sensitivity.”
It’s a good idea to check with your doctor or pharmacist about possible food interactions before you begin taking any new medication. And since prescriptions may be written by different doctors or filled at different pharmacies, make sure the person you talk to knows about all of your medications so they can provide guidance with the whole picture in mind. And even though an adverse interaction between food and over-the-counter medications is rare, it doesn’t hurt to let them know if f you are taking any medications of that type.
Prescription medicines come with directions on when (AM or PM) and how (full stomach, empty stomach) to take them. While it may be a little inconvenient to take exactly as directed, the benefit of maximum effectiveness far outweighs the bit of bother.
Corey’s Pharmacy is located at 2912 Ocean Drive on the barrier island; the phone number is 772-231-6931.
