Why patient diet is a critical component to medication management

Though some patients are less than diligent in taking their medications, many more are right on top of things. They take their meds on time and refill their prescriptions before they run out. But even if people are eating right, they may not take into consideration what impact even the best diet — let alone the worst — can have on their medications’ effectiveness.

There’s a reason why some meds say “take with food” and others intentionally do not. The nutrients in beverages, food and their very presence in your digestive tract can have a significant impact on many drugs’ effectiveness — weakening or heightening their efficacy or causing harmful side effects.

It’s often not enough to simply prescribe a medication, counting on the average patient to read and follow the label instructions, let alone read the tiny type of an accompanying patient-information leaflet. But there’s also little time in a provider’s overcrowded day to discuss these things in a too-brief office visit.

That’s why in the RxLive medication-management consults we drill down to what a patient regularly eats and drinks, and when, along with what vitamins, supplements and other over-the-counter medications they might forget to mention in an office visit. These issues are right at the center of our clinical pharmacists’ focus and training, which is why adding the consultative eyes and ears of a pharmacist is vital to maximizing the value your team brings in optimizing your patients’ health.

During March’s National Nutrition Month, it seemed appropriate for me to address this issue and remind providers how to best fill in this education gap for your patients. (See this toolkit for helpful patient handouts and puzzles/activities, press releases and planning materials by the Academy of Nutrition and Dietetics, the month’s sponsor.)

Just as RxLive clinical pharmacists carefully check for possible drug-drug interactions or unnecessary duplication — such as warning against taking too much OTC acetaminophen on top of an opioid that includes acetaminophen — we also discuss the patient’s standard diet of meals and snacks to see what might be negatively affecting the prescriptions you write for them.

Common dietary drug interactions

As the Harvard Medical School has published, there are many foods, drinks or ingredients can interfere with specific drugs…some dangerously:

Alcohol. Not surprisingly, drinking alcohol can interfere with many medications. Alcohol can diminish the effects of erectile dysfunction drugs such as sildenafil (Viagra); cause extreme drowsiness when taken with antihistamines such as diphenhydramine (Benadryl); cause liver damage in people taking high doses of acetaminophen (Tylenol); increase risk of stomach bleeding when combined with nonsteroidal anti-inflammatory drugs such as ibuprofen (Advil); and even be fatal if mixed with some prescription painkillers, such as oxycodone (Oxycontin) or anxiolytics like alprazolam (Xanax).

Licorice. Yep, that old childhood favorite can be bad for your health, especially for people with diabetes or cardiovascular disease. Black licorice contains glycyrrhizic acid; eating it while taking digoxin (Lanoxin) to treat heart failure may cause an irregular heartbeat and heart attack. The combination increases salt absorption and potassium loss, and it can increase blood pressure as well as blood sugar.

Grapefruit. Eating grapefruit or drinking large amounts of grapefruit juice while taking certain statins to lower cholesterol — such as atorvastatin (Lipitor), lovastatin (Mevacor) or simvastatin (Zocor) — can amplify the effects of the medications and increase the risk of side effects, such as muscle pain and rhabdomyolysis. “But you would need to eat six grapefruits per day,” notes Dr. Randall Zusman, a cardiologist and Harvard associate professor.

Dietary vitamin K. This is a classic food-drug interaction we’d be remiss not to mention. Foods rich in vitamin K  — such as spinach, kale and Brussels sprouts — can make the anticoagulant warfarin (Coumadin) less effective, essentially neutralizing  its mechanism of action for clot prevention.

Dietary potassium. Foods high in potassium, such as bananas and salt substitutes, can boost potassium levels. That can cause an irregular heartbeat for persons taking drugs that raise potassium in the body. These include certain angiotensin-converting enzyme (ACE) inhibitors such as lisinopril (Prinivil), angiotensin-receptor blockers (ARBs) such as valsartan (Diovan), and aldosterone-receptor blockers such as eplerenone (Inspra).

Salt. Eating foods with lots of sodium or salt can nullify the effects of diuretics, ACE inhibitors, ARBs and aldosterone-receptor blockers. “Those drugs are dependent on facilitating the loss of salt from your body. If you’re eating salt, you’re preventing the drugs from working the way they should,” Dr. Zusman states.

Sugar and carbohydrates. Eating foods with added sugar or too many carbohydrate-rich foods (bread, pasta, rice) can cause blood sugar to spike. That can dampen the effects of drugs that treat diabetes, such as metformin (Glucophage) or insulin. “Those medications reduce blood sugar. If you have more carbs, then the medication may not work as well, so the dose may need to be increased,” explains Joanne Doyle Petrongolo, a pharmacist at Harvard-affiliated Massachusetts General Hospital. Or, better yet, don’t increase the dosage and cut your intake of sugar and carbs!

Patients diagnosed with diabetes will need regular counseling and education on how to best manage their diabetes, especially regarding nutrition since eating foods with added sugar or too many carbohydrates will raise blood sugar.  Many medications that treat diabetes, particularly insulin, may need regular adjusting to account for variations in sugar and carbohydrate intake.

Inform patients on what foods to avoid

I know it’s a challenge to cover all of this in an office visit, though I know you try. But in general, try to periodically remind them to always ask you or their retail pharmacist what foods and drinks they should avoid fully or at least ingest only in moderation. (Retail pharmacists are extremely busy — I know, I’ve been one! — but if reminded, most will do their best. However, the conversation would typically take place in a very public environment, and patients may be reluctant to discuss what they eat or drink or are being prescribed. That’s why we established RxLive so a patient can have our full focus outside of the busy prescription-filling operation, and people can talk to us from the private location of their choice.)

Regardless, patients need to have the conversation with someone, someplace, in addition to regularly updating you of any changes to their medications prescribed by other doctors, or what new “latest thing” they’re starting to take from the aisles of their pharmacy or grocery store.

Patients are encouraged to:

  • Ask their providers or pharmacist about each med (and combination), either when changing potency on an existing med, discontinuing one or adding a new script. What are potential side effects, what food or drinks should they avoid, etc.
  • Don’t buy foods or drinks they should avoid. Once they’re brought into the house, these temptations are hard to resist.
  • Encourage them to keep a list of all meds and supplements, their strength, frequency, what each is for, who prescribed it and, if there’s been a change, include a column noting what had previously been taken in its place. In a perfect world, each of us would have a personal health record including this data that could be securely shared with each provider as the patient desires. But with continuing challenges of multiple EHRs and portal platforms, that’s still in the future for most of us. A colleague of mine keeps a printable spreadsheet or Word table, by disease state, and always dates, prints and takes it to each doctor’s visit. It’s way better than counting on memory when provider visits can be months apart.
  • Take the advice of doctors and pharmacists. They don’t provide that information to make an encounter longer; they do it because it matters.

There are many more suggestions, but you get the idea. I and the other clinical pharmacists and care coordinators on the RxLive team welcome the opportunity to take some of this burden off of your busy staff and your patients’ understaffed retail pharmacies to keep the patients you care for in the best possible health. Click here to get in touch and learn how.

Additional resources on drug and dietary interference

Nutrition information (American Society for Nutrition, multiple scientific articles)

National Nutrition Month Campaign Toolkit

National Nutrition Month Promo Kit (HHS, at health.gov)

Medication Interactions: Food, Supplements and other Drugs (American Heart Association)

Merck Manual, Drug-Nutrient Interactions (provider and consumer versions)

Eating doesn’t have to be boring (American Diabetes Association tips on carbs: starches, sugar and fiber)

Nutrition Therapy for Adults with Diabetes or Prediabetes: 2019 Consensus Report  (ADA; PDF)

Kristen Engelen, PharmD
Kristen Engelen, PharmD, is the chief pharmacy officer of RxLive and a certified consultant pharmacist; she has over a decade of experience in retail pharmacy settings. Kristen became an RxLive co-founder because of her passion for geriatric pharmacy, with a focus on the intersection of pharmacy and aging.